This prerequisite can be a major hurdle for LEED-CI projects. When challenges arise, it’s most often because project teams don’t review the requirements early enough in the process to incorporate them into the design. Some teams assume that these requirements follow standard practice—but in some cases they do not.
The prerequisite demands that teams comply with a number of prescriptive measures, along with requirements for lighting power density reductions and meeting performance thresholds for equipment efficiency based on the ASHRAE 90.1-2007 standard.
The LEED-CI project scope includes only the systems being installed within the scope and budget of the interior fit-out of the project. Base buildingThe base building includes elements such as the structure, envelope, and building-level mechanical systems, such as central HVAC, and materials and products installed in the project (e.g., flooring, casework, wall coverings). systems that are not part of the leasable area occupied by the interior space are not addressed here.
This credit usually falls under the responsibility of the mechanical engineer, but the lighting designer, architect, and owner all must contribute to designing an energy-efficient project that meets the owner’s goals as well as the LEED requirements.
This prerequisite refers to ASHRAE 90.1-2007, Sections 5–10, for mandatory provisions and energy-efficiency requirements via a prescriptive or performance-based approach for the project’s envelope, HVAC, service water heating, power, lighting, and other equipment as defined by ASHRAE. In addition, it mandates installation of Energy Star-labeled equipment and appliances.
Projects in California may use Title 24-2005, Part 6 in place of ASHRAE 90.1-2007.
This credit addresses four components of energy use in reference to ASHRAE 90.1–2007.
All ASHRAE requirements can be documented using ASHRAE compliance forms.
This prerequisite establishes the project’s energy performance so that the project can demonstrate a commitment to energy efficiency. The energy use of a LEED-CI project, in terms of the ASHRAE 90.1–2007 standard, must meet four distinct requirements:
Identify the elements of the project that fall under this prerequisite: space cooling, space heating, lighting, ventilation, pumping, and domestic hot water. Do this by reviewing the requirements in ASHRAE 90.1-2007 and developing a building systems narrative for equipment and lighting.
LEED-CI energy systems relate to only those building systems within the construction or remodeling scope of the project. They do not address base building systems outside the interior fit-out. Applicable systems typically include lighting, HVAC distribution, service water heating, and equipment and appliances. The envelope is usually completed as part of the base building. It is only when the envelope is altered in the tenant scope that a CI project must address the requirements listed in the prerequisite.
The owner and project team should determine the project’s energy efficiency goals and include them as part of the owner’s project requirements (OPR) and Basis of Design.
Having the owner take an active role in developing and maintaining energy efficiency goals for the project can be helpful to the project team. Stating goals in terms of a “minimum acceptable level” and a “specified payback period” is an effective way to articulate goals. For example: “Our goal is a minimum 30% reduction in lighting and HVAC energy usage” or “to implement efficiency measures with paybacks of less than 5 years.”
Consider integrating high-efficiency HVAC equipment into your design.
Efficient design can have synergistic benefits. For example, low lighting power density (LPD) translates to a smaller cooling load, which results in a smaller cooling system size and lower energy bills for lighting and cooling, which are the largest demands in most office buildings.
Many local incentive programs offer rebates for efficiency measures. Identify any available incentives at this time to inform your design decisions for equipment selection. Also look for incentives for energy optimization during the design process, like utility-funded energy modeling programs. (See Resources for help finding incentives.)
The prerequisite includes meeting the mandatory requirements for each of the six sections of ASHRAE 90.1-2007.
These six sections include all major energy-using components of a building project:
The MEP team should become familiar with the minimum efficiencies required for heating, cooling, and hot water equipment listed in ASHRAE 90.1-2007, Tables 6.8.1 and 7.8.
If you are installing doors and windows, have the architect check required leakage rates and thermal characteristics of assemblies in Section 5.4.
Lighting control requirements can present a problem if they are not properly understood early in the design stage. Have your lighting designer become familiar with section 9.4, which spells out the requirements for lighting controls and automation systems.
Mandatory provisions of ASHRAE 90.1-2007, Sections 5–10, can be stricter than local codes and should be understood at the beginning of the design phase.
Non-compliance with any of the requirements disqualifies the project from LEED certification. All projects, including remodeling projects, must meet the requirements for all components and systems within the scope of the fit-out. Exemptions include buildings designated “historically significant” by a recognized authority (such as the U.S. Dept. of the Interior), 24-hour facilities, equipment and portions of building systems that use energy primarily to provide for industrial, manufacturing, or commercial processes.
The mandatory provisions (Section x.4) are separate from and in addition to the prescriptive requirements (Sections x.6) of ASHRAE 90.1. The two are commonly but incorrectly used interchangeably. None of the mandatory provisions can be compromised; prescriptive requirements, however, provide a way to meet the minimum efficiency requirements of this prerequisite and offer multiple options for doing so.
In addition to meeting the mandatory requirements, the project must demonstrate that the energy use of the project is equivalent to ASHRAE 90.1-2007. This can be demonstrated by complying with the prescriptive checklist or simulating whole-building energy use with an energy model, also known as the performance option.
The four components of energy use under this prerequisite—envelope, lighting, HVAC and hot water—include only those components that are within the scope of CI work. So, if the hot water boiler is owned by the base building, and the tenant is installing a pipe and pumps to deliver hot water to the bathrooms, the prerequisite covers only the delivery method. So the pipe and the pumps must meet ASHRAE requirements for minimum pipe insulation and pump efficiency—the efficiency of the hot water boiler need not be accounted for.
Developing a simulation model is an added expense and you may need it to provide a demonstrable payback if you’re going to use it as part of your compliance path. It can be well worth the cost, however, especially on larger projects with greater scope. If the scope of the project is larger (>100,000 ft2) and includes a central plant in addition to HVAC distribution and lighting, it can make sense to develop an energy model to assist in system selection and lighting design.
Most CI projects find it cost-effective to pursue the prescriptive option because of a limited design scope in HVAC systems and the building envelope, making the energy model of limited use as a design tool.
Selecting a performance-based approach using an energy model solely for LEED compliance is not recommended. Equal opportunities are available with either the prescriptive or performance approaches for LEED compliance.
Refer to the ASHRAE 90.1-2007 standard for lighting power density allowances. The prerequisite requires your project’s lighting power density (in watts/ft2) to be 10% lower than the standard. ASHRAE lists allowable LPDs in the reference standard of Section 9.5.1 for building types, and in Section 9.6.1 for individual space uses.
Lighting power density is defined as the amount of total lighting power in watts used for a given floor area in ft2 (watts/ft2).
The calculation addresses total lighting power use, although it can be determined in two different ways: the building area method or the space-by-space method. Review the ASHRAE LPD allowances and space-type definitions. Consider which approach is most appropriate for your project to demonstrate compliance.
Refer to EAc1.1: Optimize Energy Performance—Lighting Power for a more detailed description of these methods and credit achievement.
The building area method is simple and it is an easy one for projects that include only a few space types and can be easily classified as one of the building types listed in ASHRAE, Table 9.5.1. The table refers to a single lighting power allowance for each building type. To determine your project’s performance, compare the total allowable LPD for the building type to the installed LPD of your project.
The building area method allows trade-offs to accommodate for increased LPD in specialized spaces. This is done by intentionally reducing LPD in other areas to meet the whole building LPD allowance. The LPD of those specialized spaces may exceed the allowed LPD as long as the whole building LPD is in compliance.
The space-by-space method is a good option for projects that do not fit into one of the building type categories or that require increased LPD allowances for either decorative or merchandise lighting. These types of spaces are allowed higher LPDs, but these increases can only be counted to the extent that they are actually used. ASHRAE allowances are listed in Table 9.6.1 for each space type.
The ASHRAE standard refers to “installed” LPD, so all the light fixtures installed during design and construction must be included in the calculation. Often, designs will provide two fixtures to supplement each other at different times. For example, task lights may be designed to be used only intermittently, but for LPD calculation purposes, you should assume that all lights are switched on.
In a remodeling project, if new lighting is replacing less than 50% of the total installed wattage, the project is exempt from reducing LPD 10% from the ASHRAE 90.1-2007 standard. However, you still must comply with all mandatory requirements for controls and wiring.
Research the exemptions in ASHRAE 90.1-2007, Section 126.96.36.199. Many types of performance and high-powered performance lighting (such theatrical lights) are exempt from the calculations. Refer to the additional lighting allowances for artwork, decorative lighting, and display lighting listed in Section 9.6.2.
LEED only refers to ASHRAE 90.1-2007, Sections 9.4 and 9.5. Other sections are not applicable to LEED certification requirements.
Provide independent controls for all task lights. (This can also contribute to earning EAc1.2: Optimize Energy Performance—Lighting Controls and IEQc6.1: Controllability of Systems—Lighting.
Based on new purchases that are planned, develop a list of appliances and equipment that must meet the Energy Star requirement for your project. If it is Energy Star-labeled, then it must be included in the list. At a minimum, this should include office equipment such as computers, fax machines, printers, scanners, and monitors, as well as appliances such as refrigerators, dishwashers, clothes washers and dryers.
Check the Energy Star website for an up-to-date listing of Energy Star-labeled products and appliances.
HVAC, lighting, and building envelope products are not included for this purpose, because they are addressed in other parts of EAp2 and EAc1.
Refer to credit EAc1.4: Optimize Energy Performance—Equipment and Appliances, for a more detailed description of these methods and credit achievement.
This prerequisite requirement is typically easy to meet. Most office computers and equipment are Energy Star-labeled and usually at little or no cost premium. Carrying out the calculations early on will tell you if the owner should specify more Energy Star-labeled equipment for the new spaces.
Explore opportunities to reduce energy demand by identifying all large, energy-using systems in the project. In a typical office, lighting can contribute 30%–50% of a space’s total energy use, with HVAC at 20%–30%, and the rest for equipment and power loads. If your project’s scope allows envelope modification, explore window size and performance, shading systems, and daylight optimization.
If the owner has identified a percentage reduction in energy-use goals—over code or per square foot—the design team should identify measures to achieve them by optimizing mechanical and lighting design, plug-load equipment, and any other energy-using systems.
Review ASHRAE equipment requirements before system selection as applicable to your project. These are critical and often-overlooked decisions.
Seek synergy in design disciplines. For example, the layout of interior partitions can have an impact on meeting the mandatory provisions for lighting controls.
Decide on your compliance path—Option 1: prescriptive or Option 2: performance—early in the schematic design phase.
Have your mechanical engineer become familiar with all the requirements of the prescriptive sections of ASHRAE 90.1, especially section 6.5. Because this is a prerequisite, noncompliance with any of the provisions disqualifies the project from LEED certification.
Complying with the prescriptive method may require some additional time on the part of the design team to review and update compliance with each requirement. The mechanical engineer, architect, and lighting designer need to walk through the checklist to track the status of each requirement.
Use the ASHRAE compliance forms to update the status of your prerequisite compliance. Typical prescriptive requirements may include a certain heat-pump efficiency rating and the installation of economizers. Building owners may perceive these to be high-cost items, so keep the owner involved in your prescriptive requirement review.
Contract the modeler by the schematic design phase. Have them provide a high-level review of energy-efficiency opportunities, including HVAC system alternatives, lighting power density targets, and proposed envelope assemblies, if applicable.
Develop the lighting layout and identify fixtures so that the design LPD target will be 10% lower than the ASHRAE standard. Use calculation tools and ASHRAE compliance forms to run preliminary lighting power density calculations.
Lighting loads can be reduced through the use of indirect lighting design, lower ambient light levels with increased task lighting, and efficient fixtures such as LEDs, T5 fluorescent lighting, and compact fluorescent lighting.
Use halogen and incandescent lamps with high power density sparingly or not at all, as they can prevent you from meeting the prerequisite.
With early design direction and energy-efficient fixture selection, lighting power density can easily be reduced by 10% with little or no additional cost.
Add the rated power for each piece of new equipment to the list of appliances and equipment that you began during the predesign phase. When the rated power is not easily available from product data sheets, refer to the Energy Star website.
“Rated power” refers to the maximum amount of power that can be drawn by a piece of equipment at any given time. Be sure to use this for each appliance and piece of equipment to be consistent in your documentation.
From your list of appliances and equipment, create a table that includes power rating for each entry, and whether each is Energy Star-labeled. Add the power usage for each piece of equipment on your list, including Energy Star-labeled equipment. The percentage of total power usage from Energy Star-labeled equipment should be at least 50%.
Confirm that the established energy-efficiency measures are incorporated into your design. Identify any questions left open or strategies not included and analyze the potential long-term energy savings before ruling out a strategy that the team or owner is considering eliminating because of its perceived high cost.
Using an integrated design process, the team can easily reduce energy usage below ASHRAE 90.1-2007 thresholds. When designing the lighting layout, the team can take into account the daylighting design of the space in order to reduce the number of fixtures and lower the wattage. The architect can finish the interior space to further enhance lighting efficacy and reduce dependence on mechanical cooling and heating. If appropriate, the mechanical designer should evaluate underfloor air distribution or radiant heat instead of ducted air for higher efficiency.
The mechanical system design often includes the distribution of air and a refrigerated or heated medium. Pumps and fans are large components of energy usage. Use variable-frequency drive pumps and a variable-air-volume distribution system to address fluctuating demand. Install sensors and controls to maintain air volumes and reduce energy waste during low-occupancy periods.
The mechanical team should meet with the base building’s engineer or manager early in the process to get detailed information on the potential to add controls, outside air intakes, and to make efficiency modifications to base building systems.
Continue to verify that the mandatory and minimum requirements of ASHRAE 90.1–2007, Sections 5–10, are being met throughout changes in the design development phase.
Constant communication among project team members throughout the design process is important for minimizing construction and operational costs and meeting the project’s goals. For example, changing a specification, such as the solar heat gain coefficient of glazing, affects mechanical system sizing. These opportunities should be discussed with the team and incorporated into the design.
Continue to verify that the prescriptive requirements of ASHRAE 90.1-2007, Sections 5–10, are being met throughout changes in the design development phase.
All ASHRAE compliance forms should be completed during the design phase to track status and compliance whenever changes are made.
The compliance forms are not required by LEED Online, but it is a good practice to complete them during design development to use as a checklist for the project team and keep them until the project receives LEED certification.
The energy modeler should begin the modeling now, and continue to update it whenever design changes are made to ensure that the project maintains the prerequisite requirements.
Work on an energy model typically takes three to four weeks before it can provide reasonable results and recommendations, so be sure to start this early in design development.
The model is a great design tool that should be utilized to its full potential during design development. Use it to assist in design development for interior mechanical fit-out spaces, comparison of alternative systems, determination of lighting loads, and selection of fixtures. Simulate alternative strategies or designs to provide a true cost-benefit analysis of energy-saving features, along with long-term energy savings and lower maintenance costs for the tenant and building owner.
The energy model can also demonstrate potential savings on the whole building level. While the base building may have existing energy constraints, take the opportunity to encourage future upgrades such as a new central plant, more controls in the base system, end-user ability to set temperatures and reduce energy use, a more efficient air-distribution system—improvements that will benefit the whole building.
The documentation for the performance approach is the same as for EAc1.3: Optimize Energy Performance—HVAC, Option 2 – Energy Cost Reduction, 15-30%.
The prerequisite is dependent on the baseline allowance of lighting watts/ft2. Run preliminary calculations, using the building area method or space-by-space method, and determine which option provides the greater allowance for your project.
If your project develops an energy model, you can use it not only to optimize the lighting design but also to demonstrate that lighting power density is 10% less than the ASHRAE baseline case, per Appendix G.
Check Section 9.6.2 for potential additional allowances for decorative or display lighting. This additional power density is a function of the type of merchandise and the space area.
Although daylight and occupancy sensors help to keep energy costs low, they cannot be used in calculations for lighting power density. However, if your project develops an energy model to demonstrate HVAC and lighting compliance, occupancy and daylight sensors can be used to reduce design-case energy use, per ASHRAE 90.1-2007, Appendix G, Table G3.1, Section 6.
Using the table of appliances and equipment that you developed previously, confirm the rated power of products listed and compliance with the requirement that 50% of the total rated power be Energy Star-labeled.
The calculations are based on the rated power of each appliance or piece of equipment. So a single large power-using appliance, like a refrigerator, may have a higher rated power than dozens of computer monitors. Investigate if those large appliances are Energy Star-labeled, especially if they are to be purchased new for the project, to increase the project’s percentage of rated power that is Energy Star-labeled.
Identify unique or unfamiliar energy-efficiency strategies in the construction documents and confirm expectations and requirements for installation. Outline standards and requirements in bid packages so that they are clear to the general contractor and subcontractors.
Apply for rebates and incentives based on actual system selection.
Revisit all prerequisite requirements to confirm compliance after any value engineering has been completed.
As the prerequisite energy target goes beyond code compliance, some members of the construction team may not be familiar with the additional requirements. Integrate equipment selections in drawings and bid documents.
Refer to the ASHRAE compliance form to check if measures such as controls, sensors, wiring, equipment efficiency, window specifications, and pipe insulation are included in drawings and bid packages.
Discuss efficiency upgrades with the bidding teams to clarify any questions about new systems.
Ensure that the specified lighting system and controls are installed.
Do not replace high-efficiency lighting to reduce costs.
Update the table of appliances and equipment after the construction documents are complete to track any reduction or increase in the amount of Energy Star-labeled equipment and appliances. If the Energy Star-labeled systems do not make up 50% of the total rated power, revisit the list to identify which appliances and equipment can be upgraded to meet the threshold.
Install the systems as specified. Have the mechanical engineer and the commissioning agent visit the site to ensure that the correct systems are being installed.
Confirm that the system components and system efficiency are the same as that specified.
Develop the compliance documentation. Compliance can be demonstrated with ASHRAE 90.1-2007 compliance forms, or the LEED Online form may be signed by the registered architect and design engineer.
Demonstrate compliance using the ASHRAE forms or a sign-off by the registered architect and engineer.
Demonstrate LPD compliance using ASHRAE compliance forms— or if your project developed an energy model, use the outputs from the model to fill in the forms. Compliance forms are available on the ASHRAE website for free download.
ComCheck may be used to demonstrate compliance with LPD requirements.
Complete the table of equipment and appliances in LEED Online and verify that 50% of the rated power is Energy Star-labeled.
Have the MEP engineer and controls contractor develop an operations manual in collaboration with facility management and the commissioning agent to aid in maintaining and correctly operating all energy-efficient equipment.
Energy-efficient design strategies may be new to the users and operating staff. It is helpful to develop training and an O&M manual. Occupants and facility staff should be aware of any automatic controls and refrain from changing settings and controls during the initial months of occupancy.
Energy-efficiency measures often offset their own cost by providing large savings on operational energy bills. These prerequisite requirements are directly tied to the benefit of efficient, low-cost operations.
The lease or sale agreement may include a fixed utility rate such that energy-efficiency measures do not provide a direct payback to the client. In these cases, the tenant or buyer may want to renegotiate the lease with the landlord so that utilities are not included in the agreement and are paid directly by the tenant.
Excerpted from LEED 2009 for Commercial Interiors
To establish the minimum level of energy efficiency for the tenant spaceTenant space is the area within the LEED project boundary. For more information on what can and must be in the LEED project boundary see the Minimum Program Requirements (MPRs) and LEED 2009 MPR Supplemental Guidance. Note: tenant space is the same as project space. systems to reduce environmental and economic impacts associated with excessive energy use.
Design portions of the building as covered by the tenant’s scope of work to comply with ANSI/ASHRAE/IESNA Standard 90.1–2007 (with errata but without addenda1) and complete the following:
Projects in California may use Title 24–2005, Part 6, in place of ANSI/ASHRAE/IESNA Standard 90.1–2007.
Design the systems impacted in the tenant’s scope of work to maximize energy performance. Use a computer simulation model to assess the energy performance and identify the most cost-effective energy 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 local code may be used to satisfy this prerequisite in lieu of 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.
1. Project teams wishing to use ASHRAE approved addenda for the purposes of this credit may do so at their discretion. Addenda must be appliedconsistently across all LEED credits.
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.
Non-profit organization aiming at design community to increase collaboration for designing energy efficient buildings.
International association of energy modelers with various national and local chapters.
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.
Explore this website to find out how building green can boost your bottom line. Get tips for streamlining design and construction. Learn which strategies deliver the biggest paybacks.
Free download of AHSRAE energy savings guide, use for Option 2.
Research warehouse for strategies and case studies of energy efficiency in buildings.
A prescriptive program to achieve signifi cant, predictable energy savings in new commercial buildings.
This website lays out design process for developing an energy efficient building.
An online window selection tool with performance characteristics.
This online resource, supported by Natural Resources Canada, presents energy-efficient technologies, strategies for commercial buildings, and pertinent case studies.
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.
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.
Computer modeling for building energy use.
AIA publication highlighting local and state green building incentives.
2008 guidelines and performance goals from the National Science and Technology Council.
DOE tools for whole building analyses, including energy simulation, load calculation, renewable energy, retrofit analysis and green buildings tools.
This is a tool available to download for envelope moisture analysis tool.
WUFI-ORNL/IBP is a menu-driven PC program which allows realistic calculation of the transient coupled one-dimensional heat and moisture transport in multi-layer building components exposed to natural weather.
Autodesk BIM software facilitates an improved way of working collaboratively, using a model created from coordinated, consistent design information.
The following links take you to the public, informational versions of the dynamic LEED Online forms for each CI-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 restrictions for these forms; for more information, visit LEED Online and click "Sample Forms Download."
Documentation for this credit can be part of a Design Phase submittal.
Complete documentation for achievement of EAp2 on a LEED-CI 2009 project.
Just document the provisions within the project's scope of work. You will need to comply with the prescriptive provisions as well as the mandatory or do a Section 11 model.
we have just certified a building as Core and Shell, but now the owners want to achieve also the Commercial Interior certification. Can i use the Performance Rating Method (eventually updating the model if in the construction fase something changes) or should i follow the Energy Cost Budget method?
Thank you in advance!
Do you meet the prescriptive requirements? If you do that may be the simpler option. If not then the performance option would be necessary. Might want to look through the Interpretations but I do not see why they would not allow you to use an Appendix G model for the purpose of this prerequisite. If it is not addressed in the Interpretations might want to ask GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC). directly.
Projects outside the US may use USGBC approved equivalent standards to show compliance to the Minimum Energy Performance. Is there a list with these standards for Europe and/or The Netherlands?
There are currently no standards approved as equivalent to ASHRAE 90.1-2007. If your teams wishes to pursue this path, guidance on how to do so can be found in the Global ACP supplemental Reference Guide, located here: http://new.usgbc.org/resources/leed-reference-guide-green-building-desig...
If an AHU1.Air-handling units (AHUs) are mechanical indirect heating, ventilating, or air-conditioning systems in which the air is treated or handled by equipment located outside the rooms served, usually at a central location, and conveyed to and from the rooms by a fan and a system of distributing ducts. (NEEB, 1997 edition)
2.A type of heating and/or cooling distribution equipment that channels warm or cool air to different parts of a building. This process of channeling the conditioned air often involves drawing air over heating or cooling coils and forcing it from a central location through ducts or air-handling units. Air-handling units are hidden in the walls or ceilings, where they use steam or hot water to heat, or chilled water to cool the air inside the ductwork. (initially outside of the scope of work) had to be modified in order to comply with the ventilation requirements of Standard 62.1-2007, does it have to comply with the requirements of Standard 90.1-2007, Section 6?
In that case, would it have to comply with all of the points in Section 6, or only with those related to the components of the system that were modified?
Thanks for your help!
We are preparing for an 4800 sq ft office renovation in a portion three story building and would like to pusue LEED-CI.
We will not be touching the HVAC systems; large rooftop units. However we re refitting all the lighting to High efficiency with daylight harvesting.
Are we required to include the HVAC system in our application?
Only the items in the project's scope of work are evaluated in the CI submission.
I am also not totally straight about this. If my tenant is not upgrading the lighting or HVAC, do I need to evaluate it? What about meeting IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors. PR1? If the existing system satisfies code but does not satisfy ASHRAE 62, and the tenant is not going to address it during the fit out, does that mean we can not try for LEED?
I have a few questions regarding Section 9.4.1 Lighting Controls,
1. On page 141 of the LEED Reference Guide for Green Interior Design and Construction (2009 Edition, Updated May 2011), it reads "Buildings larger than 5,000 square feet must have an automatic control device to shut off all lighting in the building". If the office we are certifying is located in a building that does not have an automatic shut-off device, can we claim this section of Standard 90.1-2007 is out of scope? Or do we have to install a shut-off device in the office space we are certifying?
2. I am having troubles determining what spaces in the office need an occupant sensor, as specified by Section 188.8.131.52b. Specifically, about point "6. office spaces up to 250 ft2". What is exactly meant by "office spaces"? Does it refer to any enclosed space in an office with an area of 250 ft2 or less? For example, would a private office of a worker, that has an area of 200 ft2 require an occupant sensor? Because I think this would contradict what is written on page 141 of the LEED Reference Guide for Green Interior Design and Construction (2009 Edition, Updated May 2011) that reads "Shared spaces [...] must be equipped with a control that turns lights off...", since the private office is not a shared space.
3. Lastly, would an open plan office require occupant sensors? It is not mentioned in Section 184.108.40.206b, but I have my doubts.
1. Lighting control is often done on a space-by-space basis. You need to meet the lighting control requirements for the areas in the CI scope, even if the base-building does not.
2. "Does it refer to any enclosed space in an office with an area of 250 ft2 or less?" exceptions are allowed for safety in spaces like mechanical rooms.
I´m still unclear about a couple of things, though:
1. Would I need an automatic shutoff device that shuts off all lighting in the office, if the office is greater than 5000 square feet?
2. Would private offices having an area up to 250 square feet require occupant sensors?
I appreciate your help.
I have another doubt about the Budget Building Design from section 11 of ASHRAE 90.7 – 2007. When you choice of materials for the , Budget Building Design, the Table 11.3.1 says that they should have the same heat capacity from the proposed building but have the U-factor required in Table 5.5 . So, to create the Budget Building Design I'm changing the reference parameters of the proposed building materials in order to maintain their heat capacity and modify only the U-factor. This is a correct procedure to make the building of reference?
Thanks for the attention
Sounds like the way to do it.
I'm simulating a store to the LEED CI cetification and using the section 11 to create the Budget Building Design. But I didn't understand the following paragraph of the note B of table 11.3.2A that says: "Supply air temperature shall be reset based on zone demand from the design temperature difference to a 10°F temperature difference under minimum load conditions. Design airflow rates shall be sized for the reset supply air temperature, i.e., a 10°F temperature difference". Someone can help me how to interpret this note, please.
thanks for the attention
It requires a supply air temperature reset on 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. Reheat systems. At full load, your supply temperature difference in the baseline will be 20˚F (per para 11.3.2.g). At part load it must reset to 10˚F to minimize the need for reheat.
Why are you using ECB instead of Appendix G?
As per EA.p2, one of the requirements to comply with this pre-requisite is to achieve the prescritive requirements (Section 5.5,6.5,7.5 and 9.5) or the performance requirements of Section 11.
If we choose to meet the requirements of Section 11 we should not use appendix G, isn't it correct?
Thank you for your reply, but we are still in doubt in this paragraph. I'll try to describe a numerical example to try to explain this doubt. I have a setpoint of interior temperature of 73.4 º F, and, in accordance with paragraph 11.3.2.g, supply temperature of the ECB should be based on a temperature difference of 20 ° F, i.e.; 53.4º F in our case. We would like to know where the temperature difference of 10 º F, that table 11.3.2A- note b refers, fits.
I'm working on a LEED-CI offices project. I'd like to apply additonnal interior lighting power as specified in ASHRAE 90.1-2004 section 9.6.2b: Lighting to be installed to meet the requirements of visual display terminals. So I assumed that a computer is a visual display and the user needs more lighting for his work. So we are using a T8 luminaires under desk shelf.
To have additional power accepted, the luminaire must meet specific requierements. ASHRAE specify a maximum luminance of 80cd/ft² at 65 degrees. What the ft² refer to? Area of the desk, the floor, the luminaire? It is unclear...
Is your project under LEED ID+C 2009? If so the 2004 version of 90.1 does not apply. The additional lighting you mentioned is not available in the 2007 version of the standard.
My project is in Canada. LEED Canada is a little behind and still refer to ASHRAE 2004, so additional lighting may apply. Do you know this version and what they mean about this luminance?
This requirement is related to glare in the vertical plane. So the square footage is in the vertical plane below the fixture.
I have a question about how modeling a building adjacent to an CI project model.
In my project, I'm modeling a store which is inside an commercial centre which is not under LEED certification.
In the simulation model, should I model this adjacent building, considering that the walls shared by the store and the commercial centre are adiabatic. Should I consider this for the proposed and baseline model?
You typically do not have to model an adjacent building to simulate an adiabatic condition. The software we use allows you to simply model walls/opening as adiabatic.
So, I think it's enough to model these shared walls as adiabatic walls, according to what you said.
So, in this project's context, should I model, in both, proposed and baseline model, this shared walls as adiabatic walls?
I did not say that is how you should model it for CI. I do not know nearly enough about your project and what it is trying to accomplish to comment on how you should model it. All I said is that you can typically simulate an adiabatic condition without having to model an adjacent building.
Hello, We are doing a CI-Retai. It is 5,814.13ft2 bank branch located in a mall. We used the whole builing method and got a review comment indicating that we need to recalculate the installed interior lighting power incluiding the ballast power. We got the ballast technical sheet but we don´t know which factor or how to recalculate the interior lighting power.
Thank you very much.
A project I administered received this comment:
Please provide the ASHRAE/IESNA Standard 90.1-2004 User's Manual, Lighting Compliance Documentation including the task lighting and ballast power consumption.
The electrical engineer responded with this question:
We can include task lighting in the comcheck calculation. However, I was looking for clarification on the ballast power consumption. Where and how would this factor be included?
This was GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC).'s response to the above question:
The wattage of luminaires with permanently installed or remote ballasts should be the operating input wattage of the maximum lamp/ auxiliary combination based on values from the auxiliary manufacturers’ literature or recognized testing laboratories; or it should be the maximum labeled wattage of the luminaire. The project team can also refer to the data provided for common florescent and compact florescent fixtures in the Lighting Reference Section the ASHRAE 90.1-2004 User’s Manual. This information may be entered either in the Comcheck calculation or the ASHRAE/IESNA user’s manual documentation, either is acceptable.
The wattage is the combination of the lamp wattage and the ballast factor. So a 32 watt fluorescent with a BF of 0.9375 yields 30 watts. Conversely a 100 watt metal halide and a BF of 1.1 yields 110 watts. Generally you want to use the combination instead of the maximum labeled wattage.
Our LEED project boundary includes 20,000 RSF in total . And the core building spaces where no alterations is being done are 1500 SF with in the leed project boundary. Do we use 20,000 RSF for Gross SF option or do we use 18,500 RSF (which is lees the building core areas) for calculation purposes?
First post!! Here goes. Regarding complience with section 5.5 of ashrae 90.1 using the prescriptive path. Although not stated directly does the following in section 5.2 apply? - "Prescriptive building envelope option, provided that 1. Vertical fenestration area does not exceed 40% gross wall area for each space conditioning category".
Thus, if a fabric alteration proposed (as part of the client scope) is the installation of full height glazing (exceeeding the 40%) does meeting the section 5.5 requirement then not apply? and if so, I presume this is taken on a space by space basis, so that spaces with less than a 40% ratio must comply?
Two related but separate issues. The 40% glazing applies to the building as a whole so I do not think it impacts a tenant improvement unless perhaps this change puts the whole building over 40%. On a whole building basis you would not meet the prescriptive requirements if the glazing is over 40%. You would then need to show compliance through the performance path in Section 11.
You would need to meet the prescriptive requirements for the new windows, so 5.5 does apply in either case.
In general floor-to-ceiling glass would certainly not be considered a positive green building strategy as it usually increases energy use and is detrimental to thermal comfort and good daylighting.
Appriciate the reply. Just to confirm on which complience path to take - In my case as discribed, if the new glazing contained within the scope for is above 40% for a perticular facade, but the building (which is outside the scope and the LEED boundary) remains under 40%, the path is the prescriptive method? Otherwise, if this brought the entire building over 40%, the section 11 path would have to be taken?
In general, what elements dictate the use of section 11? Is it the case that for any reason, if any section of the relative prescriptive requirements can not be met, this dictates that the section 11 path must now be taken?
If that is the case an accurate energy model (complete, and containing elements likly not within the scope e.g. lighting gain, full fabic specifications) must be created. From a simulation perspective the creation of this full dynamic simulation model seems very onerous and potientially not relative to the scope of works.
In general the two approaches are related to code compliance. The prescriptive approach is basically a checklist - meet all of the prescriptive requirements in each section X.5. One would use the performance approach (Section 11 model) if the project cannot demonstrate compliance with one or more of the prescriptive requirements. In order to be in compliance through the performance path the overall energy cost must be better than the baseline.
So yes if you cannot meet a single prescriptive requirement then the performance path must be followed.
You are certainly correct regarding difficulty level and that is one reason why designers strive to meet the prescriptive requirements instead of ignoring them.
It is not fully clear to me how the 40% prescriptive requirement is applied or enforced in a CI project in either path. This is typically not an issue since the envelope of the building is very rarely changed to the degree that you describe within a CI project scope.
The way that I would approach it - if the whole building is under 40% after the project implementation I would ignore the issue and follow the prescriptive path. If the whole building is already over 40% (or will be over 40% as a result of the project) I would follow the performance path or submit a LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. seeking an exemption from doing so.
I’m working on a Commercial Interior Project following the simulation´s path, in section 11.3.2 item e, says: “Budget Building system listed in table 11.3.2A shall have outdoor air economizers or water economizers, the same as in proposed building, in accordance with section 6.5.1.” therefore I don’t have to simulate any economizer if I don’t have any in my Propose Building Design?
In the same project there is a Server Room, I’m not sure how to simulate its HVAC system. In the appendix G in section G3.1.1, exception b it refers to spaces like server rooms can have an independent HVAC system, however, in chapter 11 there isn’t any section related to Server Rooms. I don’t know if I have to model different HVAC system for the Server Room or include it within the HVAC of the overall project.
Thanks for your advice.
Regarding the economizers that sounds correct.
See 11.3.2(j) which seems to allow the possibility of secondary system types.
Thanks a lot for you advice, I have an aditional question.
In order to meet EAP2 the project has to install ENERGY STAR qualified equipment for 50% (by rated powerRated power is the nameplate power on a piece of equipment. It represents the capacity of the unit and is the maximum that it will draw.) of ENERGY STAR eligible equipment installed as part of the tenant's work. Do the loads of the server room's equipments have to be taken into account in this percentage?. In the project those loads are very High.
Thanks in advance
I think they would be part of the requirement if they are new and covered by Energy Star.
We are working on a CI project which occupies portions of four floors in a University Medical Research Building. The LEED project is being undertaken by a medical research group leasing space within the research building. The whole building is owned by the University.
We considered the LEED project as the area leased by the research group; about 40,000 SF. HOWEVER, there is another 17,000 SF that is considered "limited scope" area, which is NOT being leased by this entity, but through which the HVAC system, which is being re-done, passes. In these spaces, only portions of the HVAC equipment, registers and ceiling system will be replaced.
We would prefer to exclude these "limited scope " spaces, as we have no control over the occupants, their purchases, the existing plumbing facilities that they use, etc
If we go that way, how does the MEP work with the energy model? At this point, the whole area of the full and partial scope is included.
In addition, as the new system is ventilating both the full scope and partial scope areas, would these be covered in the IEQp1/c1/c2?
I assume that we would not consider the partial scope areas for IEQp6.1 & 6.2.
In the 8/13/10 document for Treatment of District or Campus Thermal Energy in LEED V2 & 2009, Appendix A says that District Energy Systems have no effect on any EA section prerequisites or credits. Does this mean we no longer need to follow the 8/13/2010 document?
For CI projects only that is correct.
We are using appendix G for modeling in lieu section 11. Manual (LEED-CI) says we can use appendix G with Table 2. Table 2 refers to Table 11.3.1 of Section 11 where proposed design shall use actual system, in our case this is purchased chilled water. The budget building used Table 11.3.2 for HVAC equipment which is electric. This sets up the problem that the August 13, 2010 document seems to address, moreover, appendix A appears to be incorrect, the DES will have an impact on the calculations. Do you agree with this?
Are you referring to the Advanced Energy Modeling Guide? Table 2? Is this Table 2.1 from the Guide?
For future posts - if you expect complete answers please provide complete questions.
Sorry. The table 2 is from the LEED Reference Guide for Green Interior Design and Construction, EA Credit 1.3 (page 170)
This forum is for EAp2 not EAc1.3. Appendix G is allowed under EAc1.3 but it is not allowed under EAp2 as farFloor-area ratio is the density of nonresidential land use, exclusive of parking, measured as the total nonresidential building floor area divided by the total buildable land area available for nonresidential structures. For example, on a site with 10,000 square feet (930 square meters) of buildable land area, an FAR of 1.0 would be 10,000 square feet (930 square meters) of building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet (1395 square meters), an FAR of 2.0 would be 20,000 square feet (1860 square meters), and an FAR of 0.5 would be 5,000 square feet (465 square meters). as I can tell. Section 11 is used to demonstrate compliance and that is why it must be used for this prerequisite. It is the alternative used to demonstrate compliance if the project cannot meet all of the prescriptive requirements.
See note e under 90.1 Table 11.3.2A. If the proposed has purchased chilled water the budget system does as well. This is the same as Option 1 in the DESDistrict energy system: a central energy conversion plant and transmission and distribution system that provides thermal energy to a group of buildings (e.g., a central cooling plant on a university campus). It does not include central energy systems that provide only electricity. so Appendix A is correct.
We are using heat pumps for domestic water heating. (The water source will be from the campus/district condenser water system.) Can we take credit in the energy calculations using heat pumps? If so, how is this modeled?
Yes you can claim the energy savings. How you model it depends on your software.
We are using the Trace 700.
For more information on how to model it in Trace call them or post a question on the Trace user's Group at onebuilding.org
We are using appendix G for modeling in lieu of section 11. Manual (LEED-CI) says we can use appendix G with Table 2. Table 2 refers to Table 11.3.1 of Section 11 which says the budget building design and proposed building design service hot water systems are to be the same. This seems to contradict the response.
See above regarding source.
Table 2 that I am referring to is from the LEED Reference Guide for Green Interior Design and Construction, EA Credit 1.3 (item 11 on page 171). The Table 11.3.1 is in Section 11 in ASHRAE 90.1-2007.
This forum is for EAp2 not EAc1.3. Appendix G is allowed under EAc1.3 but it is not allowed under EAp2 as farFloor-area ratio is the density of nonresidential land use, exclusive of parking, measured as the total nonresidential building floor area divided by the total buildable land area available for nonresidential structures. For example, on a site with 10,000 square feet (930 square meters) of buildable land area, an FAR of 1.0 would be 10,000 square feet (930 square meters) of building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet (1395 square meters), an FAR of 2.0 would be 20,000 square feet (1860 square meters), and an FAR of 0.5 would be 5,000 square feet (465 square meters). as I can tell. Keeping the hot water energy use the same under EAc1.3 makes sense since the purpose of that Appendix G model is to determine HVAC related savings only. Section 11 is used to demonstrate compliance and that is why it must be used for this prerequisite. It is the alternative used to demonstrate compliance if the project cannot meet all of the prescriptive requirements.
The CI Reference Guide says on page 142 that systems within the project scope of work are eligible for trade off. Assuming the heat pumps you referred to are in the scope of work they are eligible for trade off or savings relative to this prerequisite.
Hi LEEDuser community,
I have read some old posts regarding this issue, but I still want to double check with you guys. I hope you don´t mind. So, the way I see it (correct me if I´m wrong), there are two options in order to comply with this pre-requesite:
A) Comply with BOTH mandatory provisions and prescriptive requirements.
B) Comply with mandatory provisions AND perform a simulation following ECB method in section 11 of ASHRAE Standard 90.1
Now, if that is the case, I´m wondering if my project team should take on a project overseas which aims to obtain LEED CI certification. First of all, the potential tenant is moving to the 5th floor of a builing that does not comply with ASHRAE 90.1 mandatory provisions. I can tell this right off the bat becuase, for instance, air leakage for fenestration and doors has not been determined by an accredited organization such as NFRCNational Fenestration Rating Council (NFRC) is a non-profit organization that provides uniform, independent rating and labeling used to measure and compare energy performance of windows, doors, skylights, and attachment products. [220.127.116.11 mandatory provision - ASHRAE 90.1]. (I even would dare to say that the cfm/ft2 is a bit above the minimum established in some cases)
On the other hand, I read in old posts as well as in the LEED2009 ID + C reference guide(page 139, under "less stringent local code") that since an issue like the one mentioned before is not in the scope of work of the tenant, then s/he is not required to comply with it. Nevertheless, when I see section 11.1.4 of ASHRAE standard 90.1, it basically says that compliance with section 11(ECB method) will be achieved if mandatory provisions are met.
In conclusion, the whole thing seems like a catch-22 to me. However, if that is not the case, how should we proceed?
- What is the "minimum level of energy efficiency for the space systems" that is being referred to in LEED2009 ID + C reference guide(page 139, under "less stringent local code")?
- For this particular project, the HVAC terminal units are in the scope of work of the tenant. So, does it mean that we will comply with this entire pre-requesite as long as we comply with the minimun efficiency requirements in Tables 6.81.A-G (assuming the reduction of 10% lighting power density and the installation of energy star products can be taken care of) ?
-How should we go about doing the simulation? if one is still required? Should we model the whole building as it is? Any tactics, tips, procedures, etc to isolate the tenant spaceTenant space is the area within the LEED project boundary. For more information on what can and must be in the LEED project boundary see the Minimum Program Requirements (MPRs) and LEED 2009 MPR Supplemental Guidance. Note: tenant space is the same as project space. for simulation purposes? what would the baseline building be?
> I know this was a long post, so thank you for the time you spent reading it! :)
> And, thank you in advance for any replies!
You only need to comply with the mandatory provisions associated with the tenant's scope of work.
The "minimum level of energy efficiency for the space systems" is what this prerequisite does by establishing a minimum baseline.
If the terminal units are the only HVAC item in the tenant scope of work then as long as the installation complies with all of section 6.4 the project will comply.
You only need to do a simulation if the project will not comply with one or more of the prescriptive requirements in 90.1 associated with the tenant scope of work. The baseline selection is outlined in Section 11. How to model it is a very difficult question to answer in a forum like this.
Thank you Marcus!
Although, I still haven´t been able to find some useful tips regarding the simulation. (not even on lists.onebuilding.org). So, I wonder if anyone knows of any sort of on-line lectures that deal exclusively with this kind of simulation.
You can only model a part of a building without having to model the whole building. You basically create an adiabatic condition at the interior partition walls, floors and ceiling. How you deal with the HVAC system would depend on whether it is a central plant or not. Exactly how you do it depends on the software.
Some have decent technical support which may be able to help for free. There may be online training depending on the software. There are people who provide one-on-one training for specific software.
What software are you using?
I am currently working on a building whose main function will be for painting and which will contain several large paint booths. Over 90% of the energy expended by the building will be to condition the outside air required for the painting process. The intent is to use energy recovery for the paint booth air-conditioning units. ASHRAE 90.1-2007 section 18.104.22.168 Exception c does not require energy recovery for systems that exhaust paint. My intent is to model the baseline building without energy recovery and the proposed with energy recovery and the subsequent process energy savings would be applied toward satisfying EAp2 and earning points for EAc1.
Does this sound like a reasonable approach? If not, I would like to hear your suggestions. TIA.
You will need to provide an exceptional calculation. The fact that 90.1 does not require energy recovery for a process load does not necessarily mean the baseline is no energy recovery. The baseline should be standard industry practice when building a new facility of this type. It is the responsibility of the project team to make the case that no energy recovery is the standard industry practice in this type of facility.
The selling area of a retail commercial interior project will be a conditioned space located over a parking area whose height is half under sidewalk level and half above it. This happens on 2 of the 4 sides of the place. There will be a also metallic curtain for the parking access. Openings including parking garage access are about 25% of this space. Considering the openings DO NOT have operable windows, should we call this place unconditioned space or should it be considered and treated as exterior?
Sounds like unconditioned space to me. See the definition of unconditioned space in 90.1.
Thanks Marcus for your reply
Checking 90.1 the definition of unconditioned space talks about enclosed space and indicates that parking garages with natural or mechanical ventilation are not considered unconditioned spaces. Also cheking the definition of enclosed space I find that it talks about operable windows that we don't have in this case...
Sorry I meant to say - Sounds like it is not an unconditioned space to me. So it is not a space at all and is considered as the exterior.
We are working in a CI project, in which, by error, the lightning contractor obtained some LED bulbs with a larger wattage than the lightning designer specified wattage. This situation lead to and increase in the project's LPDLighting power density (LPD) is the amount of electric lighting, usually measured in watts per square foot, being used to illuminate a given space., to around 93% of the interior lightning power allowance. In order to mend this situation, the contractor proposed to change the ballast settings in order to permanently dim the luminary output to around 70%. Would this be acceptable in order to comply with the prerrequisite's LPD reduction?
ASHRAE 90.1-2007 states that one should use the maximum luminary wattage, so in principle our situation wouldn't be acceptable. On the other hand, if the ballast is permanently dimmed at 70%, the luminary will never consume more power than the one provided by the ballast, and therefore this 70% power could be considered the maximum luminary wattage.
What do you think about this situation? Any ideas?
If the ballast settings are adjustable then what would prevent it from being adjusted again back up to the maximum setting? Not sure this is really permanent?
In this case it sounds to me like the ballast is the auxiliary referred to in 9.4.1b and the wattage is the maximum of the combination.
Thanks for the answer Marcus. The only thing that would prevent the ballasts from being adjusted once again would be the users (they don't want to readjust since they want to comply and take advantage of the energy savings), but I don't expect this to be a valid argument for ASHRAE or the reviewers. On the other hand, based on 9.1.4b, if I use a ballast that, for example, can provide a maximum of 15W to a 27W bulb, then I could consider the luminary wattage to be 15W instead of 27 W. Would you agree?
I am not a expert on LED lighting so I am not sure how a ballast rated at 15 watts can supply a 27 watt lamp. Does the ballast regulate lamp wattage? If that is possible then 9.1.4b says that the maximum wattage of the combination of the lamp and ballast should be used. So if the maximum wattage of a particular combination is 15 watts then use that.
I am also not an expert, but the lightning contractor told us this is a possibility, although the lightning intensity of the lamp will be lower. Anyhow, thanks once again for your help Marcus, we will analyze which is the best way to fix this situation.
Is the lighting contractor more intersted in making a sale or in complying with 90.1?
If you try to put 27 watts of LEDs thru a 15 watt driver you will most likely burn up the driver. The driver should be sized appropriately for the LEDs being controlled by it. Drivers are often over sized a bit. (30W driver for 27W of LED) As noted it is the combination of lamp and ballast/driver that is used for peak wattage. However much the system uses when 27W of LED are installed. Maybe 28 or 29W. Most people don't know what the driver loss is so they just plug in 27W.
Marcus is correct that the peak possible must be used in the value. Programming the system to dim would not work because it could just as easily be reprogrammed. I have seen manufacturers put requested UL max wattage stickers in can lights before. Say a dimmable can light is rated for 150W A-lamp. Upon request, the manufacturer will put a sticker saying the max lamp the fixture is rated for is only 60W. Same fixture, different UL rating sticker. Then they can count that load at the reduced 60W value.
Bill, thanks for your answer. From what I gather, the contractor is trying to help the project team to find a solution to the problem we have, with at least expenses as possible. Regrettably, after a meeting with the contractor and the project owner, it looks like the only acceptable solution is to change some luminaries (and pay the extra costs) in order to comply with the 90% threshold.
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