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 15% of the total available points in LEED are at stake. Master the minimum requirements under EAp2, and you will be well on your way to earning points under EAc1. Keep in mind that any LEED-NC v2.2 project registered after June 26, 2007 must achieve at least two energy use reduction points via EAc1 methodology. Plan for this in your approach to EAp2.
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.
All projects must meet all the mandatory provisions (Sections 5.4, 6.4, 7.4, 8.4, 9.4, and 10.4) of ASHRAE/IESNA Standard 90.1-2004 (without amendments).
There are prescriptive compliance paths available for the prerequisite. However, all projects registered after June 2007 have to obtain two points under EAc1, which offers three compliance paths. You probably should choose a compliance paths that allows you to achieve both EAc1 and EAp2.
If energy modeling is not planned for the project, must meet either the prescriptive requirements (Sections 5.5, 6.5, 7.5, and 9.5) of ASHRAE 90.1-2004 (without amendments) or as selected for EAc1.
Energy modeling 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 90.1-2004 for all major components, including the envelope, HVAC, lighting, and domestic hot water. The best way to do is look up the list of mandatory requirements and fill the ASHRAE 90.1 compliance forms.
Second, you need to demonstrate energy cost savings as determined for EAc1 point goals for your designed building compared with a baseline case meeting the minimum requirements of ASHRAE 90.1. You can do this by creating a computer model following rules described in Appendix G of ASHRAE 90.1, or pursuing one of the other EAc1 compliance paths.
Computer modeling offers the following key advantages:
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 ASHRAE prescriptive compliance paths are a good way to earn the prerequisite simply by following a checklist.
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.
As a general rule that applies to all energy credits, 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.
If your building includes the use of purchased steam supplied to your HVAC system, the proposed (design) building should be modeled as if the steam system is “located” in the building—with the same efficiency with which it typically operates. The designed building is allocated only the fuel cost (for natural gas or oil) required to generate and deliver the steam needed for the building. The steam purchased is actually considered “free,” as steam rates are not included. And here is where your building really benefits—if the steam system also co-generates electricity along with steam, that electricity is assumed to be “free” to the proposed building, as well. (Refer to the latest guidelines from USGBC.)
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 big picture goals for the project 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.)
You will need to comply with the mandatory requirements of ASHRAE 90.1-2004, to bring your project to the minimum level of performance. The ASHRAE 90.1-2004 User’s Manual is a great resource, with illustrated examples of solutions for meeting the requirements.
Check the registration date of your project. If you registered after June 2007, you have to achieve two points under EAc1 as per USGBC addenda. There is lot of synergy between EAc1 compliance and meeting this prerequisite because of this reason. The prerequisite’s energy-reduction target (for EAc1 option 1) of 14% is not common practice and is considered beyond code compliance.
If you registered before 2007, you have a lower threshold and can follow the AHSRAE 90.1 2004 prescriptive compliance path. You do not technically have to earn any points in EAc1.
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.
Remember that the ASHRAE 90.1-2004 mandatory provisions and prescriptive and performance requirements are a starting point for energy efficiency. Plan to exceed these to earn points under EAc1.
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:
All compliance path options may require both the architectural and engineering teams to take some time in addition to project management to review the ASHRAE prescriptive checklists, fill out the LEED Online submittal template, and develop the compliance document.
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 in the Basis of Design.
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.
Load reduction requires coordinated efforts by all design members including the architect, lighting designer, interior designer, information-technology manager, and owner. While ASHRAE 90.1-2004 is a good starting point for this effort, don’t plan to stop there:
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:
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.
Review and reconfirm compliance with the mandatory requirements of all the relevant sections of ASHRAE 90.1-2004
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.
Of equal importance, make sure that any scope reductions or design changes don’t jeopardize meeting the ASHRAE 90.1-2004 requirements.
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.
The mechanical engineer, lighting consultant, and architect revisit the ASHRAE checklists 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 should track the status of each requirement on an on-going basis, through design iterations.
While the LEED Online submittal template does not require detailed documentation for each requirement, it is important that each item be documented in supporting documents and submitted to be reviewed by the rest of the team and the GBCI reviewer.
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.
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.
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.
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.
Most of the documentation for EAc1 is shared with EAp2. Don’t forget to document the mandatory provisions of ASHRAE 90.1 2004 for EAp2 compliance, however, because that will not requested in EAc1.
Excerpted from LEED for New Construction and Major Renovations Version 2.2
Establish the minimum level of energy efficiency for the proposed building and systems.
Design the building project to comply with both—
Design the building envelope, HVAC, lighting, and other systems to maximize energy performance. The ASHRAE 90.1-2004 User’s Manual contains worksheets that can be used to document compliance with this prerequisite. For projects pursuing points under EA Credit 1, the computer simulation model may be used to confirm satisfaction of this prerequisite.
If a local code has demonstrated quantitative and textual equivalence following, at a minimum, the U.S. Depart- ment of Energy standard process for commercial energy code determination, then it may be used to satisfy this prerequisite in lieu of ASHRAE 90.1-2004. Details on the DOE process for commercial energy code determi- nation can be found at www.energycodes.gov/implement/determinations_com.stm.
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.
Useful web resource with information on local/regional incentives for energy-efficiency programs.
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.
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.
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.
Research center at RPI provides access to a wide range of daylighting resources, case studies, design tools, reports, publications and more.
International association of energy modelers with various national and local chapters.
Non-profit organization aiming at design community to increase collaboration for designing energy efficient buildings.
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.
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.
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.
A guide for achieving energy efficiency in new commercial buildings, referenced in the LEED energy credits.
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.
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.
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).
Required reference document for DES systems in LEED energy credits.
This website discusses the step-by-step process for energy modeling.
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.
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.
Free download of AHSRAE energy savings guide, use for Option 2.
Research warehouse for strategies and case studies of energy efficiency in buildings.
An online window selection tool with performance characteristics.
This website lays out design process for developing an energy efficient building.
This website discusses ways to improve design for lower energy demand as they relate to the AIA 2030 challenge.
This website includes discussion of design issues, materials and assemblies, window design decisions and case studies.
This site lists multiple web-based and downloadable tools that can be used for energy analyses.
This database is maintainted by the California Energy Commission and lists resources related to energy use and efficiency.
Energy design tools are available to be used for free online or available to download.
This website lists performance characteristics for various envelope materials.
This is an online forum of discussion for energy efficiency, computer model software users.
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.
This directory provides information on 406 building software tools for evaluating energy efficiency, renewable energy, and sustainability in buildings.
Weather data for more than 2100 locations are available in EnergyPlus weather format.
Weather data for U.S. and Non-U.S. locations in BIN format.
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.
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 statistics from the U.S. government.
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.
2008 guidelines and performance goals from the National Science and Technology Council.
This website offers information on energy efficiency in buildings, highlighting success stories, breakthrough technology, and policy updates.
Bimonthly publication on case studies and new technologies for energy efficiency in commercial buildings.
AIA publication highlighting local and state green building incentives.
Information about energy-efficient building practices available in EDR's Design Briefs, Design Guidelines, Case Studies, and Technology Overviews.
DOE tools for whole building analyses, including energy simulation, load calculation, renewable energy, retrofit analysis and green buildings tools.
This is a computer program that predicts the one-dimensional transfer of heat and moisture.
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.
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.
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.
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.
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.
In your supporting documentation, include spec sheets of equipment described in the Option 1 energy model or Options 2–3 prescriptive paths.
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.
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.
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.)
The climate zones shown on this Department of Energy map are relevant to all options for this credit.
This sample EAc1 LEED Online credit template shows documentation of a project using the California Title 24 energy code.
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.
This template is the flattened, public version of the dynamic template for this credit that is used within LEED-Online v2 by registered project teams. This and other public versions of LEED credit templates come from the USGBC website, and are posted on LEEDuser with USGBC's permission. You'll need to fill out the live version of this template on LEED Online to document this credit.
Documentation for this credit can be part of a Design Phase submittal.
I am busy with my first LEED project. In South Africa we usually use Green Star which is based on the Australian system. I would like to ask you a question regarding appendix g from 90.1-2007.
Regarding the maximum window-wall ratio of 40% mentioned in 188.8.131.52.1, the manual only says "gross wall area". Does this mean that the total glass area of the entire building must be < 40% of all the walls or is this per orientation? If it is per orientation, is it for the 4 or 8 orientations? Does this include semi-conditioned or is it only conditioned zones? The building which I am modelling is very complicated with many different zones and orientations.
I also would like to ask a question regarding regions. The building is in Swaziland. Swaziland is not listed in any of the tables. Table B-4 however lists different conditions for the zones. I am unsure what CDD10°C and HDD18°C. Could you direct me to any info on how to select the zone? Any help you could give would be appreciated.
Could you please post this in the LEED 2009 EAp2 forum since the question relates to that version of LEED? Any one looking for answers in the future will be able to find if it is in the correct forum.
During energy modeling, do we have to use break horsepower or Rated horsepower?
Roof top unit in one of the project have 9.64 BHP and 15 Hp (rated).
which one should i have to use during modeling?
BHP represents to actual motor work under a load. This gets translated to kW times hours of use equals kWhA kilowatt-hour is a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 Btu.. Use break horsepower.
Hi, I am currently working on a project which is a multi-story new tower to an existing building. There is new chillers, heat pumps, etc. Hot water used for heating is primarily from GSHP, at around 120F to 130F. Then the water will go into a heat exchanger (steam, water) to get up to 140F and another exchanger to get up to 180F. All those equipment so far are new addition and we have included them in our energy model. But the heat exchanger is getting steam from existing plant (steam boilers, the boilers is serving both new addition and existing building). So how do we model our heating side for LEED? Should we include boilers? Or we can just do exceptional calcs for it? and maybe update our GSHP to reflect the calcs?
The good news is that you have options, the bad news is that you have options. There are two primary issues here - whether and how you model the plant.
G3.1-2 Proposed indicates that you have to model the whole load on the central plant so you account for the actual part-load efficiencies. There are ways to do so without having to model the whole existing building as well but you would need to simulate the effect of the whole load on the plant.
You could treat it as purchased energy and avoid the part-load issue. You then have multiple options - Appendix G, addendum ai and DESv2 Option 1.
You can also look at DESv2 Option 2.
So how you model it depends on the approach you select. This should not require an exceptional calculation.
I am working on model for LEED v2.2 NC. The standard for this version is 90.1-2004. Since it is not required to comply with the 90.1 amendments, am I correct that I can use the fan power calculation for 90.1-2004 as calculated in the fan power calculator posted in the tools section? The fan power calc for 2004 gives me a value of ~.8w/cfm while the 90.1-2004 has been updated to required baseline of .3w/cfm.
Correct you are not required to apply the addendum.
Sounds like a system 1 or 2. Yes the original fan power allowance was very high.
In a scenario which an onsite biomass plant uses an ineligible bio-fuel as a main heating source (backed up via natural gas) in the proposed case, and the baseline system is a fossil fuel furnace - How should the fuel costs be treated?
My understanding is that the biomass should be modelled with the purchase rate for the proposed case and that the base case should be exactly the same so no credit is claimed. The bio-fuel is ineligible and therefore not a 'renewable' source of energy - the baseline should not be modelled with the backup energy source per G2.4.
Your understanding is correct.
I have a question about calculating Window to wall ratio with unconditioned above-ground garage space. should I include only the wall area for conditioned space or it should include complete facade?
30% of my proposed building east wall is garage exterior surface, so when I generate the baseline 40% WWR, should this area be included in the calculation?
Thanks in advance.
Conditioned spaces only.
I am doing Energy modeling that includes office spaces, dining and kitchen area. Do i have to provide all equipment plug load from kitchen area same for baseline and proposed (can we exclude kitchen equipment plug load).
Kitchen is commercial type and it involves high amount of plug load.
It must be included identically in both models.
If you want to claim any savings for the kitchen equipment you must do so as an exceptional calculation.
If we provide all kitchen equipment plug load, than total energy consumption will be very high (kitchen equipment plug load will be above 25% of total energy consumption). and energy saving from HVAC equipment will be insignificant, which make total saving very low.
Do we have to consider plug load above 25% also.
I am not claiming saving for kitchen equipment.
Yes you must model all energy use within and associated with the project. There is no 25% minimum. You model the project as accurately as you can. If you are over 25% then do nothing. If less than 25% explain why you are less.
As per ASHRAE 90.1-2007 all baseline buildings must be modelled with water cooled type chillers.
Is it possible to model a baseline building with air cooled chiller? If yes, Is that strategy accepted by LEED.
The baseline system depends on the use type, area, number of floors, and heating fuel type. There are many baseline systems that do not require water cooled chillers. The baseline building is defined by Appendix G. See Table G3.1.1A.
Also please note that you are in a LEED v2.2 forum and that version of LEED references ASHRAE 90.1-2004.
in a project that the first floor is on the level 0 by mezzanine, should I include the voids areas for the Lighting Power Density calcullation? or exclude it?
In general you only use the floor area so exclude it.
In ASHRAE 90.1 2007, G3.1.1 states: "For systems 1,
2, 3, and 4, each thermal block shall be modeled with its own
If you are using Trane Trace to do your PRM modeling, and your proposed design is a 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. system, this can result in a very large number of systems in the baseline model. Modeling such a large number of systems creates a lot of extra work for the modeler and introduces more opportunity for error.
In Trace, the modeler can select the system "Constant Volume, Single Zone", which has a zone level fan, cooling coil, and heating coil. This allows each zone to act as an independent thermal block. If the rooms are assigned to zones the same as in the proposed case, then the thermal blocks will be identical.
In my opinion, the intent of 90.1 would be met, but I am concerned that my design submission for LEED certification will get rejected by the reviewer based on the semantics of the language in 90.1.
The only real influence that this issue has on energy savings is that the system size in the baseline will be larger, which will change the minimum efficiency requirements. Larger, packaged DX systems have less stringent efficiency requirements than their smaller counterparts. I have not found any language in the 90.1 Commentary that addresses this issue as it relates to thermal blocks.
In my professional opinion, it is unrealistic to model a 25,000 square foot office building with 25 distinct rooftop units, as this would absolutely NEVER happen in the real world. I believe that the most reasonable compromise is to model the baseline case with the rooms assigned to the same zones and the zones assigned to the same systems, as they are in the proposed model.
Has anyone dealt with this issue in the past? What was your experience with the review process?
The real world and the baseline have nothing to do with each other! Too often engineers try to "design" the baseline and that is a mistake.
Explanations go a long way in the review process. If you are doing something that you think may be an issue explain what you did and why you did it.
More specifically the key is the creation of thermal blocks in the Proposed case. See Table G3.1-7 Proposed. You are allowed to create these blocks according to those rules and then the baseline must be modeled the same. So the reviewer should not question the baseline efficiencies if you correctly followed those rules. Be prepared to defend or explain how you created those blocks.
You are correct that this affects the "savings" but there is nothing that prevents you from doing it.
What is the difference between energy cost budget method and appendix g? When one should be used over the other?
The ECB is a code compliance method to allow projects who may not meet all of the prescriptive components of the standard to demonstrate compliance using a performance path. Appendix G is a methodology for predicting energy savings and is not a formal part of the standard relative to compliance.
LEED uses Appendix G.
Comment from reviewer: "It is unclear why there is a significant discrepancy in the fan equivalent full load hours (determined by dividing the total energy consumption by the demand) between the Baseline Case (2,210 hours/year) and the Proposed Case (1,784 hours/year)."
Im not really sure what they mean by this since when I divide total energy consumption by the demand Im not getting these numbers they are referring to. Any insight for Trace 700?
Basically this gives you the fan run hours per year. You should be able to replicate these numbers. Are you just using the fan energy consumption and demand? Are you still showing a similar difference in hours? The exact numbers do not matter, the difference does and the magnitude of the difference relative to the result also matters. If the difference remains is there an explanation for the disparity? Are the schedules identical?
They seem to be identical, I'm just trying to understand where he/she is getting that number in order to me to find out how the origin of it.
Hard to say without seeing the documentation.
I found it for Trace700 it was under the equipment energy consumption.
Not really sure where the discrepancy is coming from. 426 hours/year but the schedules are exactly the same. We submitted this info to CDS Trace and they agreed the comment does not make sense. In reality this difference should not be equal because the efficiency of the equipment is different in the proposed and the baseline
The reviewer is asking you to explain the difference. So explain the difference in your response.
From our experience in energy model I would state is that it is improper, from my point of view, to generically sum up the total of the demand energy rates for all of the individual fans in one alternative and divide them into the total kWhA kilowatt-hour is a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 Btu. consumed by the fans in that alternative and then compare this value to a different alternative with DIFFERENT sizing calculations and DIFFERENT loads and make the assumption that something is wrong. Therefore we will try to elaborate this in the response but it would be great if anybody has gone through the same.
I have gone through the responses on this issue dozens of times. This type of comparison is proper when evaluating the accuracy of the modeling results. Let me give you an extreme example. Suppose the run hours in the baseline were 8760 hours/year and in the proposed 3000 hours/year? The baseline fans are running all the time and the proposed are not. Clearly there is something wrong. Your situation is not that extreme so perhaps there is nothing wrong. The reviewer just can't figure out why the difference is what it is.
I agree that there could be many reasons why the hours are different. The reviewer is not saying they should be identical. Based on the portion of the reviewer comment you provided they are just unclear why there is the level of difference they are seeing. This means they looked at the documentation you provided and cannot figure out why there is the magnitude of difference shown in the results. For me or anyone else in this forum to tell you why there is this difference is not possible without seeing the documentation you provided that would affect this issue. So we can't tell you what to do beyond examining your modeling input and results (assuming you have modeled it all correctly) and providing an explanation for the level of difference. The difference may not really be that significant and perhaps there is a simple explanation. So try to just provide an answer to this question - Why would the fans in your baseline model run about 20% more hours a year than the fans in your proposed model?
Here might be an example of a plausible explanation - the proposed building envelope is much better, which reduces heat loss (gain), which means a much smaller load so the fans run less to meet that lower load. You should elaborate more and use any specific examples and/or data you have to back up your explanation but hopefully you get the idea. If you have a good explanation your reviewer should be happy.
Hello. I got a fenestration tecnical data and there is a g-number. I haven´t been able to find a convertion factor to SHGCSolar heat gain coefficient (SHGC): The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. or SC.
does anybody know how to convert them?
I never heard of a g-number.
SHGCSolar heat gain coefficient (SHGC): The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. can be the equivalent for the European G value, if SHGC refers to the solar energy transmittance of the glass alone.
The only difference between the numbers is that SHGC uses an air mass of 1.5 and the g value uses an air mass of 1.0.
I am working on a project and the client wants to include time clocks in two separate electrical circuits from lighting system. Each circuit include half of the luminaires (same zone) and it will be set according to the following:
-Circuit 1: 8 a.m. until 23 p.m.
- Circuit 2: 18 p.m until 23 p.m.
Note: one circuit meets the minimum illuminance levels during the day, in 75 % of all year.
Regarding this, can we simulate Baseline and Proposed buildings with different schedules assuming that this is an "automatic control for daylight utilization?Which document shall we provide?
You can try.
Since you are changing a schedule you will need to submit this as an exceptional calculation. Provide a narrative explaining what you are doing and justifying your baseline situation. Provide separate calculations/modeling run to show your savings separately in Section 1.7 in the form.
I am attempting to determine R values of my building's walls to satisfy the response from my reviewer on the energy model and am a little confused about a few things:
1. Where can I find the R-value for brick? Appendix A seems to deal specifically with concrete and CMU, but gives not guidance on brick.
2. Where am I supposed to determine the derated R-value for closed cell spray foam that has been put on the interior face of a masonry wall. NOTE: 1 5/8" hat channels have been attached to the wall at 24" O.C. and gyp board attached to the hat channels; therefore, the spray foam is essentially between the hat channels. Do I use table A3.1D to get the derated value of the insulation?
I really appreciate any assistance that can be provided. Thanks - Todd
1. The Fundamentals Handbook has a table with the R-value of a vat array of materials.
2. Looks like A3.1A fits best and just adjust for the difference between the concrete and brick. A3.1D appears to be for walls with studs in them. You could also to to section A9 for an alternative methodology.
Ouch...my R-6 /inch closed cell foam insulation (10.4 for 1 5/8" thick) has a derated value of around R-2.6, and that includes the air film and gyp board? This seems a bit conservative; is there no way to go at this a different way and get a better R-value? I really appreciate your help!
I am not sure how you came up with the value that you did. R6/inch for 1 5/8 " is R9.75. If you used A3.1A I come up with about an R8.7 with the 1 in clip 24" OC under the concrete column. You would then subtract the R-value difference between brick and concrete so is would be slightly less. Maybe I am missing something.
for the EA pre-requisite 2:minimum energy performance, what does annual equivalent full load hours of DHWDomestic hot water (DHW) is water used for food preparation, cleaning and sanitation and personal hygiene, but not heating. operation mean?? this is for the table 1.4.5 - service water heating. Can any one clarify this??
From your DHWDomestic hot water (DHW) is water used for food preparation, cleaning and sanitation and personal hygiene, but not heating. schedule add up the hourly fractions for each hour. For example, if your hourly fraction is 0.5 for each hour of the year then it would be 8760 hours/year times 0.5.
thank you so much
V 2.2 NC - we would like to reference an acceptable day light simulation
model to a new building.
Is a sketch up model with a dimsim calculation an acceptable reference with the Carrier model for day light ? Also is it acceptable for the
Daylight credit? Please advise with any clarifications... Thank you, Suzy
We use DaySim and it should be acceptable for simulating daylighting performance.
Hello Marcus - The other part of the question is that the model is
a google sketch up model - will this be acceptable for both
Optimizing Energy and Day light credit? Any draw backs to this
program/model combination? Thank you, Suzy
Sketch Up just creates the geometry so the combination should be fine.
Hello. We are using the prescriptive path on a CI2.0 project. The project was registered after June 26 2007, so the project will need to be compliant with the prerequisite by earning 2 points under EAc1. Out of the 4 prescriptive options, the project will only be compliant with EAc1.4 Equipment and Appliances. The project will earn the prerequisite 2 points via the NEW purchases it is making, which will be 100% Energy Star certified. The LEED CI 2009 addenda clarified that projects can earn EAc1.4 with new purchases only. Do you foresee any problem with an older CI2.0 project earning compliance with new purchases and using that to meet the 2-point prerequisite. Any comment is appreciated!
I don't see an issue.
We modeled our building using eQuest, from eQuest we get as simulation result the Building energy performance report BEPS and building utility performance report BEPU. The values in the BEPR for example are in MBtu, whereas the ones in the BEPU are in KWHA kilowatt-hour is a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 Btu.. Which piece of information should be used to fill out the energy use in the templates?, from the unit conversion specified in LEED, the MBtu values when converter to kWh, are less than 1/1000 of the results in the BEPU. Are we doing the unit conversion wrong? should we just use the BEPR results and disregard the BEPU results?
Sounds like the conversion is off. Are you assuming 1000 BTUA unit of energy consumed by or delivered to a building. A Btu is an acronym for British thermal unit and is defined as the amount of energy required to increase the temperature of 1 pound of water by 1 degree Fahrenheit, at normal atmospheric pressure. Energy consumption is expressed in Btu to allow for consumption comparisons among fuels that are measured in different units. or 1 million BTU?
I would recommend that you use the BEPU results for entering in the template.
I am working on a project with a limited site. The proposed building (six story hotel) has a distinct size that only fits on the site one way. How should I address Criteria 1.3: Building Configurations in order to pass the exploration of the alternate building configurations? Thanks.
Building footprintBuilding footprint is the area on a project site used by the building structure, defined by the perimeter of the building plan. Parking lots, parking garages, landscapes, and other nonbuilding facilities are not included in the building footprint. is only one aspect of configuration. Other aspects are discussed in the Core Performance document. This requirement is intended to encourage you to explore potential configuration options that may result in lower energy use.
I am working on a project that was denied EAp2 in final review due to a discrepancy in an exceptional calculation we provided. To summarize, we were having a hard time modeling the energy savings of ERV units in Energy Pro so we modeled the savings in excel separately. The reviewer pointed out that the energy savings of the ERVs was 89% of the total heating and cooling load of the building (which they believe is unlikely) and threw away the savings resulting in a total building energy savings of 8.5% and denial of EAp2. Upon investigating the entire building model we found that using the LEED module in Energy Pro (we had previously used the T24 module) the building performed 12.2% better WITHOUT modeling ERVs. I have also found a way to model ERVs, however it has no practical effect.
Regarding submitting an appeal, will LEED accept our revised energy model? What documents will I need to submit in order to ensure an open and shut acceptance of our appeal?
The exact opposite happened to one of my projects.
Exterior to the building process loads accounted for 95% of the total cost use. The energy cost savings for the ECMEnergy conservation measures are installations or modifications of equipment or systems intended to reduce energy use and costs. was about 38%.
The building without exterior process loads, but including building process loads, had an energy cost savings, also, of about 38%.
The reviewer challenged the ECM, but forced the project to keep the ECM. In your case they forced your project to remove it.
This type of game playing by reviewers does not surprise me. Why claim one project must keep an ECM, and another not, has no justification.
In our case the ECM was highly specialized. Only two engineering firms in the United States are qualified to design the systems. The LEED reviewer decided they were more qualified to determine what the ECM system design should be than either of the two qualified firms.
I would love to find out who the ECM reviewer was, to investigate what qualified them to design the ECMs, which were related to critical life-support of animal species. My guess, is they had no qualifications whatsoever. Yet, their opinion stood. The GBCI could do nothing about the review comment once the reviewer "invented" it.
I am sorry to say, that there is no way to know what the reviewers want for ECMs. It is a completely blind part of LEED Energy Analysis, one where reviewers can make up their own rules. Rules that are often wrong, but somehow become hardcore LEED requirements.
That there can be two completely different sets of LEED ECM requirements, it of great interest to me. That means the requirements are not applied evenly, or fairly, by the reviewers.
I assume that the LEED module is using 90.1- Appendix G. If everything is in order then there should be no reason the revised model would not be accepted. Be sure to include a thorough explanation of what you have done and provide the documentation requested. Make sure to examine the modeling results submitted for the final and the appeal and explain any major differences in the results and/or the inputs.
Thanks Marcus. I've now gone even deeper into the model and realized that Energy Pro models the incorrect baseline HVAC system. I would like to implement a work-around into the model to get it to model the correct baseline. The system is a VRF heat pumpA type of heating and/or cooling equipment that draws heat into a building from outside and, during the cooling season, ejects heat from the building to the outside. Heat pumps are vapor-compression refrigeration systems whose indoor/outdoor coils are used reversibly as condensers or evaporators, depending on the need for heating or cooling. In the 2003 CBECS, specific information was collected on whether the heat pump system was a packaged unit, residential-type split system, or individual room heat pump, and whether the heat pump was air source, ground source, or water source. and Energy Pro models it against a packaged 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. while it should be modeled against a packaged heat pump since there is no gas available on site. There is an acceptable and published work around for modeling VRF systems for Title 24 compliance.
If you cannot speak to my specific case about the VRF system, can you please advise whether implementing a published acceptable work around in the energy model and resubmitting the appropriate documentation will be acceptable for an appeal?
I do not see anything in what you are suggesting that would unacceptable for an appeal.
Nevermind... Found an answer to my question.
42, the answer is always 42.
I am not sure to understand the G184.108.40.206 Equipment efficiencies of appendix G. My question is: for the system 4-PSZ-HP packaged rooftop heat pumpA type of heating and/or cooling equipment that draws heat into a building from outside and, during the cooling season, ejects heat from the building to the outside. Heat pumps are vapor-compression refrigeration systems whose indoor/outdoor coils are used reversibly as condensers or evaporators, depending on the need for heating or cooling. In the 2003 CBECS, specific information was collected on whether the heat pump system was a packaged unit, residential-type split system, or individual room heat pump, and whether the heat pump was air source, ground source, or water source., Which table belongs the system 4 (among 6.8.1 tables)?
It's not clear to me if the baseline geometry is allowed to be different from the proposed building geometry. (with the same area of floor, wall, roof and fenestration(if <40%), numbers of floors, exposed perimeters of concrete slabs on grade ...)
In order to transform an irregular floor area to a rectangular one.
The baseline geometry must be identical to the proposed. The only exception is the glazing area if the proposed is over 40% window to wall.
May I define the baseline building as a single zone with an internal thermal mass, and the proposed as different zones?
The Proposed is always defined as it was designed/built.
Baseline is defined by Appendix G. There is not enough information to answer your question about the zoning.
Hi Marcus! Thanks for your answer, and sorry for don't be specific.
What I mean is that in the proposed building, I have defined different thermal zones, each one with the own heating or cooling system (how it is designed).
But in the baseline building I have to introduce the system PSZ-HP packaged rooftop heat pumpA type of heating and/or cooling equipment that draws heat into a building from outside and, during the cooling season, ejects heat from the building to the outside. Heat pumps are vapor-compression refrigeration systems whose indoor/outdoor coils are used reversibly as condensers or evaporators, depending on the need for heating or cooling. In the 2003 CBECS, specific information was collected on whether the heat pump system was a packaged unit, residential-type split system, or individual room heat pump, and whether the heat pump was air source, ground source, or water source. ( as says Appendix G) for all the zones of the building. When it is simulated, the reports shows me that there is too much unmet hours in the baseline building.(There is just a thermostat for control the UTA, which is situated in a zone of the building that I can choose).
In order to solve it, I though to remove the internal walls, and add an internal thermal mass.
My question is: Is it correct to have the proposed building with internal walls and the baseline building without?
The internal walls do not matter so much as they are typically adiabatic. What matters are the zones or thermal blocks. The baseline needs to follow G3.1.1 and Table G3.1-7. Also you cannot add mass to the baseline if it does not exist in the proposed.
Unmet load hours are often the result of schedules. I would start there first. When are your unmet load hours happening?
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