NC-2009 EAp2: Minimum Energy Performance

  • NC EAp2 Credit Req's Diagram
  • Beyond code compliance, but doable

    This prerequisite is a big one, not only because it’s required for all projects, but also because it feeds directly into EAc1: Optimize Energy Performance, where about a fifth of the total available points in LEED are at stake. Master these minimum requirements, and you can use the same compliance path as in EAp2 to earning points.

    You won’t earn the prerequisite by accident, though. Although “energy efficiency” is on everyone’s lips, the mandatory and performance-based requirements for EAp2 go beyond code compliance in most places. That said, there is nothing to stop you from meeting the requirements with a reasonable amount of effort, and the environmental benefits as well as the operational cost savings are significant.

    Most projects start by choosing which of the three available compliance paths to follow. We’ll look at them each in turn.

    Option 1: Energy modeling

    Option 1 alone gives you access to all of the points available through EAc1, and offers the most flexibility in giving you credit for innovative designs.

    First, you need to meet the mandatory requirements of ASHRAE 90.1-2007 for all major components, including the envelope, HVAC, lighting, and domestic hot water. ASHRAE 90.1 has had some changes and new mandatory requirements since the 2004 version, which was referenced on previous LEED systems, so be sure to review the standard carefully.

    Cost of changeEnergy efficiency is an area where it behooves project teams to start early and work together to maximize savings. Playing catch-up later on can be costly.Second, you need to demonstrate a 10% savings (5% for existing buildings) for your designed building compared with a baseline case meeting the minimum requirements of ASHRAE 90.1 (or Title 24-2005, Part 6 for California projects). You do this by creating a computer model following rules described in Appendix G of ASHRAE 90.1.

    Computer modeling offers the following key advantages:

    • It can be used to provide feedback on your design both early on, and as the design progresses, so it’s best to use in this way rather than simply demonstrating compliance.
    • It can help your team focus on the most cost-effective efficiency strategies, by plugging in different options and seeing the results.
    • If your building is unconventional or complex in design, an energy model is the best way to account for that.

    Your building type may not have a choice—you may have to follow this path, because both Options 2 and 3 are prescriptive compliance paths that are only available to specific building types and sizes.

    However, if your building type and size allow, and you don’t want to embark on the complex process of computer modeling, which also requires expert assistance from a modeler or from a member of the mechanical engineer’s team, the prescriptive compliance paths are a good way to earn the prerequisite simply by following a checklist.

    Solar shadingPassive design strategies such as shading to reduce solar heat gain are the most cost-effective ways to improve energy performance.Note, however, that when you get to EAc1, there are a lot fewer points on the table for the prescriptive paths, and that you have to follow each prescriptive requirement. These paths also require more collaboration and focus early on in design than you might think. The design team must work together to integrate all of the prescriptive requirements, and Option 3 even requires documentation of certain design processes.

    Option 2: ASHRAE Advanced Energy Design Guides

    The Advanced Energy Design Guides are published by ASHRAE for office, warehouse, and retail projects less than 20,000 ft2—so if you don’t fall into one of those categories, you’re not eligible for this path.

    These guides outline strategies to reduce energy use by 30% from 2001 levels, or an amount equivalent to approximately 10%–14% reduction from ASHRAE 90.1-2007. If you choose this compliance path, become familiar with the list of prescriptive requirements and commit to meeting all of them.

    Option 3: Advanced Buildings Core Performance Guide

    The Core Performance Guide path is a good option if all of the following are true:

    • your project is smaller than 100,000 ft2,
    • you cannot pursue Option 2 because there is not an ASHRAE guide for the building type,
    • your project is not a healthcare facility, lab, or warehouse,
    • and you would rather not commit to the energy modeling required for Option 1.

    Comply with all requirements within Sections 1 and 2 of the guide. If you choose this path, become familiar with the list of prescriptive requirements and commit to meeting them. Also note that it’s not just a list of prescriptive requirements, but a prescribed process for achieving energy efficiency goals. You must demonstrate that you considered a couple of alternate designs, for example, and that certain team meetings were held.

    Reduce energy loads first

    Energy efficiency offers a clear combination of environmental benefit and benefit to the owner through reduced operational expenses, and potentially reduced first costs, if you’re able to reduce the size and complexity of your HVAC system with a more efficient envelope.

    High-tech HVAC systems, and onsite renewable energy generation are often signature components of green buildings, but consider these strategies more “icing” on the cake, rather than a place to start. Start with building orientation and passive design features first. Also look at envelope design, such as energy-efficient windows, walls and roof, before looking at HVAC and plug loads. A poorly designed envelope with a high-tech HVAC system is not, on the whole, efficient or cost-effective. 

    District energy systems

    Projects connected to district energy systems will not be able to utilize the system efficiencies of the base plant to demonstrate compliance with the prerequisite. They can plan on benefiting from these systems under EAc1, however.

    Look for incentives

    Focusing on energy efficiency and renewable energy generation can seem to add costs to a project, but there are a variety of utility-provided, as well as state, and federal incentives available to offset those premiums. (See Resources.)

  • FAQs for EAp2

    Is it acceptable to model a split-type AC with inverter technology compressor as a heat pump, like modeling VRF?

    Ideally if the software you are using cannot model a technology directly then seek a published workaround related to your software. If you can't find a published workaround then model it as you think it should be modeled and explain how you have modeled it in the preliminary LEED submission.

    A portion of our building envelope is historic. Can we exclude it from our model?

    No, not if it is part of the LEED project. However, there is an exemption for existing building envelopes in Appendix G that allow you to model the existing condition in the baseline so you do not pay a penalty.

    For an existing building, do I need to rotate the model?

    No, not for an existing building.

    Our project has a large process load—75%. Despite our efforts to make an efficient HVAC design, the cost savings are minimal. What can we do to earn this prerequisite and be eligible for LEED certification? Is there any flexibility in how we model the process load?

    You must model accurately. Since you don't have enough savings in the building energy, find savings in the process. Either you will be able to demonstrate that compared to a conventional baseline the process being installed into the factory is demonstrably better than "similar newly constructed facilities," allowing you to claim some savings, or the owner needs to install some energy-saving measures into the process to get the project the rest of the way there. Either option can be difficult, but not impossible.

    Account for process load reductions through the exceptional calculation method. A baseline must be established based on standard practice for the process in your location. Any claim of energy savings needs a thorough narrative explaining the baseline and the strategy for energy savings along with an explanation of how the savings were calculated.

    Our process load is higher than 25%. Do we have to justify that?

    It is common to have a 80%–90% process load in a manufacturing facility. The 25% default in LEED is based on office buildings. If you think your load is lower than 25%, it is recommended that you explain why in a short narrative. It is also recommended to briefly explain it if your load is 25% exactly, since that level commonly reveals that the process loads were not accurately represented.

    Do the required savings for this prerequisite (and credit) need to come only from building energy, or also process loads?

    The energy savings are based on the whole building energy use—building and process. LEED does not stipulate exactly where they come from.

    Our local code references ASHRAE 90.1-2010. Should I use that for my documentation, or 90.1-2007?

    For LEED 2009 you'll need touse 90.1-2007. There were some significant changes in 90.1-2010—too many to account for in your LEED review, and your project would also have a much harder time demonstrating the same percentage energy savings.

    Our project doesn't have enough energy savings to earn the prerequisite. Can we get there by incorporating onsite renewables?

    Yes according to LEED, although it is not recommended as a best practice, and it is usually more cost-effective to invest in energy savings in the building.

    Can I claim exterior lighting savings for canopy lighting even though a baseline model cannot include shading elements?

    You can assume exterior lighting savings for canopies against the baseline, but not the shading effects of canopies.

    The project is built on a site with existing exterior lighting installed. How should this be accounted for?

    If exterior lighting is present on the project site, consider it as a constant in both energy model cases.

    Can mezzanines open to floors below be excluded from the energy model?

    Any conditioned area must be included in the energy model.

    How do I provide a zip code for an international location?

    The Energy Star portion of the form does not apply to international projects.

    For a project outside the U.S., how do I determine the climate zone?

    Use the tables and definitions provided in 90.1 Appendix B to determine an equivalent ASHRAE climate zone.

    For a project outside the U.S., how do I determine the Target Finder score?

    International projects are not required to enter a Target Finder score. Target Finder is based on U.S. energy use data.

    Do hotel rooms need automatic light shut-off control?

    For Section 9.4.1.1c, a manual control device would be sufficient to comply with mandatory provisions.

    How commonly are the 90.1 mandatory compliance forms submitted as part of EAp2/EAc1?

    Submitting these forms is not common; however, it can be beneficial if you are applying for any exceptions.

    The Section 9 space-by-space method does not include residential space types. What should I use?

    Use the building area method.

    Can the Passive House Planning Package (PHPP) be used to energy model for LEED?

    Although there is no formal list of approved simulation tools, there are a few requirements per G2.2.1, including the ability of the program to provide hourly simulation for 8760 hours per year, and model ten or more thermal zones, which PHPP does not meet.

    Can the Trace 700 'LEED Energy Performance Summary Report' by uploaded to LEED Online in lieu of the Section 1.4 tables spreadsheet?

    The automated Trace 700 report provides less information than is requested by the Section 1.4 tables spreadsheet. The Section 1.4 tables spreadsheet must be completed.

    Which baseline HVAC system do I use if my building has no heating or air conditioning?

    Assign HVAC systems as per Appendix-G and Section 6 but set thermostatic setpointsSetpoints are normal operating ranges for building systems and indoor environmental quality. When the building systems are outside of their normal operating range, action is taken by the building operator or automation system. out of range so that systems never turn on.

    Our project has a diesel backup generator. Should we include it in our energy model?

    If it is only used for backup and not for regular use such as peak shaving—no.

    Can SHGC be higher in the proposed than in the baseline model?

    SHGC is not a mandatory provision so it is available for trade-off and can be higher than the baseline.

    Do I need to justify the electrical and fuel rates I am using in my model?

    You generally wouldn't need to upload any documentation, but particularly for a non-U.S. project, it may help to provide a short narrative about what they are based on.

Legend

  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip

Pre-Design

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  • Discuss your project’s energy performance objectives, along with how those are shaping design decisions, with the owner. Record energy targets in the Owners Project Requirements (OPR) for the commissioning credits EAp1 and EAc3


  • You won’t earn this prerequisite by accident. The energy efficiency requirements here are typically much more stringent than local codes, so plan on giving it special attention with your team, including leadership from the owner. 


  • Consider stating goals in terms of minimum efficiency levels and specific payback periods. For example: “Our goal is to exceed a 20% reduction from ASHRAE 90.1, with all efficiency measures having a payback period of 10 years or less.”


  • Develop a precedent for energy targets by conducting research on similar building types and using the EPA’s Target Finder program. (See Resources.)


  • For Option 1 only, you will need to comply with the mandatory requirements of ASHRAE 90.1-2007, to bring your project to the minimum level of performance. The ASHRAE 90.1-2007 User’s Manual is a great resource, with illustrated examples of solutions for meeting the requirements.


  • ASHRAE 90.1-2007 has some additional requirements compared with 2004. Read through the standard for a complete update. The following are some samples. 

    • All exterior walls must be installed with rigid insulation of the spans across all floors. This can be accomplished by placing the insulation outside the air barrier. 
    • All exterior doors must be tested for maximum air leakage rate. 
    • All spaces must have independent lighting controls. 
    • Occupancy sensors must be installed in some spaces.
    • The minimum efficiency level of specific mechanical equipment has been raised.  

  • The prerequisite’s energy-reduction target of 10% is not common practice and is considered beyond code compliance. 


  • ClerestoryIndirect sunlight delievered through clerestories like this helps reduce lighting loads as well as cooling loads. Photo – YRG Sustainability, Project – Cooper Union, New York A poorly designed envelope with a high-tech HVAC system is not, on the whole, efficient or cost-effective. Start with building orientation and passive design features first when looking for energy efficiency. Also look at envelope design, such as energy-efficient windows, walls and roof, before looking at HVAC and plug loads. HVAC may also be a good place to improve performance with more efficient equipment, but first reducing loads with smaller equipment can lead to even greater operational and upfront savings. A poorly designed envelope with a high-tech HVAC system is not, on the whole, efficient or cost-effective. 


  • Don’t plan on using onsite renewable energy generation (see EAc2) to make your building energy-efficient. It is almost always more cost-effective to make an efficient building, and then to add renewables like photovoltaics as the “icing” on the cake.


  • Some rules of thumb to reduce energy use are:

    • Program similar spaces together to reduce distribution losses 
    • Use a window-to-wall ratio below 40%, on average
    • Use a window-to-wall ratio below 20% on east and west sides, to reduce low-angle solar gain, and glare; 
    • Reduce direct solar gain with solar shades or building geometry and orientation
    • Distribute heating and cooling loads uniformly throughout all facades for a smaller system size. 
    • Design a tight and well-insulated building envelope to reduce the heating load and improve HVAC performance
    • Use right-sized and efficient heating and cooling systems
    • Consider onsite renewable energy generation.

  • Choosing your compliance path


  • Find the best credit compliance path based on your building type and energy-efficiency targets. Use the following considerations, noting that some projects are more suited to a prescriptive approach than others. 


  • Option 1: Whole Building Energy Simulation requires estimating the energy use of the whole building over a calendar year, using methodology established by ASHRAE 90.1-2007, Appendix G. Option 1 establishes a computer model of the building’s architectural design and all mechanical, electrical, domestic hot water, plug load, and other energy-consuming systems and devices. The model incorporates the occupancy load and a schedule representing projected usage in order to predict energy use. This compliance path does not prescribe any technology or strategy, but requires a minimum reduction in total energy cost of 10% (5% for an existing building), compared to a baseline building with the same form and design but using systems compliant with ASHRAE 90.1-2007. You can earn additional LEED points through EAc1 for cost reductions of 12% and greater (8% for existing buildings). 


  • Option 2: Prescriptive Compliance Path: ASHRAE Advanced Energy Design Guide refers to design guides published by ASHRAE for office, school, warehouse, and retail projects. These guides outline strategies to reduce energy use by 30% from ASHRAE 90.1-2001 levels, or an amount equivalent to a 10%–14% reduction from the ASHRAE 90.1-2007 standard. If you choose this compliance path, become familiar with the list of prescriptive requirements and commit to meeting them. (See the AEDG checklist in the Documentation Toolkit.) 


  • Option 3: Prescriptive Compliance Path: Advanced Buildings Core Performance Guide is another, more basic prescriptive path. It’s a good option if your project is smaller than 100,000 ft2, cannot pursue Option 2 (because there is not an ASHRAE guide for the building type), is not a healthcare facility, lab, or warehouse—or you would rather not commit to the energy modeling required for Option 1. Your project can be of any other building type (such as office or retail). To meet the prerequisite, you must comply with all requirements within Sections 1 and 2 of the guide. If you choose this path, become familiar with the list of activities and requirements and commit to meeting them. (See Resources for a link to the Core Performance Guide and the Documentation Toolkit for the checklist of prescriptive items.)


  • EAc1: Optimize Energy Performance uses the same structure of Options 1–3, so it makes sense to think about the credit and the prerequisite together when making your choice. In EAc1, Option 1 offers the potential for far more points than Options 2 and 3, so if you see your project as a likely candidate for earning those points, Option 1 may be best.


  • Hotels, multifamily residential, and unconventional commercial buildings may not be eligible for either Option 2 or Option 3, because the prescriptive guidance of these paths was not intended for them. Complex projects, unconventional building types, off-grid projects, or those with high energy-reduction goals are better off pursuing Option 1, which provides the opportunity to explore more flexible and innovative efficiency strategies and to trade off high-energy uses for lower ones. 


  • If your project combines new construction and existing building renovation then whatever portion contains more than 50% of the floor area would determine the energy thresholds.


  • Options 2 and 3 are suitable for small, conventional building types that may not have as much to gain from detailed energy modeling with Option 1. 


  • Meeting the prescriptive requirements of Options 2 and 3 is not common practice and requires a high degree of attention to detail by your project team. (See the Documentation Toolkit for the Core Performance Guide Checklist.) These paths are more straightforward than Option 1, but don’t think of them as easy. 


  • Options 2 and 3 require additional consultant time from architects and MEP engineers over typical design commitment, which means higher upfront costs. 


  • Option 1 references the mandatory requirements of ASHRAE 90.1-2007, which are more stringent than earlier LEED rating systems that referred to ASHRAE 90.1-2004.


  • Option 1 energy simulation provides monthly and annual operating energy use and cost breakdowns. You can complete multiple iterations, refining energy-efficiency strategies each time. Payback periods can be quickly computed for efficiency strategies using their additional first costs. A building’s life is assumed to be 60 years. A payback period of five years is considered a very good choice, and 10 years is typically considered reasonable. Consult the OPR for your owners’ goals while selecting your efficiency strategies. 


  • Option 1 energy simulation often requires hiring an energy modeling consultant, adding a cost (although this ranges, it is typically on the order of $0.10–$0.50/ft2 depending on the complexity). However, these fees produce high value in terms of design and decision-making assistance, and especially for complex or larger projects can be well worth the investment. 


  • All compliance path options may require both the architectural and engineering teams to take some time in addition to project management to review the prescriptive checklists, fill out the LEED Online credit form, and develop the compliance document. 


  • Option 1: Whole Building Energy Simulation


  • The architect, mechanical engineer, and lighting designer need to familiarize themselves and confirm compliance with the mandatory requirements of ASHRAE 90.1-2007, sections 5–9.


  • Use simple computer tools like SketchUp and Green Building Studio that are now available with energy analysis plug-ins to generate a first-order estimate of building energy use within a climate context and to identify a design direction. Note that you may need to refer to different software may not be the one used to develop complete the whole building energy simulations necessary for LEED certification. 


  • Energy modeling can inform your project team from the start of design. Early on, review site climate data—such as temperature, humidity and wind, available from most energy software—as a team. Evaluate the site context and the microclimate, noting the effects of neighboring buildings, bodies of water, and vegetation. Estimate the distribution of energy across major end uses (such as space heating and cooling, lighting, plug loads, hot water, and any additional energy uses), targeting high-energy-use areas to focus on during design.  


  • Energy use breakdown pie chartUse a preliminary energy use breakdown like this one to identify target areas for energy savings.Perform preliminary energy modeling in advance of the schematic design phase kick-off meeting or design charrette. The energy use breakdown can help identify targets for energy savings and point toward possible alternatives. 


  • For existing buildings, the baseline energy model can reflect the pre-renovation features like rather than a minimally ASHRAE-compliant building. This will help you achieve additional savings in comparison with the baseline.


  • Projects generating renewable energy onsite should use Option 1 to best demonstrate EAp2 compliance and maximize points under EAc1. Other options are possible but won’t provide as much benefit. Like any other project, model the baseline case as a system compliant with ASHRAE 90.1-2007, using grid-connected electricity, and the design case is an “as-designed” system also using grid-connected electricity. You then plug in 100% onsite renewable energy in the final energy-cost comparison table, as required by the performance rating method (PRM) or the modeling protocol of ASHRRAE 90.1 2007, Appendix G. (Refer to the sample PRM tables in the Documentation Toolkit for taking account of onsite renewable energy.


  • LEED divides energy-using systems into two categories: 

    • (i) Regulated loads. Most prominent systems—space heating, cooling, ventilation and pumps, lighting, and hot water—are regulated by ASHRAE and LEED so are termed “regulated” loads. Your energy model can provide insights into the energy use of all these systems. 
    • (ii) Non-regulated loads are those which are not directly associated with creating a comfortable environment, but with plug loads for machines. These include elevators, kitchen equipment, office equipment, televisions, and activity-oriented lighting, such as in hospitals. Though these are very large energy loads, they are not regulated by ASHRAE 90.1 or by LEED. Energy savings from specifying better equipment is not counted in energy models. It is typically expected that these non-regulated loads contribute to 25% of energy use.

  • The energy model itself will not account for any change in plug loads from the baseline case, even if your project is making a conscious effort to purchase Energy Star or other efficient equipment. Any improvement made in plug loads must be documented separately, using the exceptional calculation methodology (ECM), as described in ASHRAE 90.1-2007. These calculations determine the design case energy cost compared to the baseline case. They are included in the performance rating method (PRM) table or directly in the baseline and design case model. 


  • Besides energy modeling, you may need to use the exceptional calculation methodology (ECM) when any of the following situations occur: 

    • The energy software cannot carry out calculations for a specific systems like natural ventilation or unusual HVAC equipment.
    • Process loads are different in baseline and design cases and can influence total energy cost savings.
    • The proposed design can’t demonstrate savings with the modeling protocol and needs additional calculations. 

  • Some energy-modeling software tools have a daylight-modeling capability. Using the same model for both energy and IEQc8.1: Daylight and Views—Daylight can greatly reduce the cost of your modeling efforts.


  • Option 2: Prescriptive Compliance Path—ASHRAE Advanced Energy Design Guides


  • Provide a copy of the AEDG for office, retail, or warehouse, as applicable, to each team member as everyone, including the architect, mechanical and electrical engineers, lighting designer, and commissioning agents, are responsible for ensuring compliance. These are available to download free from the ASHRAE website. (See Resources.) 


  • Find your climate zone before attempting to meet any detailed prescriptive requirements. Climate zones vary by county, so be sure to select the right one. (See the Documentation Toolkit for a list of climate zones by county.)


  • Develop a checklist of all requirements, and assign responsible team members to accomplish them. Hold a meeting to walk the team through the AEDG checklist for your project’s climate zone. Clarify specific design goals and prescriptive requirements in the OPR for EAp1: Fundamental Commissioning.


  • Early access to the AEDG by each team member avoids last-minute changes that can have cascading, and costly, effects across many building systems. 


  • The AEDG prescriptive requirements include: 

    • a maximum allowable window-to-wall ratio;
    • continuous insulation on the outside of walls;
    • roofs and floor-slab minimum thermal performance;
    • minimum window and door thermal performance;
    • minimum boiler and chiller efficiencies;
    • and mandatory use economizers or heat recovery ventilation.

    If your project team is not comfortable following these guidelines, consider switching to Option 1, which gives you more flexibility. 


  • Although Option 2 is generally lower cost during the design phase than energy modeling, the compliance path is top heavy—it requires additional meeting time upfront for key design members. 


  • Option 3: Prescriptive—Advanced Buildings Core Performance Guide


  • Provide a copy of the New Buildings Institute Advanced Buildings: Core Performance Guide to each team member. The guide is available to download free from the NBI website. (See Resources.) 


  • The guide provides practical design assistance that can be used throughout the design process.


  • Walk your team through the project checklist to clarify design goals and prescriptive requirements. 


  • The guide provides an outline for approaching an energy-efficient design, in addition to a list of prescriptive measures. The first of its three sections emphasizes process and team interaction rather than specific building systems or features. Advise the owner to read through the guide in order to understand what is required of the architect and engineers. 


  • Section 1 in the guide focuses on best practices that benefit the project during the pre-design and schematic design stages, such as analyzing alternative designs and writing the owner’s project requirements (OPR). 


  • Section 2 of the Core Performance Guide describes architectural, lighting, and mechanical systems to be included. Section 3 is not required for EAp2 but includes additional opportunities for energy savings that can earn EAc1 points. 


  • The guide mandates that your team develop a minimum of three different design concepts to select from for best energy use.


  • Though they can be a little daunting at first glance, a majority of the guide’s requirements overlap with other LEED credits, such as EAp1: Fundamental Commissioning, IEQp1: Minimum Indoor Air Quality Performance, and IEQc6.1: Controllability of Systems—Lighting Controls


  • This compliance path is top-heavy due to upfront consultant time, but it provides adequate structure to ensure that your project is in compliance with the prerequisite requirements. For some projects it may be less expensive to pursue than Option 1. 

Schematic Design

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  • The owner should now have finalized the OPR with the support of the architect, as part of the commissioning credits EAp1 and EAc3. The goals identified here will help your team identify energy-reduction and occupant-comfort strategies.


  • Consider a broad range of energy-efficiency strategies and tools, including passive solar, daylighting, cooling-load reduction, and natural ventilation to reduce heating and cooling loads. 


  • Develop the basis of design (BOD) document in conjunction with your mechanical engineer and architect for EAp1: Fundamental Commissioning, noting key design parameters to help strategize design direction as outlined in the OPR. 


  • The OPR and BOD serve the larger purpose of documenting the owner’s vision and your team’s ideas to meet those goals. The BOD is intended to be a work-in-progress and should be updated at all key milestones in your project. Writing the document gives you an opportunity to capture the owner’s goals, whether just to meet the prerequisite or to achieve points under EAc1.


  • Confirm that your chosen compliance path is the most appropriate for your project, and make any changes now. Following a review with the design team and owner, ensure that everyone is on board with contracting an energy modeler for Option 1 or meeting all the prescriptive requirements under Options 2 or 3. 


  • Sometimes teams change from Option 1 to Options 2 or 3 very late in the design phase for various reasons including not realizing the cost of energy modeling. Making that change is risky, though: the prescriptive paths are all-or-nothing—you must comply with every item, without exception. Evaluate each requirement and consult with the contractor and estimator to ensure the inclusion of all activities within project management. 


  • To avoid costly, last-minute decisions, develop a comprehensive, component-based cost model as a decision matrix for your project. The model will help establish additional cost requirements for each energy conservation measure. It will also illustrate cost reductions from decreased equipment size, construction rendered unnecessary by energy conservation measures, and reduced architectural provisions for space and equipment access. (See the Documentation Toolkit for an example.)


  • Use envelope design and passive strategies to reduce the heating and cooling loads prior to detailed design of HVAC systems. Passive strategies can reduce heating and cooling loads, giving the engineer more options, including smaller or innovative systems.


  • Load reduction requires coordinated efforts by all design members including the architect, lighting designer, interior designer, information-technology manager, and owner. 

    • Architects can choose the optimum building orientation, select the appropriate envelope system and design it to be tight, and configure programming to utilize passive strategies as much as possible. 
    • Lighting designers help by harvesting daylight, making appropriate fixture selections, minimizing lighting layouts (fewer fixtures), providing maximum controls and daylight and occupancy sensors to reduce wasted light. 
    • Interior designers are critical for selecting reflective finishes to enhance daylighting and specifying Energy Star appliances. 
    • IT specialists are important, especially in buildings with data centers, for selection of computers and data-processing equipment that reduce the power load as well as cooling. 

  • Involving facilities staff in the design process can further inform key design decisions, helping ensure successful operation and low maintenance costs.


  • Encourage your design team to brainstorm design innovations and energy-reduction strategies. This provides a communication link among team members so they can make informed decisions. 


  • More energy-efficient HVAC equipment can cost more relative to conventional equipment. However, by reducing heating and cooling loads through good passive design, the mechanical engineer can often reduce the size and cost of the system. Reduced system size can save money through:

    • smaller chillers or boilers;
    • smaller fans, used less frequently;
    • smaller pumps and auxiliary systems;
    • smaller ducts;
    • and less square footage devoted to mechanical systems.

  • Review case studies of similar energy-efficient buildings in the same climate to provide helpful hints for selecting energy-efficiency measures. For example, a building in a heating-dominated climate can often benefit from natural ventilation and free cooling during shoulder seasons. (See Resources for leading industry journals showcasing success stories around the country and internationally.)


  • The relationship between first costs and operating costs can be complex. For example, more efficient windows will be more expensive, but could reduce the size and cost of mechanical equipment. A more efficient HVAC system may be more expensive, but will reduce operating costs. Play around with variables and different strategies to get the right fit for the building and the owner’s goals as stated in the OPR.


  • Option 1: Whole Building Energy Simulation


  • Review and confirm compliance with the mandatory requirements of all the relevant sections of ASHRAE 90.1-2007


  • Trust your project’s energy modeling task to a mechanical firm with a proven track record in using models as design tools, and experience with your building type.


  • Contract an energy modeling team for the project. These services may be provided by the mechanical engineering firm on the design team or by an outside consultant. Software used for detailed energy use analysis and submitted for final LEED certification must be accepted by the regulatory authority with jurisdiction, and must comply with paragraph G2.2 of ASHRAE Standard 90.1-2007. Refer to Resources for a list of Department of Energy approved energy-analysis software that may be used for LEED projects.


  • Design team members, including the architect and mechanical engineer at a minimum, need to work together to identify a percentage improvement goal for project energy use over the ASHRAE 90.1-2007-compliant baseline model. The percentage should be at least 10% to meet the prerequisite. 


  • Plan on initiating energy modeling during the design process, and use it to inform your design—preferably executing several iterations of the design as you improve the modeled energy performance. 


  • Ask the modeling consultant to develop an annual energy-use breakdown—in order to pick the “fattest” targets for energy reduction. A typical energy-use breakdown required for LEED submission and ASHRAE protocol includes: 

    • lighting;
    • space heating;
    • space cooling;
    • domestic hot water;
    • additional installed heat recovery, refrigeration, or heat-rejection systems;
    • ventilation fans and auxiliary pumps;
    • and equipment and plug loads. 

  • Identify critical areas in which to reduce loads. For example, in a data center, the plug loads are the largest energy load. Small changes in lighting density might bring down the energy use but represent only a small fraction of annual energy use. 


  • Don't forget that LEED (following ASHRAE) uses energy cost and not straight energy when it compares your design to a base case. That's important because you might choose to use a system that burns natural gas instead of electricity and come out with a lower cost, even though the on-site energy usage in kBtus or kWhs is higher. Generally you have to specify the same fuel in your design case and in the base case, however, so you can't simply switch fuels to show a cost savings


  • Explore and analyze design alternatives for energy use analyses to compare the cost-effectiveness of your design choices. For example, do you get better overall performance from a better window or from adding a PV panel? Will demand-control ventilation outperform increased ceiling insulation?


  • Simple, comparative energy analyses of conceptual design forms are useful ways to utilize an energy model at this stage. Sample scenarios include varying the area of east-facing windows and looking at 35% versus 55% glazing. Each scenario can be ranked by absolute energy use to make informed decisions during the design stage. 


  • If your project is using BIM software, the model can be plugged into the energy analysis software to provide quick, real-time results and support better decisions. 


  • Model development should be carried out following the PRM from ASHRAE 90.1-2007, Appendix G, and the LEED 2009 Design and Construction Reference Guide, Table in EAc1. In case of a conflict between ASHRAE and LEED guidelines, follow LEED.


  • Projects using district energy systems have special requirements. For EAp2, the proposed building must achieve the 10% energy savings without counting the effects of the district generation system. To earn points in EAc1 you can take advantage of the district system’s efficiency, but you have to run the energy model again to claim those benefits (see EAc1 for details). 


  • While you could run the required energy model at the end of the design development phase, simply to demonstrate your prerequisite compliance, you don’t get the most value that way in terms of effort and expense. Instead, do it early in the design phase, and run several versions as you optimize your design. Running the model also gives you an opportunity to make improvements if your project finds itself below the required 10% savings threshold.


  • The baseline model is the designed building with mechanical systems specified in ASHRAE 90.1-2007, Appendix G, for the specific building type, with a window-to-wall ratio at a maximum of 40%, and minimally code-compliant specifications for the envelope, lighting, and mechanical components. It can be developed as soon as preliminary drawings are completed. The baseline is compared to the design case to provide a percentage of reduction in annual energy use. To avoid any bias from orientation, you need to run the baseline model in each of the four primary directions, and the average serves as your final baseline figure. 


  • The design-case is modeled using the schematic design, orientation, and proposed window-to-wall ratio—¬the model will return design-case annual energy costs. Earn points by demonstrating percentage reductions in annual energy costs from the design to the baseline case. EAp2 is achieved if the design case is 10% lower than the baseline in new construction (or 5% less in existing building renovations). 


  • Provide as much project and design detail to the modeler as possible. A checklist is typically developed by the energy modeler, listing all the construction details of the walls, roof, slabs, windows, mechanical systems, equipment efficiencies, occupancy load, and schedule of operations. Any additional relevant information or design changes should be brought to the modeler’s attention as soon as possible. The more realistic the energy model is, the more accurate the energy use figure, leading to better help with your design.


  • Invite energy modelers to project meetings. An experienced modeler can often assist in decision-making during design meetings, even without running complete models each time. 


  • All known plug loads must be included in the model. The baseline and design-case models assume identical plug loads. If your project is deliberately attempting to reduce plug loads, demonstrate this by following the exceptional calculation method (ECM), as described in ASHRAE 90.1-2007, G2.5. Incorporate these results in the model to determine energy savings. 


  • For items outside the owner’s control—like lighting layout, fans and pumps—the parameters for the design and baseline models must be identical.


  • It can take anywhere from a few days to a few weeks to generate meaningful energy modeling results. Schedule the due dates for modeling results so that they can inform your design process.


  • Review the rate structure from your electrical utility. The format can inform your team of the measures likely to be most effective in reducing energy costs, especially as they vary over season, peak load, and additional charges beyond minimum energy use.


  • Performing a cost-benefit analysis in conjunction with energy modeling can determine payback times for all the energy strategies, helping the iterative design process.


  • Using energy modeling only to check compliance after the design stage wastes much of the value of the service, and thus your investment.


  • Option 2: Prescriptive—ASHRAE Advanced Energy Design Guides 


  • The architect and mechanical engineer should carefully read the applicable ASHRAE Advanced Energy Design Guide for office, warehouse, or retail projects, as applicable. 


  • Keep the owner abreast of the design decisions dictated by the standard. Fill in the team-developed checklist, within the climate zone table’s prescribed requirements, with appropriate envelope improvements, system efficiencies, and a configuration that meets the standard requirements. 


  • As a prescriptive path, this option relies heavily on following the requirement checklist, which is used throughout the design process to track progress. To assist design development, provide all critical team members—not limited to the architect, mechanical and electrical engineers, and lighting designer—with a checklist highlighting their appointed tasks.


  • The architect, mechanical engineer, and lighting designer need to discuss each requirement and its design ramifications. Hold these meetings every six to eight weeks to discuss progress and make sure all requirements are being met.


  • Confirm that your project team is comfortable with following all the prescribed requirements. If not, switch to Option 1: Whole Building Energy Simulation. 


  • The LEED Online credit form does not specify how to document each prescriptive requirement because they are so different for each project; it only requires a signed confirmation by the MEP for meeting AEDG requirements. You still have to provide documentation. Submit your checklist of requirements, and supporting information for each item, through LEED Online to make your case. If your project fails to meet even one requirement, it will fail to earn the prerequisite, thus jeopardizing LEED certification.  


  • Although energy modeling consultant costs are avoided by this option, additional staff time will be required to document and track compliance status, as compared with conventional projects.


  • Energy efficiency measures prescribed by the guide can be perceived as additional costs in comparison with conventional projects. However, they are easy to implement and are cost-effective pn the whole.


  • Option 3: Prescriptive Compliance Path—Advanced Buildings Core Performance Guide 


  • Become familiar with the Core Performance Guide early in the design phase to know the multiple requirements and all requisite documents.


  • Note that the guide demands additional time, attention, and integrated process from the design team as compared to conventional projects. It’s not just a list of prescriptive requirements, but a prescribed process for achieving energy efficiency goals. LEED Online documentation requires proof of all steps outlined in Sections 1 and 2, including three conceptual design options and meeting minutes. The project manager, architect, and mechanical engineer should read the complete Core Performance Guide carefully to know beforehand the prescriptive requirements in Sections 1 and 2. 


  • The project manager must take responsibility for ensuring that the requirement checklist is on track.


  • For Section 3, the design team needs to identify three or more of the listed strategies as possible targets for the project. 


  • Create a checklist of requirements and assign a responsible party to each item. 


  • The Core Performance Guide requires an integrated design contributed by the architect, mechanical and electrical engineers, and lighting designer. The project manager must take responsibility for shepherding and documenting the collaborative process to demonstrate compliance. 


  • A long documentation list can be overwhelming for your team, so create a detailed checklist with tasks delegated to individual team members, allowing each member to focus on assigned tasks. The checklist can function as a status tracking document and, finally, the deliverable for LEED Online.

Design Development

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  • The architect and engineer, and other project team members, continue to develop a high-performance building envelope with efficient mechanical and lighting systems. 


  • Constant communication and feedback among project team members, owner, and if possible, operational staff, during design development can minimize construction as well as operational costs and keep your project on schedule. 


  • If you change or go through value-engineering on any specifications, such as the solar-heat gain coefficient of glazing, for example, be aware of impacts on mechanical system sizing. Making changes like this might not pay off as much as it first appears.


  • Consider using building information modeling (BIM) tools to keep design decisions up to date and well documented for all team members.


  • Schedule delays can be avoided if all team members share their ideas and update documents during the design development process. 


  • Option 1: Whole Building Energy Simulation


  • The modeler completes the energy analysis of the selected design and system and offers alternative scenarios for discussion. The modeler presents the energy cost reduction results to the team, identifying the LEED threshold achieved.


  • It’s helpful for the energy modeling report to include a simple payback analysis to assist the owner in making an informed decision on the operational savings of recommended features. 


  • The architect and HVAC engineer should agree on the design, working with the cost estimator and owner.


  • Demonstrating reductions in non-regulated loads requires a rigorous definition of the baseline case. The loads must be totally equivalent, in terms of functionality, to the proposed design case. For example, reducing the number of computers in the building does not qualify as a legitimate reduction in non-regulated loads. However, the substitution of laptops for desktop computers, and utilization of flat-screen displays instead of CRTs for the same number of computers, may qualify as a reduction.


  • Residential and hospitality projects that use low-flow showers, lavatories, and kitchen sinks (contributing to WEp1) benefit from lower energy use due to reduced overall demand for hot water. However, for energy-savings calculations, these are considered process loads that must be modeled as identical in baseline and design cases, or you have the choice of demonstrating the savings with ECM for process loads. 


  • Perform daylight calculations in conjunction with energy modeling to balance the potentially competing goals of more daylight versus higher solar-heat gain resulting in high cooling loads. 


  • If your project is pursuing renewable energy, the energy generated is accounted for by using the PRM. These results provide information about whether the energy is contributing to EAc2: Onsite Renewable Energy. 


  • A cost-benefit analysis can help the owner understand the return on investment of big-ticket, energy-conserving equipment that lowers operating energy bills with a quick payback. 


  • Complete at least half of the energy modeling effort by the end of the design development stage. Help the design team to finalize strategy through intensive, early efforts in energy modeling. Once the team has a design direction, the modeler can develop a second model during the construction documents phase for final confirmation. 


  • If pursuing ECM for non-regulated loads, calculate energy saving for each measure separately if you are, for example, installing an energy-efficient elevator instead of a typical one so that the reduction would contribute to total building energy savings. Calculate the anticipated energy use of the typical elevator in kBTUs or kWh. Using the same occupancy load, calculate the energy use of the efficient elevator. Incorporate the savings into design case energy use within the PRM. Refer to the ECM strategy for detailed calculation guidelines. 


  • Option 2: Prescriptive Compliance Path—ASHRAE Advanced Energy Design Guides 


  • Ensure that all prescriptive requirements are incorporated into the design by the end of the design development stage.


  • Revisit the Advanced Energy Design Guides (AEDG) checklist to ensure that the design meets the prescriptive requirements.


  • Option 3: Prescriptive Compliance Path—Advanced Buildings Core Performance Guide


  • The mechanical engineer, lighting consultant, and architect revisit the checklist for an update on the requirements and how they are being integrated into the design. All prescriptive requirements should be specifically incorporated into the design by the end of the design development phase. 


  • The mechanical engineer and architect track the status of each requirement.


  • While the LEED Online credit form does not require detailed documentation for each Core Performance Guide requirement, it is important that each item be documented as required and reviewed by the rest of the team to confirm compliance, especially as further documentation may be requested by during review. Your design team should work with the owner to identify cost-effective strategies from Section 3 that can be pursued for the project. 

Construction Documents

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  • Construction documents clearly detail the architectural and mechanical systems that address energy-efficiency strategies.  


  • Confirm that specifications and the bid package integrate all equipment and activities associated with the project. 


  • If the project goes through value engineering, refer to the OPR and BOD to ensure that no key comfort, health, productivity, daylight, or life-cycle cost concerns are sacrificed.


  • During the budget estimating phase, the project team may decide to remove some energy-saving strategies that have been identified as high-cost items during the value-engineering process. However, it is very important to help the project team understand that these so-called add-ons are actually integral to the building’s market value and the owner’s goals. 


  • Removing an atrium, for example, due to high cost may provide additional saleable floor area, but may also reduce daylight penetration while increasing the lighting and conditioning loads.  


  • Option 1: Whole Building Energy Simulation


  • Although this prerequisite is a design-phase submittal, it may make sense to submit it, along with EAc1, after construction. Your project could undergo changes during construction that might compel a new run of the energy model to obtain the latest energy-saving information. Waiting until the completion of construction ensures that the actual designed project is reflected in your energy model.


  • Create a final energy model based completely on construction document drawings—to confirm actual energy savings as compared to ASHRAE 90.1-2007 requirements. An energy model based on the construction documents phase will provide realistic energy-cost savings and corresponding LEED points likely to be earned. 


  • Make sure the results fit the LEED Online credit form requirements. For example, the unmet load hours have to be less than 300 and process loads will raise a red flag if they’re not approximately 25%. If any of the results are off mark, take time to redo the model. Time spent in design saves more later on in the LEED review process. 


  • Option 2: Prescriptive Compliance Path—ASHRAE Advanced Energy Design Guides


  • Finalize all design decisions and confirm that you’ve met all of the prescriptive requirements. Your team must document the checklist with relevant project drawings, including wall sections, specifications, and the MEP drawing layout.


  • Value engineering and other factors can result in design changes that eliminate certain energy features relevant to the prerequisite. As this compliance path is prescriptive, your project cannot afford to drop even one prescribed item.


  • Option 3: Prescriptive Compliance Path—Advanced Buildings Core Performance Guide


  • Finalize all design decisions and confirm that you’ve met all of the prescriptive requirements. Your team must document the checklist with relevant project drawings, including wall sections, specifications, and the MEP drawing layout.


  • Value engineering and other factors can result in design changes that eliminate certain energy features relevant to the credit. As this compliance path is prescriptive, your project cannot afford to drop even one listed item. Although perceived as high-cost, prescriptive requirements lower energy costs during operation and provide a simple payback structure. 

Construction

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  • The architect and mechanical engineer review the shop drawings to confirm the installation of the selected systems. 


  • The commissioning agent and the contractor conduct functional testing of all mechanical equipment in accordance with EAp1: Fundamental Commissioning and EAc3: Enhanced Commissioning. 


  • Find your Energy Star rating with EPA’s Target Finder tool if your building type is in the database. Input your project location, size, and number of occupants, computers, and kitchen appliances. The target may be a percentage energy-use reduction compared to a code-compliant building, or “anticipated energy use” data from energy model results. Add information about your fuel use and rate, then click to “View Results.” Your Target Finder score should be documented at LEED Online.


  • Plan for frequent site visits by the mechanical designer and architect during construction and installation to make sure construction meets the design intent and specifications. 


  • Emphasize team interaction and construction involvement when defining the project scope with key design team members. Contractor and designer meetings can help ensure correct construction practices and avoid high change-order costs for the owner. 


  • Subcontractors may attempt to add a premium during the bidding process for any unusual or unknown materials or practices, so inform your construction bidders of any atypical design systems at the pre-bid meeting.


  • Option 1: Whole Building Energy Simulation


  • The energy modeler ensures that any final design changes have been incorporated into the updated model.


  • Upon finalizing of the design, the responsible party or energy modeler completes the LEED Online submittal with building design inputs and a PRM result energy summary. 


  • Although EAp2 is a design phase submittals, it may make sense to submit it (along with EAc1) after construction. Your project could undergo changes during construction that might require a new run of the energy model. Waiting until the completion of construction ensures that your actual designed project is reflected. On the other hand, it gives you less opportunity to respond to questions that might come up during a LEED review. 


  • Include supporting documents like equipment cut sheets, specifications and equipment schedules to demonstrate all energy efficiency measures claimed in the building. 


  • It common for the LEED reviewers to make requests for more information. Go along with the process—it doesn’t mean that you’ve lost the credit. Provide as much information for LEED Online submittal as requested and possible. 


  • Option 2: Prescriptive Compliance Path—ASHRAE Advanced Energy Design Guides (AEDG)


  • The design team completes the LEED Online documentation, signing off on compliance with the applicable AEDG, and writing the narrative report on the design approach and key highlights.


  • During LEED submission, the project team needs to make an extra effort to support the prerequisite with the completed checklist and the required documents. Although the LEED rating system does not list detailed documentation, it is best practice to send in supporting documents for the prescriptive requirements from the AEDG. The supporting documents should include relevant narratives, wall sections, mechanical drawings, and calculations. 


  • Although the LEED Online sign-off does not include a checklist of AEDG requirements, it assumes that the team member is confirming compliance with all detailed requirements of the guide. 


  • Option 3: Prescriptive Compliance Path—Advanced Building Core Performance Guide


  • The design team completes the LEED Online credit form, signing off on compliance with the Core Performance Guide, and writing the narrative report on the design approach and key highlights.


  • During LEED submission, your project team needs to make an extra effort to support the prerequisite with the completed checklist and the required documents. Although not every requirement may be mentioned in the LEED documentation, the supporting documents need to cover all requirements with narratives, wall sections, mechanical drawings, and calculations. 


  • Many of this option’s compliance documents are common to other LEED credits or design documents, thus reducing duplicated efforts. 

Operations & Maintenance

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  • Develop an operations manual with input from the design team in collaboration with facility management and commissioning agent if pursuing EAc3: Enhanced Commissioning. 


  • The benefit of designing for energy efficiency is realized only during operations and maintenance. Record energy use to confirm that your project is saving energy as anticipated. If you are not pursuing EAc5: Measurement and Verification, you can implement tracking procedures such as reviewing monthly energy bills or on-the-spot metering.


  • Some energy efficiency features may require special training for operations and maintenance personnel. For example, cogeneration and building automation systems require commissioning and operator training. Consider employing a trained professional to aid in creating operation manuals for specialty items. 


  • Energy-efficiency measures with a higher first cost often provide large savings in energy use and operational energy bills. These credit requirements are directly tied to the benefits of efficient, low-cost operations.

  • USGBC

    Excerpted from LEED 2009 for New Construction and Major Renovations

    EA Prerequisite 2: Minimum energy performance

    Required

    Intent

    To establish the minimum level of energy efficiency for the proposed building and systems to reduce environmental and economic impacts associated with excessive energy use.

    Requirements

    Option 1. Whole building energy simulation

    Demonstrate a 10% improvement in the proposed building performance rating for new buildings, or a 5% improvement in the proposed building performance rating for major renovations to existing buildings, compared with the baseline building performanceBaseline building performance is the annual energy cost for a building design, used as a baseline for comparison with above-standard design. rating.

    Calculate the baseline building performance rating according to the building performance rating method in Appendix G of ANSI/ASHRAE/IESNA Standard 90.1-2007 (with errata but without addenda1) using a computer simulation model for the whole building project. Projects outside the U.S. may use a USGBC approved equivalent standard2.

    Appendix G of Standard 90.1-2007 requires that the energy analysis done for the building performance rating method include all energy costs associated with the building project. To achieve points using this credit, the proposed design must meet the following criteria:

    • Comply with the mandatory provisions (Sections 5.4, 6.4, 7.4, 8.4, 9.4 and 10.4) in Standard 90.1-2007 (with errata but without addenda1) or USGBC approved equivalent.
    • Inclusion of all the energy costs within and associated with the building project.
    • Compare against a baseline building that complies with Appendix G of Standard 90.1-2007 (with errata but without addenda1) or USGBC approved equivalent. The default process energy cost is 25% of the total energy cost for the baseline building. If the building’s process energy cost is less than 25% of the baseline building energy cost, the LEED submittal must include documentation substantiating that process energy inputs are appropriate.

    For the purpose of this analysis, process energy is considered to include, but is not limited to, office and general miscellaneous equipment, computers, elevators and escalators,kitchen cooking and refrigeration, laundry washing and drying, lighting exempt from the lighting power allowance (e.g., lighting integral to medical equipment) and other (e.g., waterfall pumps).

    Regulated (non-process) energy includes lighting (for the interior, parking garage, surface parking, façade, or building grounds, etc. except as noted above), heating, ventilation and air conditioning (HVAC) (for space heating, space cooling, fans, pumps, toilet exhaust, parking garage ventilation, kitchen hood exhaust, etc.), and service water heating for domestic or space heating purposes.

    Process loads must be identical for both the baseline building performance rating and the proposed building performance rating. However, project teams may follow the exceptional calculation method (ANSI/ASHRAE/IESNA Standard 90.1-2007 G2.5) or USGBC approved equivalent to document measures that reduce process loads. Documentation of process load energy savings must include a list of the assumptions made for both the base and the proposed design, and theoretical or empirical information supporting these assumptions.

    Projects in California may use Title 24-2005, Part 6 in place of ANSI/ASHRAE/IESNA Standard 90.1-2007 for Option 1.

    OR

    Option 2. Prescriptive compliance path: ASHRAE Advanced Energy Design Guide

    Comply with the prescriptive measures of the ASHRAE Advanced Energy Design Guide appropriate to the project scope, outlined below. Project teams must comply with all applicable criteria as established in the Advanced Energy Design Guide for the climate zoneOne of five climatically distinct areas, defined by long-term weather conditions which affect the heating and cooling loads in buildings. The zones were determined according to the 45-year average (1931-1975) of the annual heating and cooling degree-days (base 65 degrees Fahrenheit). An individual building was assigned to a climate zone according to the 45-year average annual degree-days for its National Oceanic and Atmospheric Administration (NOAA) Division. in which the building is located. Projects outside the U.S. may use ASHRAE/ASHRAE/IESNA Standard 90.1-2007 Appendices B and D to determine the appropriate climate zone.

    Path 1. ASHRAE Advanced Energy Design Guide for Small Office Buildings 2004

    The building must meet the following requirements:

    • Less than 20,000 square feet (1,800 square meters).
    • Office occupancy.
    Path 2. ASHRAE Advanced Energy Design Guide for Small Retail Buildings 2006

    The building must meet the following requirements:

    • Less than 20,000 square feet (1,800 square meters).
    • Retail occupancy.
    Path 3. ASHRAE Advanced Energy Design Guide for Small Warehouses and Self Storage Buildings 2008

    The building must meet the following requirements:

    • Less than 50,000 square feet (4,600 square meters).
    • Warehouse or self-storage occupancy.

    OR

    Option 3. Prescriptive compliance path: Advanced Buildings™ Core Performance™ Guide

    Comply with the prescriptive measures identified in the Advanced Buildings™ Core Performance™ Guide developed by the New Buildings Institute. The building must meet the following requirements:

    • Less than 100,000 square feet (9,300 square meters).
    • Comply with Section 1: Design Process Strategies, and Section 2: Core Performance Requirements.
    • Health care, warehouse and laboratory projects are ineligible for this path.

    Projects outside the U.S. may use ASHRAE/ASHRAE/IESNA Standard 90.1-2007 Appendices B and D to determine the appropriate climate zone.

    1Project teams wishing to use ASHRAE approved addenda for the purposes of this prerequisite may do so at their discretion. Addenda must be applied consistently across all LEED credits.

    2 Projects outside the U.S. may use an alternative standard to ANSI/ASHRAE/IESNA Standard 90.1-2007 if it is approved by USGBC as an equivalent standard using the process identified in the LEED 2009 Green Building Design and Construction Global ACP Reference Guide Supplement.

    Potential Technologies & Strategies

    Design the building envelope and systems to meet baseline requirements. Use a computer simulation model to assess the energy performance and identify the most cost-effective energy efficiency measures. Quantify energy performance compared with a baseline building.

    If local code has demonstrated quantitative and textual equivalence following, at a minimum, the U.S. Department of Energy (DOE) standard process for commercial energy code determination, then the results of that analysis may be used to correlate local code performance with ANSI/ASHRAE/IESNA Standard 90.1-2007. Details on the DOE process for commercial energy code determination can be found at http://www.energycodes.gov/implement/
    determinations_com.stm.

    FOOTNOTES

    1 Project teams wishing to use ASHRAE approved addenda for the purposes of this prerequisite may do so at their discretion. Addenda must be applied consistently across all LEED credits.

    2 Projects outside the U.S. may use an alternative standard to ANSI/ASHRAE/IESNA Standard 90.1‐2007 if it is approved by USGBC as an equivalent standard using the process located at www.usgbc.org/leedisglobal

Organizations

Database of State Incentives for Renewables and Efficiency (DSIRE)

This database shows state-by-state incentives for energy efficiency, renewable energy, and other green building measures. Included in this database are incentives on demand control ventilation, ERVs, and HRVs.


New York State Energy Research and Development Authority (NYSERDA)

Useful web resource with information on local/regional incentives for energy-efficiency programs.


American Council for an Energy-Efficient Economy

ACEEE is a nonprofit organization dedicated to advancing energy efficiency through technical and policy assessments; advising policymakers and program managers; collaborating with businesses, public interest groups, and other organizations; and providing education and outreach through conferences, workshops, and publications. 


New Buildings Institute

The New Buildings Institute is a nonprofit, public-benefits corporation dedicated to making buildings better for people and the environment. Its mission is to promote energy efficiency in buildings through technology research, guidelines, and codes.


U.S. Department of Energy, Building Energy Codes Program

The Building Energy Codes program provides comprehensive resources for states and code users, including news, compliance software, code comparisons, and the Status of State Energy Codes database. The database includes state energy contacts, code status, code history, DOE grants awarded, and construction data. The program is also updating the COMcheck-EZ compliance tool to include ANSI/ASHRAE/IESNA 90.1–2007. This compliance tool includes the prescriptive path and trade-off compliance methods. The software generates appropriate compliance forms as well. 


Rensselaer Polytechnic Institute: Daylighting Resources

Research center at RPI provides access to a wide range of  daylighting resources, case studies, design tools, reports, publications and more.


IBPSA

International association of energy modelers with various national and local chapters. 


Architecture 2030

Non-profit organization aiming at design community to increase collaboration for designing energy efficient buildings.


Low Impact Hydropower Institute

The Low Impact Hydropower Institute is a non-profit organization and certification body that establishes criteria against which to judge the environmental impacts of hydropower projects in the United States.


U.S. Department of Energy Building Technologies Program

The Building Technologies Program (BTP) provides resources for commercial and residential building components, energy modeling tools, building energy codes, and appliance standards including the Buildings Energy Data Book, High Performance Buildings Database and Software Tools Directory.

Web Tools

Energy Analysis Tools

This website discusses the step-by-step process for energy modeling.


Advanced Buildings Technologies and Practices

This online resource, supported by Natural Resources Canada, presents energy-efficient technologies, strategies for commercial buildings, and pertinent case studies.


U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy

This website is a comprehensive resource for U.S. Department of Energy information on energy efficiency and renewable energy and provides access to energy links and downloadable documents. 


U.S. EPA, Combined Heat and Power Partnership

Information on cogenerationThe simultaneous production of electric and thermal energy in on-site, distributed energy systems; typically, waste heat from the electricity generation process is recovered and used to heat, cool, or dehumidify building space. Neither generation of electricity without use of the byproduct heat, nor waste-heat recovery from processes other than electricity generation is included in the definition of cogeneration., also called combined heat and power, is available from EPA through the CHPCombined heat and power (CHP), or cogeneration, generates both electrical power and thermal energy from a single fuel source. Partnership. The CHP Partnership is a voluntary program seeking to reduce the environmental impact of power generation by promoting the use of CHP. The Partnership works closely with energy users, the CHP industry, state and local governments, and other clean energy stakeholders to facilitate the development of new projects and to promote their environmental and economic benefits. 


Advanced Energy Design Guides

Free download of AHSRAE energy savings guide, use for Option 2.


Lawrence Berkeley Lab: Building Technologies Department

Research warehouse for strategies and case studies of energy efficiency in buildings.


Efficient Windows Collaborative

An online window selection tool with performance characteristics.


Whole Building Design Guide (WBDG)

This website lays out design process for developing an energy efficient building.


AIA Sustainability 2030 Toolkit

This website discusses ways to improve design for lower energy demand as they relate to the AIA 2030 challenge.


Windows for High-Performance Commercial Buildings

This website includes discussion of design issues, materials and assemblies, window design decisions and case studies. 


California Integrated Waste Management Board: Environmental and Economic Assessment Tools

This site lists multiple web-based and downloadable tools that can be used for energy analyses.


DEER: Database for Energy Efficient Resource

This database is maintainted by the California Energy Commission and lists resources related to energy use and efficiency. 


Energy Design Resources - CA

Energy design tools are available to be used for free online or available to download.


Building Materials Property Table

This website lists performance characteristics for various envelope materials. 


One Building

This is an online forum of discussion for energy efficiency, computer model software users.


EPA’s Target Finder

Target Finder is a goal-setting tool that informs your design team about their project’s energy performance as compared to a national database of projects compiled by the EPA.


Building Energy Software Tools Directory

This directory provides information on 406 building software tools for evaluating energy efficiency, renewable energy, and sustainability in buildings.


EnergyPlus Format Weather Data Resources

Weather data for more than 2100 locations are available in EnergyPlus weather format.


DOE-2 Format Weather Data Resources

Weather data for U.S. and Non-U.S. locations in BIN format.


BEMbook – Building Energy Modeling Book

A web-based, free content project by IBPSA-USA to develop an online compendium of the domain of Building Energy Modeling (BEM). The intention is to delineate a cohesive body of knowledge for building energy modeling.

Technical Guides

Advanced Buildings Core Performance Guide

A guide for achieving energy efficiency in new commercial buildings, referenced in the LEED energy credits.


ENERGY STAR Building Upgrade Manual

This manual is a strategic guide for planning and implementing energy-saving building upgrades. It provides general methods for reviewing and adjusting system control settings, plus procedures for testing and correcting calibration and operation of system components such as sensors, actuators, and controlled devices.


Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 – Design & Construction

This document is USGBC’s second (v2.0) major release of guidance for district or campus thermal energy in LEED, and is a unified set of guidance comprising the following an update to the original Version 1.0 guidance released May 2008 for LEED v2.x and the initial release of formal guidance for LEED v2009.


COMNET Commercial Buildings Energy Modeling Guidelines and Procedures

This manual offers guidance to building energy modelers, ensuring technically rigorous and credible assessment of energy performance of commercial and multifamily residential buildings. It provides a streamlined process that can be used with various existing modeling software and systems, across a range of programs.


2009 ASHRAE Handbook of Fundamentals, Chapter 19

Chapter 19 is titled, “Energy Estimating and Modeling Methods”. The chapter discusses methods for estimating energy use for two purposes: modeling for building and HVAC system design and associated design optimization (forward modeling), and modeling energy use of existing buildings for establishing baselines and calculating retrofit savings (data-driven modeling).


Treatment of Distric or Campus Thermal Energy in LEED v2 and LEED 2009 (Updated August 13, 2010)

Required reference document for DES systems in LEED energy credits.

Publications

ANSI/ASHRAE/IESNA Standard 90.1–2007 User’s Manual (ASHRAE).

ASHRAE writes standards for the purpose of establishing consensus for: 1) methods of test for use in commerce and 2) performance criteria for use as facilitators with which to guide the industry.


Energy Information Administration

Energy statistics from the U.S. government.


New Buildings Institute— Advanced Lighting Guidelines: 2003 Edition

This guide includes instructional graphics and superior lighting design solutions for varying types of buildings and spaces, from private offices to big box retail stores.


Building Energy Performance News

This website offers information on energy efficiency in buildings, highlighting success stories, breakthrough technology, and policy updates.


GreenSource magazine

Bimonthly publication on case studies and new technologies for energy efficiency in commercial buildings. 


AIA Local Leaders in Sustainability: Green Incentives

AIA publication highlighting local and state green building incentives.


Federal Research and Devlopment Agenda for Net-Zero Energy, High-Performance Green Buildings

2008 guidelines and performance goals from the National Science and Technology Council.


Energy Design Resources (EDR) Simulation Guidebooks

Information about energy-efficient building practices available in EDR's Design Briefs, Design Guidelines, Case Studies, and Technology Overviews.

Software Tools

Building Energy Software Tools Directory

DOE tools for whole building analyses, including energy simulation, load calculation, renewable energy, retrofit analysis and green buildings tools.


Building and Fire Research Laboratory

This is a computer program that predicts the one-dimensional transfer of heat and moisture.


DesignBuilder and EnergyPlus

DesignBuilder is a Graphical User Interface to EnergyPlus. DesignBuilder is a complete 3-D graphical design modeling and energy use simulation program providing information on building energy consumption, CO2Carbon dioxide emissions, occupant comfort, daylighting effects, ASHRAE 90.1 and LEED compliance, and more.


Integrated Environmental Solutions – Virtual Environment Pro / Apache

IES VE Pro is an integrated computing environment encompassing a wide range of tasks in building design including model building, energy/carbon, solar, light, HVAC, climate, airflow, value/cost and egress.

Advanced Energy Design Guide Checklist

Option 2: Prescriptive Compliance Path

Use this checklist of prescriptive requirements (with sample filled out) to have an at-a-glance picture of AEDG requirements for Option 2, and how your project is meeting them.

Advanced Buildings Core Performance Guide (CPG) Checklist

Option 3

This spreadsheet lists all the requirements for meeting EAp2 – Option 3 and and EAc1 – Option 3. You can review the requirements, assign responsible parties and track status of each requirement through design and construction.

Energy Simulation Narrative

Option 1

Sometimes the energy simulation software being used to demonstrate compliance with Option 1 doesn't allow you to simulate key aspects of the design. In this situation you'll need to write a short sample narrative, as in these examples, describing the situation and how it was handled.

Equipment and Product Cut Sheets

All Options

In your supporting documentation, include spec sheets of equipment described in the Option 1 energy model or Options 2–3 prescriptive paths.

PRM Table

Option 1

This is a sample building energy performance and cost summary using the Performance Rating Method (PRM). Electricity and natural gas use should be broken down by end uses including space heating, space cooling, lights, task lights, ventilation fans, pumps, and domestic hot water, at the least.

Tariff Charges

Option 1

Option 1 calculates savings in annual energy cost, but utility prices may vary over the course of a year. This sample demonstrates how to document varying electricity tariffs.

Modeled Energy Reductions

Option 1

This graph, for an office building design, shows how five overall strategies were implemented to realize energy savings of 30% below an ASHRAE baseline. (From modeling conducted by Synergy Engineering, PLLC.)

U.S. Climate Zones

All Options

The climate zones shown on this Department of Energy map are relevant to all options for this credit.

Appendix G Fan Power Calculator

Option 1

This spreadsheet, provided here by 7group, can be used to calculate the fan volume and fan power for Appendix G models submitted for EAp2/EAc1.  Tabs are included to cover both ASHRAE 90.1-2004 and 90.1-2007 Appendix G methodologies.

LEED Online Forms: NC-2009 EA

The following links take you to the public, informational versions of the dynamic LEED Online forms for each NC-2009 EA credit. You'll need to fill out the live versions of these forms on LEED Online for each credit you hope to earn.

Version 4 forms (newest):

Version 3 forms:

These links are posted by LEEDuser with USGBC's permission. USGBC has certain usage restrictsions for these forms; for more information, visit LEED Online and click "Sample Forms Download."

Design Submittal

PencilDocumentation for this credit can be part of a Design Phase submittal.

2378 Comments

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April Brown Projects Manager Institute for the Built Environment
Sep 18 2014
LEEDuser Expert
502 Thumbs Up

Equipment Capacity for Design and Baseline Case

Hi Marcus etEvapotranspiration (ET) is the loss of water by evaporation from the soil and by transpiration from plants. It is expressed in millimeters per unit of time. al.,

I received a question from one of our project energy modelers that I cannot answer -

Recently we have been receiving a new comment on EAp2 that states
“The HVAC equipment capacities cannot be autosized in the Proposed model.”

This comment brings up the following concerns. Our actual design documents include engineering of the building, safety factors, owner desired extra capacities, & good engineering practices for operation & functionality. If we are to put in the true design capacities (which are peak capacities plus safety factors not average operating conditions) but allow the baseline to auto calculate, we are never going to show energy savings as the baseline has none of the previously mentioned included. The baseline is bare bones and as minimal as one can get. Are we allowed to also put in the design capacities in for the baseline? For example, in past experience, the baseline requires more airflow because the equipment is a little less efficient and the envelope typically has a lower R value & better glazing than the proposed. However, if we have to hard input our design Peak airflows but allow the baseline to calculate airflows there will be skewed results. The reason I say this is that in general an interior room may require 50 CFM to meet its load. However, we know that diffusersIn an HVAC context, diffusers disperse heating, cooling, or ventilation air as it enters a room, ideally preventing uncomfortable direct currents and in many cases, reducing energy costs and improving indoor air quality (IAQ). In light fixtures, diffusers filter and disperse light. need a minimum of 75-100 CFM for the air to actually reach the occupant and effectively cool the space. Therefore, our design would show 100 CFM and the baseline model would calculate 50 CFM. This does not seem like a fair and true comparison.

Can you offer insight and direction for how to adjust our model to address the reviewer concerns while still showing energy cost savings and reflecting our actual design conditions?

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Matt Scott Engineer, N.E. Fisher & Associates, Inc. Sep 18 2014 Guest 241 Thumbs Up

My two cents... Appendix G is pretty clear that if you have completed design documents, you cannot auto-size the proposed case, and you must model the HVAC system "as designed" including the scheduled capacities. Remember, the baseline capacities are to be over-sized by 15% for cooling and 25% for heating, so that should help make up for a little "over-engineering" on the proposed case.

You should still be able to squeeze some points out even with these restrictions. I've found the baseline systems pretty much always have lower airflows, but in the end the proposed systems are usually still more efficient and use less overall energy than the baseline theoretical systems.

Safety factors and "good engineering practice" enter a grey area of violating the energy code and engineering in extra capacity isn't really "green" and being green is the whole point; getting the certification is just a bonus.

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Marcus Sheffer LEED Fellow, 7group Sep 18 2014 LEEDuser Expert 42317 Thumbs Up

Agreed. If you oversize the Proposed systems to any significant degree you should pay a penalty. The software will calculate peaks and average based on the actual loads so you are not really comparing average to peak. You enter the full capacity and the software automatically matches the capacity needed to the loads in both models.

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Khaled Fouda Sep 18 2014 LEEDuser Member 14 Thumbs Up

This issue brings a question to my mind. The multifamily building that I am working at right now has some unconditioned (no cooling) spaces and according to Appx.G I should model these spaces identically with the baseline. I am wondering if I will ever receive a comment from the reviewer about some proposed systems being (auto-sized) and being (15% over-sized).

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Marcus Sheffer LEED Fellow, 7group Sep 18 2014 LEEDuser Expert 42317 Thumbs Up

The reviewer will check the proposed system capacities against the information in the mechanical schedules to ensure that the proposed is modeled as designed. If they are only slightly off you should not get a comment however.

There are times when auto-sizing proposed systems is appropriate. Like when you have to model a space that does not have a mechanical design identically to the baseline system.

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LEEDme STRATEGIE D'IMPRESA
Sep 16 2014
LEEDuser Member
66 Thumbs Up

Radiant tube

A radiant tube gas can be associated with the table 6.8.1E ASHRAE 2007?

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Marcus Sheffer LEED Fellow, 7group Sep 17 2014 LEEDuser Expert 42317 Thumbs Up

Gas radiant heaters are not covered in the 6.8.1 Tables. So there is no minimum efficiency requirement.

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HOUCINE TLEMSANI Mechanical Designer MEP Engineering Solutions, Inc
Sep 11 2014
LEEDuser Member
296 Thumbs Up

kitchen hoods

Hi,
I am working on a dining facility where we have two makeup air units serving the kitchen hoods. The units in the proposed case are equipped with chilled water coils served with the building air cooled chiller to tamper the air to 80 degree F. the units are considered as process and are supposed to be modeled identical in the proposed and the baseline case. Since the building chiller is a high performance magnetic chiller serving the whole building what is the baseline piece of equipment that needs to be modeled to serve the makeup units since the baseline system is type 3 dx packaged units.
Is it an air cooled chiller with ASHRAE 90.1 performance and sized for the coils capacity?

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HOUCINE TLEMSANI Mechanical Designer, MEP Engineering Solutions, Inc Sep 17 2014 LEEDuser Member 296 Thumbs Up

Any guidance would be appreciated. Thanks.

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Victoria Watson Sep 17 2014 Guest 98 Thumbs Up

Hi Houcine,
One way of thinking about this (I am be wrong) is that perhaps the makeup units are not classed as process energy if they have chilled water coils as they are conditioning the space. However the outside ventilation rates should be the same in both building so the baseline building would also need to makeup this air. If the baseline system is type 3 DX packaged units, then this serves the space but with the outside air rate to match the proposed building (E.g. there will be a constant outside air during times the makeup unit is in operating in the proposed at that rate).

Anyone have any other thoughts? I have come across similar tricky situations with makeup air in buildings.

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HOUCINE TLEMSANI Mechanical Designer, MEP Engineering Solutions, Inc Sep 19 2014 LEEDuser Member 296 Thumbs Up

Thanks Victoria
The kitchen makeup units are serving 80% of the hood required makeup the rest is coming from the building system and are not really conditioning the space. The only reason the air is tempered to 80F is for the cooks safety purpose and RFP requirement. All the hoods ventilation system is for kitchen heat and smoke removal. Therefore I believe that it is process, (correct me if I am wrong).
My question is that if it is process how will it be modeled in the base line and what type of equipment will be modeled for the chilled water coils. Since the base line model does not have a chilled water system.
I guess the only way is to compare it to a chiller with ASHRAE 90.1 performance and claim savings.
Anyone had this situation?

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E H Sustainability Architect
Sep 10 2014
LEEDuser Member
3030 Thumbs Up

Baseline system(s) for mixed use building?

We have a project that consists of 1 level of retail, 7 levels of above grade parking, 8 levels of commercial office space, and 16 levels of residential (apartment) space. Based on overall building square footage, the baseline energy model would utilize System 7 – VAVVariable Air Volume (VAV) is an HVAC conservation feature that supplies varying quantities of conditioned (heated or cooled) air to different parts of a building according to the heating and cooling needs of those specific areas. with Reheat. However, under normal circumstances, if the building was 100% residential the baseline would use System 1- PTAC. It could also be argued that because the office space is an 8am-5pm occupancy and the residential space is 24/7 that exception G3.1.1.b could be used to model each residential unit as an individual thermal zone with a packaged rooftop unit. How can we determine how the baseline should be set up? Any guidance would be appreciated. Thanks.

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Marcus Sheffer LEED Fellow, 7group Sep 10 2014 LEEDuser Expert 42317 Thumbs Up

Assuming the parking is unconditioned it does not enter into the equation at all. The residential is a system 1 and is predominant. Exception "a" then applies since the other uses are nonresidential. The 8 office floors and 1 retail floor are still greater than 5 floors so they are a system 7. Not sure if the retail would meet any of the other exceptions.

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E H Sustainability Architect Sep 17 2014 LEEDuser Member 3030 Thumbs Up

Thanks, Marcus!

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Vassil Vassilev Manager Termoservice OOD
Sep 10 2014
LEEDuser Member
3 Thumbs Up

Modeling a manufacturing building

Hi,
I'm modeling a manufacturing plant. The issues I'm looking for advises are related to modeling the manufacturing process and specifically:
Cooling. There are several molding presses, which are cooled with cold water via their cooling shell (closed loop). The cold water is provided by two air cooled chillers having the total capacity of 128 tons. The chillers are designed to operate with an integrated free cooling package whenever the weather allows it.
The questions are:
1. How could this cooling system be assigned to any of the app. G3.1 table. The building as a whole (area, floors..) belongs to System 5, but I'm not sure how to actually proceed - may be exceptional calculation method?
2. In case the cooling system should be identical for Proposed and Baseline (industrial process), should the free cooling option also to be applied to the Baseline model or there should be just an air cooled chiller. The presumption is that the Proposed building is investing more for increasing the energy efficiency.
Thanks.

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Marcus Sheffer LEED Fellow, 7group Sep 10 2014 LEEDuser Expert 42317 Thumbs Up

This cooling is a process load.

1. Table G3.1.1A does not apply. You must model this process identically in the Baseline unless you are trying to claim savings. If you are trying to claim savings then follow the exceptional calculation method.

2. You would need to justify any savings association with the free cooling as an exceptional calculation. A narrative should describe all Baseline and Proposed case assumptions included for this measure as well as the calculation methodology used to determine the projected savings. The narrative and energy savings should be reported separately from the other efficiency measures in Section 1.7 - Table EAp2-7. The Baseline case description should verify that the efficiency measure is not standard practice for a similar newly constructed facility. Baseline justification must be provided by referencing a recently published document (published within five years of the project registration date), utility program that incentivizes the equipment installed, or by documenting systems used to perform the same function in other newly constructed facilities (three facilities built within the past five years of the project registration date). Savings associated with the proposed case measure should also be justified with published or monitored data.

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Vassil Vassilev Manager, Termoservice OOD Sep 10 2014 LEEDuser Member 3 Thumbs Up

Markus, thanks again for your answer.
For this particular project I've not been provided with any data of the manufacturing equipment (molding press), so I can't make any exceptional calculation for it. In one previous project I've been receiving such data and when I've made there the exceptional calculation as explained by you, I've received the reviewr's approval.
But here I'm asking only about the way of organizing the cold water supply.
In principle there are standart cooling options - air cooled chiller or water cooled with a cooling tower. In this case it was selected one of these typical solution, but with one extra - free cooling option.
If I make an exceptional calculation method just for this cooling part by comparing a standart air cooled chiller with an air cooled with free cooling, will this be accepted?
If not, then all process loads will be identical. So , again my question is just for the cooling.
Thanks

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Marcus Sheffer LEED Fellow, 7group Sep 10 2014 LEEDuser Expert 42317 Thumbs Up

If it were me I would tell my client that I cannot complete the model without data on the equipment.

If you try to claim savings for a component of a system but you do not have any real basis for that system I would certainly not accept it. The Baseline must be well defined and in this case you are making a big assumption.

If you make it identical it should be accepted.

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Vassil Vassilev Manager, Termoservice OOD Sep 10 2014 LEEDuser Member 3 Thumbs Up

Thanks for the reply, Markus.
I have the data of the manufacturing equipment, but the client didn't provide data that he has purchased equipment which is different from the standart practice regardless how many time I've mentioned about it. Even quoting my previous project where such approach was approved.

The cooling option was reported to me as a free coise, which are to be made by client's specialists, base on the climate zoneOne of five climatically distinct areas, defined by long-term weather conditions which affect the heating and cooling loads in buildings. The zones were determined according to the 45-year average (1931-1975) of the annual heating and cooling degree-days (base 65 degrees Fahrenheit). An individual building was assigned to a climate zone according to the 45-year average annual degree-days for its National Oceanic and Atmospheric Administration (NOAA) Division. analysis. So their final decision was to an air cooled chiller with free cooling pacage.
Modeling everything identical is not a problem, I've been just thinking whether it desrves a trial for cooling exceptional calculation, but as you say that it will not be accepted, then better save time in this issue,
Thanks

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Marcus Sheffer LEED Fellow, 7group Sep 10 2014 LEEDuser Expert 42317 Thumbs Up

So again if you can define the baseline within an exceptional calculation method you can certainly pursue it. You will need to make the case for a baseline. Perhaps the manufacturer can help you with that instead of the client.

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Khaled Fouda
Sep 09 2014
LEEDuser Member
14 Thumbs Up

Table 1.4

I have couple of questions about filling table 1.4.7:

1- Table 1.4.7A asks for the total cooling capacity, I use HAP 4.6 and the cooling capacities are calculated according to ASHRAE 90.1. Shall I run the simulation and then get the output results?

2- Table 1.4.7B, I am not sure of some system inputs yet in the proposed model, so I use ASHRAE 90.1 and let the software calculate. Shall I fill the table with the software results? Will it still be accepted although it is mentioned that all inputs should be consistent with the Proposed energy model andthe mechanical drawings and equipment schedules submitted to LEED ONLINE.

Note: HAP output cooling capacities are away smaller than my actual equipments capacities used in the Proposed model. Will I receive a comment on this?

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Marcus Sheffer LEED Fellow, 7group Sep 09 2014 LEEDuser Expert 42317 Thumbs Up

1. Yes, the cooling capacity HAP calculated would be the input.
2.You should be virtually certain about the inputs for your proposed model before you do the final model for LEED. The software should not auto-size anything. Whether it will be questioned depends on the degree to which the input variable is off and which particular input is in question. If the system capacity is slightly off it should be fine. If the fan power is way off it will be questioned.
Note. If they are way smaller then it will probably be questioned.

Always model the Proposed as designed. Do not auto-size anything.

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Agata Mozer GO4IT SP Z OO SP K
Sep 09 2014
LEEDuser Member
128 Thumbs Up

reference systems for a warehouse building

We are working on a warehouse project with small attached administration building. I have a question regarding reference systems for this project. The warehouse building has floor heating and exhaust fans (outdoor air is supplied naturally via loading gates; there's no cooling system). Administration building (which is smaller than 1900sqm) has a separate HVAC system (AHUs and VRF system).
1. According to table G3.1.1A the reference system for the warehouse (predominant condition) should be system 7. However there are no supply fans in the proposed case so I'm not sure if we should include them in the reference model?
2. Since the administration office is smaller than 1900sqm exception a) of section G3.1.1 doesn't apply. In that case since there are different occupancy and loads schedules than in the warehouse we assumed that exception b) should be implemented and system 4 should be modeled (electric heating in the administartion building), is that correct?

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Marcus Sheffer LEED Fellow, 7group Sep 09 2014 LEEDuser Expert 42317 Thumbs Up

To avoid some of the "rules" around heating only systems I would apply Addendum dn and model the warehouse as a system 9 or 10. Then apply exception b to the office.

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Agata Mozer GO4IT SP Z OO SP K Sep 11 2014 LEEDuser Member 128 Thumbs Up

Thank you Marcus. I checked Addendum dn and as you mentioned system 11 would be most appropriate for the warehouse. If I understood it well, this system should be modeled as packaged rooftop with warm air furnance? And I have one more question regarding fans in this reference system:
1. In the proposed case there are only exhaust fans (outdoor air is supplied naturally via loading gates). Should the fans in the reference be simulated identically as in the proposed case or should the energy usage of the reference fans be calculated based on ASHRAE guidelines (power of fans calculated based on pressure drop only for exhaust airflow control devices)?

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Marcus Sheffer LEED Fellow, 7group Sep 11 2014 LEEDuser Expert 42317 Thumbs Up

The addendum mislabels the system numbers. If you look in 90.1-2010 they are labeled system 9 and 10.

ASHRAE 90.1-2010 defines System Type 9 as a constant volume warm air furnace, gas fired, with no cooling. System Type 10 is defined as a constant volume warm air furnace, electric resistance. The Baseline efficiencies for these systems should be determined based on ASHRAE 90.1-2007 Table 6.8.1E.

Baseline system air flow rates for System Types 9 and 10 shall be determined based on the temperature differential between 105 degrees F and the design space heating temperature setpoint, the minimum outdoor air flow rate, or the air flow rate required to meet applicable code or accreditation standards, whichever is greater. The fan power for System Type 9 or 10 should be 0.3 Watts per cfm of Baseline heating supply airflow.

Should the system include a fan to provide non-mechanical cooling (i.e. increased fan air flow rates set to operate once indoor or outdoor temperature exceed a certain temperature, or direct or indirect evaporative cooling), the Baseline model should also include a separate fan to provide non-mechanical cooling, sized and controlled the same as the Proposed design. For non-mechanical cooling fans, the Baseline fan power should be modeled as 0.054 Watts per cfm of non-mechanical cooling airflow.

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Victoria Watson
Sep 03 2014
Guest
98 Thumbs Up

Continuous insulation - Interrupted by slab vs truly continuous

Hi,

I am modeling a masonry building. There have been discussions about whether the insulation should go on the outside (therefore truly continuous) with an extra veneer to finish or on the inside (interrupted only by the slabs on each floor). It does not look like ASHRAE 90.1 deals with this situation very well (e.g gives much guidance). Using Appendix A, Table A3.1A gives U Values for masonry walls with continuous insulation Uninterrupted by Framing. Neither of the cases are interrupted by framing however is it fair to use the same table in both scenarios for the energy model?
Thanks
Victoria

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Francesco Passerini engineer, leedme.it Sep 04 2014 Guest 1030 Thumbs Up

I think that the insulation is better on the outside side for three reasons:
1. the thermal bridges are reduced
2. condensation problems inside the wall are less probable
3. you have more thermal inertia for the indoor space.
I don't know exactly how ASHRAE is considering the issue. I'm looking forward to reading other comments.
Regards

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Marcus Sheffer LEED Fellow, 7group Sep 05 2014 LEEDuser Expert 42317 Thumbs Up

I agree with Francesco. Continuous insulation and thermal mass are the important considerations.

As far as Appendix A make sure you read the assumed layers that are used to derive the values in the tables. So in this case read all of A3.1 since it describes the assumptions that went into the numbers in the tables. If your situation varies you need to make reasonable adjustments to derive your U-factor.

In one scenario you have continuous insulation and the other you do not. So if the basis of the table is continuous insulation then you would need to make adjustments to the overall assembly U-factor.

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Chris Hammett Mechanical Designer Turpin & Rattan Engineering, Inc.
Aug 28 2014
Guest

Energy Modeling for Casino

Hello. I am working on the energy model for a casino/hotel/nightclub. I have been contracted only to develop the model, no input in regards to design. I have built the entire model in Energy Pro with the exception of the interior and exterior lighting. The energy savings are well above baseline. However, I have begun inputing the installed lighting and the power is off the chart. I am seeing conflicting interpretations on how to treat lighting. Some sources say that if it is superfluous to the general lighting for the space, consider it process. I understand that per ASHRAE 90.1, Casino gaming floor lighting is treated as process. I do not have any technical or official resources that say that you can declare a portion of the lighting for nightclub as decorative/process. Some of the nightclub spaces are 7 watts per square foot. Can a portion of this lighting be considered process or task or something?

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Marcus Sheffer LEED Fellow, 7group Aug 28 2014 LEEDuser Expert 42317 Thumbs Up

The Exceptions to Section 9.2.2.3 are the ones that are considered process.

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Chris Hammett Mechanical Designer, Turpin & Rattan Engineering, Inc. Aug 28 2014 Guest

Marcus, thank you for your quick reply. In a few instances below you have suggested that you can claim lighting is decorative if you remove that lighting and the remaining lighting meets the lighting design requirements. That is what I am getting at here. Other questions also speak of decorative lighting and decorative lighting allowance. Where can I find information on decorative lighting allowance in LEED or ASHRAE? Much of the lighting that I am discussing is separately circuited, it just does not fit nicely into the exceptions under 9.2.2.3, I would say it is kind of a grey area.

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Marcus Sheffer LEED Fellow, 7group Aug 28 2014 LEEDuser Expert 42317 Thumbs Up

If it does not meet a specific exception then you have to make the case that the lighting in question is over and above what is needed for illumination as a means to claim it as process lighting.

You could also just tell the client that 7 W/sf is ridiculous, unnecessary and highly wasteful and in my opinion means it should not be allowed to be called a green building. For me this kind of thing comes down to doing the right thing. Is LEED all about trying to find an exception to allow wasteful practice? Even though you are not doing the design (we never do the design and make recommendations using the energy model all the time, in fact that is the point of energy modeling!), you could certainly talk to the client about how the lighting kills all the savings and encourage them to seek ways to reduce it. Maybe it can get down to 5 W/sf! How about being the first all LED Casino?

Sorry for the rant but doing a green building is just not about seeking exceptions to allow for poor energy performance.

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Matt Scott Engineer N.E. Fisher & Associates, Inc.
Aug 27 2014
Guest
241 Thumbs Up

Baseline Fan Power Heat Recovery

I have a few questions on baseline fan power taking credit for heat recovery in the proposed building.

1. Say I have heat recovery in my proposed system, but it is not required in my baseline system. Do I or don't I get to take credit for the added proposed fan power by adding the heat recovery device pressure drop to the baseline fan power calc? Table 1.4 Air-Side HVAC says:
•only if modeled in Baseline per G3.1.2.10

2. Say I have an energy recovery unit exhausting 1000 CFM at 0.5" external static and supplying 1200 cfm at 0.3" external static. How do I properly account for the different CFMs and static pressures? Should I just sum the static pressures and only input 1000 CFM at 0.8"?

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Marcus Sheffer LEED Fellow, 7group Aug 28 2014 LEEDuser Expert 42317 Thumbs Up

1. You can only take the heat recovery adjustment if there is heat recovery required in the Baseline. If heat recovery is not required then you do pay a penalty for the added fan power. This makes sense as the extra fan power is a reality of choosing to add heat recovery to the Proposed system.
2. It should be modeled as designed. Have you entered it in the software as designed? Not sure what software you are using and this could be a specific modeling question that may be better to address to a different discussion forum. You should not sum the static pressures.

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Matt Scott Engineer, N.E. Fisher & Associates, Inc. Aug 28 2014 Guest 241 Thumbs Up

1. Understood. I see your point and agree.

2. I'm using HAP. For Heat Recovery it only allows you to input a KW to turn the wheel and its thermal efficiency. One of the ERUs on the job is scheduled as follows:
Supply Fan= 4700 CFM at 0.35" external static pressure, 2.05 BHP
Exhaust Fan= 4000 CFM at 0.6" external static pressure, 1.59 BHP

If I was required by Appendix G to model this heat recovery for a baseline system, how would I determine the allowed baseline fan power in this case?

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Marcus Sheffer LEED Fellow, 7group Aug 28 2014 LEEDuser Expert 42317 Thumbs Up

Do not know HAP real well beyond evaluating the input and output reports we see when doing LEED reviews. A specific "how to model something question" should be directed to HAP support since you pay for it anyway.

This system would not be required to have heat recovery since the cfm is below 5,000.

The baseline fan power is based on the supply air cfm and the result includes the all fans including the exhaust. If required to have heat recovery you also include the heat recovery pressure drop adjustment.

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Matt Scott Engineer, N.E. Fisher & Associates, Inc. Aug 28 2014 Guest 241 Thumbs Up

But in this case what would be the heat recovery pressure drop adjustment? Just the outdoor air component? 4700 CFM at 0.35" static? Is baseline heat recovery assumed to be "ideal" with no additional fan energy and only pressure drop across a wheel?

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Marcus Sheffer LEED Fellow, 7group Aug 28 2014 LEEDuser Expert 42317 Thumbs Up

The pressure drop adjustment is based on the pressure drop across the heat recovery wheel which comes from the manufacturer.

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Omar ElRawy Building Engineer, LEED AP BD+C EA Building Consultants
Aug 26 2014
Guest
495 Thumbs Up

Motor Power

Dear All,
For modelling pumps for my Proposed design, I have a manufacturer's datasheet for a Variable speed pump (Secondary pump) with the following values:

Duty Flow = 209.5 gpm
Duty Head = 50 ft
Motor Size = 5.5 KW
KWa @Design = 3 KW
BHP/pump = 3 KW

while the constant speed pump (primary) have the following values:
Duty Flow = 209.5 gpm
Duty Head = 35 ft
Motor Size = 2.2 KW
KWa @Design = 1.73 KW

Now for calculating the W/gpm, should I use KW@Design/Duty Flow, or Motor Size/Duty Flow?
And, Should I enter the Duty Head to the Energy Model, or leave it auto?

Thanks

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Marcus Sheffer LEED Fellow, 7group Aug 26 2014 LEEDuser Expert 42317 Thumbs Up

Use the KW@Design and duty head. Always model the Proposed as designed (well not always but almost always).

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Jon Clifford LEED-AP BD+C GREENSQUARE ∙ Sustainability ∙ Construction ∙ Specifications
Aug 21 2014
LEEDuser Member
416 Thumbs Up

Parking Garages Abutting Conditioned Space

While we are on the topic of parking garages, I have had projects where a parking garage abutted a conditioned building. Reviewers have treated them differently.

During the review of one project, GBCI reviewers obsessed about the potential for heat transfer from the building to the garage. The reviewer said, “The reviewer has seen several similar situations where the project team has modeled the adjoining facade as adiabatic walls. This is inappropriate. Because the Parking Garage is open to ambient conditions, the adjoining building’s walls should be modeled as exterior walls like the rest of the facade.” In our case, the reviewer’s concern was unwarranted. The garage and the building were completely isolated from one another, with a 3” expansion joint at all slab connections, and the adjoining wall WAS modeled and built as an exterior wall.

On another project, the garage included conditioned elevator lobbies at each floor with no break in the slab between interior and exterior. Insulation was applied the underside of the slab, but the slabs & beams themselves ran continuously through the adjoining wall. Somehow, this raised no concern for the reviewers, but I was never sure that we had modeled heat transfer correctly where the slab passed from indoors to outdoors.

This is a common condition, how should it be modeled?

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Marcus Sheffer LEED Fellow, 7group Aug 21 2014 LEEDuser Expert 42317 Thumbs Up

The parking garage is the same as exterior space. The wall between the conditioned and unconditioned space should be treated as an exterior wall. In terms of the details related to thermal breaks see Table G3.1-5. They must be accounted for in the overall assembly U-valueU-value describes how well a building element conducts heat. It measures the rate of heat transfer through a building element over a given area, under standardized conditions. The greater the U-value, the less efficient the building element is as an insulator. The inverse of (1 divided by) the U-value is the R-value.. Most modeling software does not account for these kinds of thermal breaks so you need to alter the entered U-values and not enter a point calculation. See also 90.1 Appendix A for guidance on accounting for the structure and framing in various construction assemblies.

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Yastimy Jupson Green Building Consultant
Aug 21 2014
Guest

Old HVAC equipment transferred from other site

Hello,

I have a new factory project recently. The owner wants to transferred old HVAC equipment from their old factory to this new factory. Do these old HVAC equipment transferred from other site need to meet ASHRAE 90.1 Mandotary Parts? I know the on-site existing HVAC equipment needn't, but not sure about this case. Also, do I need to compare these old HVAC equipment to ASHRAE required baseline system? or I can use old HVAC equipment for both baseline and proposed case?

Thanks!

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Marcus Sheffer LEED Fellow, 7group Aug 26 2014 LEEDuser Expert 42317 Thumbs Up

The old HVAC equipment used in a new facility would need to comply with the mandatory provisions. For LEED the project needs to comply with the ASHRAE 90.1-2007 mandatory provisions. In this case the mandatory provision for equipment efficiency would need to be met.

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CT G
Aug 20 2014
LEEDuser Member
126 Thumbs Up

Glazing ratio

We are working with a building that has 9 floors, the first 6 floors are for parking, unconditioned naturally ventilated with no glass on the envelope, and the last 3 are conditioned office spaces with a high WWR.

To model the baseline, should we consider the whole façades of the building (6 parking floors + 3 office floors) to calculate the 40%, or just the conditioned height (3 office floors)?
From table G3.1-5 it seems that the whole façade should be used to calculate the WWR: "40% of gross above-grade wall area, whichever is smaller,"

To select the Baseline HVAC system we are considering just 3 floors, as we understand, from Marcus´ comment previously posted, that only conditioned floors count.

Thanks in advance,
Anderson

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Marcus Sheffer LEED Fellow, 7group Aug 20 2014 LEEDuser Expert 42317 Thumbs Up

I will not disagree with myself, at least this time!

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Jean Marais b.i.g. Bechtold DesignBuilder Expert Aug 21 2014 LEEDuser Member 8474 Thumbs Up

- It has been ruled (last I heard) that parking buildings are not LEED certifiable.
- It is said that the building should concider all parts that are needed for it's function...in your case I was thinking that the parking is not for the offices per say and should probably be excluded.
- The WWR rule applies only to surfaces where the proposed design has glazing. You can't put glazing where there isn't any in the proposed design.

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Jon Clifford LEED-AP BD+C, GREENSQUARE ∙ Sustainability ∙ Construction ∙ Specifications Aug 21 2014 LEEDuser Member 416 Thumbs Up

Clarification: On its own, an unconditioned, unoccupied parking garage is not eligible for LEED certification. However, a parking garage attached to a conditioned building and within the LEED project boundary may be certified as part of that project. In this case, all costs, materials, and activities associated with the garage must be taken into account for all credits & prerequisites.

That said, the window-to-wall ratio only applies to walls that enclose conditioned space, so the walls of an unconditioned garage must be excluded from this calculation.

On the other hand, for the energy models, one must include lighting, mechanical ventilation, & other loads associated with the garage, even though it is unconditioned.

Is that right, Marcus?

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Marcus Sheffer LEED Fellow, 7group Aug 21 2014 LEEDuser Expert 42317 Thumbs Up

You must model everything that impacts energy use within the LEED Project Boundary. You determine the project boundary within the confines of the MPRs.

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Ritwik Kakati Dagher Engineering, PLLC
Aug 20 2014
Guest
46 Thumbs Up

Baseline HVAC system exceptions

I modeled a 10-story hotel building. Since the majority of space are hotel rooms, which are considered to be Residential spaces, the primary Baseline HVAC system type is System #1. Of course, there are the nonresidential spaces that exceed 20000 SF, so I modeled them with System #7. I received comments from USGBC reviewer to change the system type for IT rooms & corridors & other spaces to System #3 per G3.1.1 Exceptions b & c. My question is, since the primary HVAC system is System #1, and I'm already applying G3.1.1 Exception a to use System #7, do I have to apply Exceptions b & c on top of System #7? Thanks.

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Marcus Sheffer LEED Fellow, 7group Aug 20 2014 LEEDuser Expert 42317 Thumbs Up

Once you determined the predominant condition, residential, you subtract the area of residential from the total and reenter Table G3.1.1A. You then apply any exceptions to G3.1.1 that apply. You must apply these exceptions. They are not optional.

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Rudolph Carneiro HVAC consultant Sustentech
Aug 19 2014
Guest
574 Thumbs Up

RTS method - TFM method - CLTD/CFM method

Can someone tell me if current simulation software (IES, Energy Plus or even HAP) uses any of the following methods in its calcs?

1. TFM – Transfer Function Method
2. RTS – Radiant Time Series Method
3. CLTD/CLF - Cooling Load Temperature Difference / Cooling Load Factor.

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Marcus Sheffer LEED Fellow, 7group Aug 19 2014 LEEDuser Expert 42317 Thumbs Up

Off the top of my head I do not know. Perhaps the question should be addressed to the Bldg-Sim discussion group at onebuilding.org

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Matt Scott Engineer, N.E. Fisher & Associates, Inc. Aug 20 2014 Guest 241 Thumbs Up

HAP definitely uses the transfer functions. I'm not sure about the others, but I'm sure you can easily find out on www.commercial.carrier.com.

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Santiago Rodriguez Director of Energy Efficiency REVITALIZA CONSULTORES
Aug 15 2014
Guest
816 Thumbs Up

Exterior Building Lighting Power

Hello,

I have a question regarding the Exterior Building Lighting Power. For the project I am working there are a copuple of exterior areas that do not fall in any of the categories of Table 9.4.5 of Ashrae:

1. The perimeter of the project boundary, which has several lighting fixtures.
2. Two sport courts that use several lamps for use at night.

Under which category should I include this areas in order to calculate the baseline exterior power allowance?

Many thanks in advance,

Santiago

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Marcus Sheffer LEED Fellow, 7group Aug 15 2014 LEEDuser Expert 42317 Thumbs Up

Any area that does not fall into a category I would treat as process lighting and model identically. The sport lighting is exempted by 9.4.5-e but must still be included in the models.Perhaps the boundary lighting would be considered a special feature area under the building grounds?

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Santiago Rodriguez Director of Energy Efficiency, REVITALIZA CONSULTORES Aug 15 2014 Guest 816 Thumbs Up

Thank you Marcus,

The boundary lighting could be treated as a special feature, but since that category uses the area to calculate the allowed power, it is a bit tricky how to calculate it, which width should I use? For me it seems more reasonable to just measure the whole perimeter length, but then cannot use the special feature area. Would it be acceptable to use the same levels for both models then?

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Marcus Sheffer LEED Fellow, 7group Aug 15 2014 LEEDuser Expert 42317 Thumbs Up

if it does not fit a category I would model it identically in both.

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Viktor Reutherborg Trainee NCC Construction Sverige
Aug 15 2014
LEEDuser Member
4 Thumbs Up

Vestibules

I'm working on a big building, mostly office but not exclusively, in Stockholm, Sweden. I'm currently working on a restaurant on the ground floor with an entrance from outside. I'ts larger then 3000 square feet but it's not the buildings main entrance. The reason I'm not sure if this entrance needs a vestibule is exception b "Doors not intended to be used as a building entrance" and I found:

"Interpretation: A door that is not a main public entrance to the building is not required to have a vestibule. A controlled access door that opens to a patio which does not have egress from the building’s exterior would not be considered a building entrance door and therefore would not require a vestibule".

This question has probably been discussed earlier but I can't find it and hope someone can help me. Do I need a vestibule on my entrance door for the restaurant?

Thanks

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Marcus Sheffer LEED Fellow, 7group Aug 15 2014 LEEDuser Expert 42317 Thumbs Up

An entrance to a restaurant sounds like a public entry to me. The provision you found is really for side doors that are mostly used as exits or an entrance for a small number of building occupants.

The purpose is to address doors that are frequently opened. I would think that the entrance to a restaurant would qualify.

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Sandra Holmström environmental consultant Bengt Dahlgren AB
Aug 15 2014
Guest
131 Thumbs Up

Interior Lighting Power Requirement in ASHRAE 90.1-2007

I am wondering whether EAp2 requires a project to fulfill the Interior Lighting Power Allowances in Section 9.5 in ASHRAE 90.1-2007 if Option 1 - Energy Modeling is used?

The prerequisite language only states that Mandatory Provisions (Section 5.4, 6.4, 7.4, 8.4, 9.4 and 10.4) in 90.1-2007 has to be fulfilled.

The Building Area Method and Space-by-Space Method is described under section 9.2.2 as well as 9.5 and 9.6.

I understand that either method has to be used in the energy modeling, but is it allowed to e.g. install 12 W/m2 in an office building and in the energy model take a minor penalty due to higher electricity usage in the Proposed model compared to the Baseline model (11 W/m2), as long as the 10 % overall efficiency is achived?

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Marcus Sheffer LEED Fellow, 7group Aug 15 2014 LEEDuser Expert 42317 Thumbs Up

Yes. Since the interior lighting power density is not a mandatory provision it is available for tradeoff. You can go over the lighting energy use as long as you make up the savings elsewhere and get to the minimum percentage.

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Matt Scott Engineer N.E. Fisher & Associates, Inc.
Aug 13 2014
Guest
241 Thumbs Up

Baseline system >70% OA based on 20 degree rise

I have a packaged multi-zone VAVVariable Air Volume (VAV) is an HVAC conservation feature that supplies varying quantities of conditioned (heated or cooled) air to different parts of a building according to the heating and cooling needs of those specific areas. proposed system that has a 25 ton load and is scheduled with 10,000 cfm supply air and 4550 cfm outside air (45.5% OA). This system has significantly fewer operating hours that the majority of the building (which is type 5 for the baseline) so for the baseline building it was split off as a separate system type 3. When I run the baseline system based on a 20 degree rise, and then override the ventilation to match the proposed, it comes out at 5,888 cfm supply air and 4550 cfm outside air (77.3% OA). The tonage would require it to be a 20-25 ton unit at 8,000-10,000 cfm supply air in reality which would bring the OA fraction down to 57% or less.

The proposed system does have heat recovery although it is not required, and the baseline system already has demand control ventilation . I'm guessing I have to model the baseline unit with heat recovery, right? It doesn't meet any of the exceptions listed under G3.1.2.10.

Or should this baseline system be another type 5 packaged VAV system?

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Jean Marais b.i.g. Bechtold DesignBuilder Expert Aug 14 2014 LEEDuser Member 8474 Thumbs Up

This touches on the zone required minimum outdoor air (ODA_min) specified in the proposed design. This specification must be the same for both proposed and baseline models. It does not, in my humble opinion, mean that those rates are not exceeded at different points in time by either model. In fact, due to the models having different HVAC systems often including economizers and so on, it makes sense that the actual ODA rates will differ between models at any hour in the simulation.

The exception to the ODA_min specification being the same for both models is the demand controlled ventilation (DVC). If the proposed model has DVC, then the baseline must also have DVC, but with the ODA_min set to those in ASHRAE 62.1 (which implies that the DVC for the baseline controls on occupant sensor, which does not have to be the case for the proposed model, for example, which may model CO2Carbon dioxide based control).

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Matt Scott Engineer, N.E. Fisher & Associates, Inc. Aug 14 2014 Guest 241 Thumbs Up

The proposed system is a multi-zone VAVVariable Air Volume (VAV) is an HVAC conservation feature that supplies varying quantities of conditioned (heated or cooled) air to different parts of a building according to the heating and cooling needs of those specific areas. unit with heat recovery, but it does not have CO2Carbon dioxide controls for ventilation. Per G3.1.1 exception b, the baseline system a type 3 single zone unit. Is this correct or would it be better to model it as another type 5 multi-zone VAV system?

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Jean Marais b.i.g. Bechtold DesignBuilder Expert Aug 14 2014 LEEDuser Member 8474 Thumbs Up

I would model a 3-PSZ-AC for each zone to which the G3.1.1 exception b applies. If the proposed system has no DCV, then why have you modelled it so in the baseline as stated in your last post?

The reason for splitting off "different load" zones from the system 5, is that it becomes impossible to optimally cool and heat both zone types. Using an extra system 5 may work if all the zones connected to it have the same load profiles, but is allowed only under exception a), i.e. if the sum of your "different load" zones is more than 1900 m2.

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Marcus Sheffer LEED Fellow, 7group Aug 14 2014 LEEDuser Expert 42317 Thumbs Up

You are in good hands with Jean.

One thing I would say that I often seen design engineers struggle with is the attempt to design the baseline system. Often the baseline system cannot be designed or the end result does not make design sense. It is what it is.

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Matt Scott Engineer, N.E. Fisher & Associates, Inc. Aug 14 2014 Guest 241 Thumbs Up

The proposed system I am talking about covers 11,000 sqft (entire building is 82,000 sqft) and is sized at 25 Tons and 400 CFM/Ton for a total of 10,000 CFM supply air including 4550 CFM of outside air (about 46% OA). It contains 11 zones, all of which are simultaneously occupied and only for a few hours per week while the majority of the building is occupied 70+ hours per week. This proposed system requires demand control ventilation due to the occupant density in several of its zones, but not heat recovery since the OA fraction is less than 70%. However, the proposed design does have heat recovery, thus the demand control ventilation is not required based on 6.4.3.9 exception a. And just for clarification, I am referring to 90.1-2007.

For the baseline building, I took exception b and split this system off as a single type 3 system. Now when it's auto-sized based on a 20 degree rise, it comes out at 5,888 CFM supply air. Correcting the ventilation to match the proposed case (4550 CFM outside air), it comes to 77% outside air. Since this outside air fraction is above 70%, the baseline system must have heat recovery modeled per G3.1.2.10. And it's required to have Demand Control Ventilation based on the occupant density mentioned in the proposed case. However, since Heat Recovery is required, Demand Control Ventilation is not required. Do I have all that right?

As for the proper baseline system type for this part of the building, is a single zone type 3 system ok? Do I really need to split it into 11 single zone type 3 systems? Or would it be better to make it a single type 5 multi-zone system even though it covers less than 20,000 sqft of the building? I've been told before the 20,000 sqft rule is not an absolute rule. What would best practice in the eyes of a reviewer?

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Marcus Sheffer LEED Fellow, 7group Aug 14 2014 LEEDuser Expert 42317 Thumbs Up

All sounds right in first two paragraphs.

Regarding the zones you still need to follow the rules for creating thermal blocks from Table G3.1-7,8 or 9. In general you do not have a choice when modeling the exceptions to G3.1.1, they are required. Exception a only applies to the examples given (residential/non-residential and fuel source) and the 20,000 sf is pretty absolute.

Best practice to the reviewer is to follow the rules and principles of Appendix G. If you have a doubt about what is the best way to do something then it is best practice to do that which produces the most conservative results.

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