• Fixed formatting issues in the Performance Outputs tab
• Corrected calculation within the Service Water Heating tab.
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Many projects in Europe are connected to highly efficient district energy systems. However, the EAp2/EAc1 Option 2 guidance provided in the "Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 - Design & Construction" (DESv2) document is not well-suited for the complex interconnected district energy systems with multiple fuel sources that are common in Europe. Many European countries already make use of the Primary Energy Factor (PEF) as a means of evaluating district energy performance and building energy performance. Is there an alternative compliance path available to document EAp2/EAc1 credit for the district energy system using the Primary Energy Factor in lieu of the DESv2 Option 2 compliance path?
An alternative EAp2/EAc1 compliance path is available to document the energy performance for complex interconnected district energy systems in Europe using the Primary Energy Factor and the greenhouse gas emissions associated with these systems. The Sweden Green Building Council developed an approved method, "Treatment of European District Energy Systems in LEED" (available November 1, 2012), which may be used in lieu of EAp2 Option 2 of the "Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 - Design & Construction" guidance. This compliance path is currently available for projects located in Europe only. Note: The "Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 - Design & Construction" (DESv2) is Optional Guidance for LEED 2009 projects. However, project teams that use the guidance must apply all relevant portions of the guidance. The alternative compliance path outlined in the "Treatment of European District Energy Systems in LEED" may only be used to replace Option 2 of the EAp2/EAc1 Energy Modeling Path defined in the DES v2 guidance. Project teams that opt to use the "Treatment of European District Energy Systems in LEED" method must comply with all other applicable requirements of the DES v2 guidance such as those defined for EA Credit 3, EA Credit 4, EA Credit 5, etc. Applicable Internationally; only for projects located in the Europe region.
Our project is located in California. To pursue Option 1: Whole Building Simulation, is there a methodology for documenting additional energy performance for LEED v4 projects regulated by Title 24-2016?
Additional Percent Savings
NC-Retail (except restaurant/grocery)
CS-Retail (except restaurant/grocery)
CI-Retail (except restaurant/grocery)
Is there an adjusted point scale and minimum point threshold where applicable for LEED v2009 projects using ASHRAE 90.1-2010?
**July 1, 2016 update:This ruling has been revised to address the LEED 2009 minimum point requirement released 4/8/2016.**
Yes, LEED v2009 projects that demonstrate compliance using ASHRAE 90.1-2010 may utilize the adjusted point scale as shown in the Related Resource "ASHRAE 90.1-2010 Adjusted Point Scale for LEED v2009 Projects", subject to the following limitations:
• All mandatory provisions associated with ASHRAE 90.1-2010 (or an approved alternative standard) must be met in order for the project to use this compliance path.
• The ID+C thresholds shown are only relevant for projects using the Alternative Compliance Path described in LEED Interpretation 10412 that replaces the LEED 2009 requirements for EAp2, EAc1.1, EAc1.2, EAc1.3, and EAc1.4 with a Performance compliance path. All other ID&C projects would use the standard points available from EAc1.1 through EAc1.4 to comply with the 4-point minimum requirements.
• The CS 2009 EAp2-c1 ACP (http://www.usgbc.org/resources/cs-2009-eap2-c1-acp) may not be used in conjunction with this ASHRAE 90.1-2010 ACP. The project team must either use ASHRAE 90.1-2007 Appendix G with the CS 2009 EAp2-c1 ACP or use ASHRAE 90.1-2010 Appendix G without the CS 2009 EAp2-c1 ACP.
For projects that register on or after April 8th, 2016 and are subject to the mandatory Optimize Energy Performance point minimum:
If the project complies with all LEED v4 Minimum Energy Performance requirements for the relevant LEED v4 rating system, the project shall be considered to satisfy the LEED 2009 EA Prerequisite: Minimum Energy Performance mandatory minimum EAc1 points requirements (applicable for projects registered on or after April 8th, 2016), regardless of number of points achieved when applying this LEED Interpretation. The points documented under EAc1: Optimize Energy Performance shall be as shown in the ASHRAE 90.1-2010 Adjusted Points Scale for LEED v2009 for projects following the Performance Path, and zero for projects following a Prescriptive path.
This LEED Interpretation pertains to the requirement to limit voltage drop for Energy & Atmosphere Prerequisite 2 for Minimum Energy Performance. The current limit is posing a significant hardship to tall buildings relative to satisfying the mandatory requirements of ASHRAE Standard 90.1-2007 (also applicable in 90.1-2010), referenced in the prerequisite.
Specifically, the requirement in Standard 90.1 to limit voltage drop to not greater that 2% for electrical feeders and 3% for branch circuits (section 8.4.1) has proven to be problematic for large projects which often contain feeders of extended length. By comparison, the National Electric Code does not explicitly regulate voltage drop, but suggests model Code language that limits either electrical feeder or branch circuit voltage drop to 3%, with the combined voltage drop of both feeders and branch circuits when added together not to exceed 5%.
This may appear to be a minor difference, However, when applied to long copper electrical feeders which are present in tall buildings, this absolute constraint from Standard 90.1 on the feeder voltage drop (of 2%) results in a significant increase in the required quantity of copper conductors and associated conduit.
As an example of a higher density regions attempting to resolve this issue, the New York City Electrical Code has adopted the National Electric Code model language as mandatory for all buildings and also included an exception for residential occupancies within buildings to limit electrical feeder voltage drop to 4%, and the combined voltage drop of both feeders and branch circuits to not more than 5%.
This change is in recognition of the inherently short branch circuit lengths in typical NYC apartments, and is based on measured testing results which indicate that voltage drop is often negligible due to the conservative feeder and circuit sizing requirements mandated by other aspects of the Code. Thus, for residential buildings the allowable voltage drop of 4% is twice the allowable voltage drop of 2% as required in 90.1. Depending upon the length and capacity of a particular feeder, this difference can equate to a 3X variance in the required quantity of copper conductors and conduit, with a significant associated cost premium.
The magnitude of the cost premium to satisfy the 90.1 criteria in tall buildings, as compared with New York City Code requirements, can be equal to the total of all of the other cost premiums (hard and soft) associated with achieving LEED certification (at the Silver or Gold level) for a medium to large project in New York City.
In order to resolve this issue, we are proposing an alternate compliance path that we believe would meet the intent of the prerequisite, while at the same time preventing cost prohibitive use of significant amounts of additional copper.
Voltage drop is literally the loss of electrical energy (converted to heat) within a building, therefore regulating voltage drop is no different than regulating the energy efficiency of any electricity consuming device in a building (such as light fixtures or HVAC motors).
Several approaches could be implemented within the LEED rating system to address this disproportionate prescriptive requirement of Standard 90.1. A simple and straight forward approach would be to allow buildings utilizing Appendix G energy modeling as the LEED energy compliance path to include voltage drop as a regulated parameter within both the Energy Cost Budget and Design Energy Cost models. Under this approach, the 90.1 criteria (2% for feeders and 3% for branch circuits) would included in the Energy Cost Budget model, but the Design Energy Cost model would be allowed to include the actual voltage drop that will be implemented in the project design.
This approach would achieve the direct intent of the voltage drop requirement of Standard 90.1 in regulating the energy efficiency of power distribution systems, but through the inherent trade-off methodology of Appendix G would allow projects the flexibility to eliminate a disproportionate cost premium that is otherwise incurred by a prescriptive requirement.
The proposed alternative compliance path for meeting the mandatory requirement of ASHRAE 90.1-2007/2010 Section 8.4, Voltage Drop Limitation, allowing voltage drop as a regulated parameter within the energy models, is not acceptable; however, a simplified alternative compliance path can be approved. As noted in the Formal Inquiry, code requirements and guidelines allow flexibility in meeting voltage drop guidance in feeders and branches as long as the overall voltage drop from service entrance to the worst-case connection is within limits. For the purposes of this prerequisite, the mandatory provision of ASHRAE 90.1-2007/2010 Section 8.4 will be met as long as the total voltage drop does not exceed 5%. Internationally applicable.
Table G3.1.1A lists two possible categories for the building heating source: (1) Fossil fuel, fossil/electric hybrid, & purchased heat; (2) Electric and other. In cases where the proposed building design includes both a natural gas heating source and an electric heating source, when should the heat source in Table G3.1.1A be identified as "Fossil/Electric Hybrid" versus "Electric"?
Clarification is requested regarding when a building heat source in Table G3.1.1A should be identified as "Fossil/Electric Hybrid" versus "Electric". The ASHRAE 90.1-2007 User\'s Manual states that a fossil/electric hybrid source "refers to a system with any combination of fossil and electric heat, and the baseline system for this is a fossil fuel system". Therefore, the heating source for the proposed building would be considered "Fossil Fuel" or "Fossil/Electric Hybrid" if the building uses any fossil fuel source for space heating (including backup heating or preheating), and the baseline building heat source would be fossil fuel.Exception: ASHRAE 90.1 Section G3.1.1 Exception (a) stipulates additional system type(s) for non-predominant conditions (i.e. residential/non-residential or heating source) if those conditions apply to more than 20,000 square feet of conditioned floor area. EXAMPLES OF BASELINE HEATING SOURCE DETERMINATION: The Baseline heat source from Table G3.1.1A for the following Proposed Case system types would be fossil fuel since the proposed system design includes a combination of fossil and electric heat: 1. Variable air volume system with gas furnace preheat and electric reheat2. Packaged terminal heat pumps with outside air tempered by fossil fuel furnace3. Water source heat pumps with fossil fuel boiler4. Ground source heat pumps with backup fossil fuel boiler5. 90,000 square feet is conditioned by a variable air volume system with electric reheat, and 10,000 square feet is conditioned with fossil fuel furnacesThe following buildings would be modeled with an additional system type with a different Baseline heating source in accordance with Section G3.1.1 Exception (a):1. 90,000 square feet is conditioned by a variable air volume system with electric reheat, and 20,000 square feet is conditioned with Packaged DX systems with fossil fuel furnaces. In this case, the 90,000 square feet of area would be modeled with an electric heat source in the Baseline Case (System Type #6 - Packaged VAV with Electric PFP Boxes), and the 20,000 square feet of area would be modeled with a fossil fuel heat source in the Baseline Case (System Type #3 - Packaged Single Zone AC with fossil fuel furnace).2. 50,000 square feet is conditioned by water source heat pumps with a fossil fuel boiler, and 25,000 square feet is conditioned by electric heat pumps. In this case, the 50,000 square feet of area would be modeled with a fossil fuel heat source in the Baseline Case (System Type #5 - Packaged VAV with hot water reheat), and the 25,000 square feet of area would be modeled with an electric heat source in the Baseline Case (System Type #4 - Packaged Single Zone Heat Pump). Applicable internationally.
Clarification is requested regarding whether garage demand control ventilation may be modeled for credit. Garage Ventilation is not addressed by ASHRAE 90.1 – 2007, Appendix G, therefore if savings is claimed it must be modeled as an Exceptional Calculation Measure (ECM). Garage demand control ventilation is increasingly becoming standard practice in newly constructed buildings. In order to take credit for this measure as an ECM, it must be demonstrated that the proposed design goes beyond standard practice.
ECMs must be approved by the Rating Authority. As the Rating Authority for LEED projects, the GBCI will accept an ECM for garage demand control ventilation under the following circumstances:
1) Baseline case shall meet the requirements of ASHRAE 90.1-2010, Section 22.214.171.124.5 Enclosed Parking Garage Ventilation. Baseline fan volume shall be based on the minimum required ASHRAE 62.1 parking ventilation rates of 0.75 cfm / square foot. Baseline system fan power shall be calculated at 0.3 watts per CFM.
2) Proposed case shall reflect the actual design. Evidence shall be provided documenting that demand control ventilation strategies are sufficient to automatically detect contaminant levels of concern in parking garages (for example, Carbon Monoxide, Particulates, VOCs, etc. and NO2) and modulate airflow such that contaminant levels are maintained below specified contaminant concentration as identified in ASHRAE 62.1-2010 Addendum d. Evidence shall also be provided that contaminant sensors are placed in space in an appropriate manner for detection of contaminant in question, included in the building commissioning plan upon installation, and then calibrated yearly following installation.
The contaminants of concern that must be monitored may be limited to CO if a narrative is provided justifying how the controls will also help to limit NO2, VOCs and PM2.5 concentrations. The narrative should address how the parking garage minimum exhaust flow rate and/or the minimum fan run time (if applicable) are maintained, and provide clarification that other contaminant levels are expected to remain low based on that design. Note that NO2 would also be expected to be monitored in garages where more than 20% of the vehicles are anticipated to be diesel-fueled.
Note: though it does not need to be addressed specifically in the narrative, the project team must confirm compliance of all ASHRAE 62.1 mandatory measures, including the measure addressing “Buildings with Attached Parking Garages” requiring limitation of vehicular exhaust into adjacent spaces. .
3) If other activities occur in the garage area, the ventilation for these uses shall be in addition to garage vehicle ventilation.
4) Proposed case shall be modeled such that a minimum air flow of 0.05 cfm/square foot is maintained.
5) A narrative shall describe all Baseline and Proposed case assumptions included for this measure, and the calculation methodology used to determine the projected savings. The narrative and energy savings should be reported separately from the other efficiency measures in the LEED Form.
6) No more than a 75% fan energy savings shall be claimed for this measure.
UPDATED on 01/05/18 for rating system version applicability and in Section (2) to clarify that not all contaminants of concern must be continuously monitored.
The project consists of a consumer products manufacturing facility.The energy intensive manufacturing process exceeds an estimated 90% of the facility\'s total energy load. The Project Client has developed a new manufacturing process which consumes approximately 15% less energy per produced than the previous generation process.The new proprietary process has recently been installed at a similar facility and energy reduction has been demonstrated. Since industrial energy for manufacturing is not covered by ASHRAE 90.1-2007 and the building cannot be accurately modeled using the Appendix G method, project team is seeking to establish and obtain approval of an alternative compliance path.Following the Appendix G procedure would be very challenging because there are so many interacting process and non-process systems. Artificially segregating the systems in the model would not reflect energy consumption patterns accurately. Focusing on non-process components that represent less than 10% of the total energy consumption would not demonstrate the majority of the facility\'s energy savings. Manufacturing process improvements targeted at the other 90% of energy usage have a much greater impact on the entire facility\'s energy consumption. Instead of creating an energy model, baseline and proposed energy consumption will be compared by utilizing an Energy Consumption Index (ECI), which is recognized by the Association of Energy Engineers as an accepted methodology for calculating energy consumption in a manufacturing facility. The Project Client has tabulated historical overall site energy data and production at an existing facility which uses only the previous generation manufacturing platform and is also tabulating data from a site with new generation equipment. The energy data from both of these plants is not sub-metered between process and building loads because there is little economic benefit to meter the small building-only loads. An alternative compliance path will be established using the overall site ECI. Please verify that the following method may be used for determining the entire facility\'s energy cost savings.PROPOSED COMPLIANCE PATH:1. Baseline Building:The existing baseline site
Using the Energy Consumption Index instead of ASHRAE 90.1-2007 Appendix G to determine the annual cost savings of the building is not acceptable. The manufacturing process(es) should be calculated using the Exceptional Calculation methodology. A narrative should describe all Baseline and Proposed case assumptions included for this measure, and the calculation methodology used to determine the project savings. The narrative and energy savings should be reported separately from efficiency measures in the template Section 1.7. Additionally, documentation should be provided to verify that the manufacturing process is not standard practice for a similar newly constructed facility by including a recently published document, a utility incentive program that incentivizes the new process, or by documenting the systems used to perform the same function in other newly constructed facilities. While it is acceptable to use monitored data from a similar facility (constructed within the last five years) to document these exceptional calculation savings using a per product or per pound metric, sufficient information must be provided to document the nature of the efficiency improvements made, and to confirm that the data has been normalized appropriately. Specific product names are not required, and the specific details of the manufacturing process are not required; however, the description of the efficiency improvements to the manufacturing process must be adequate to allow the reviewer to confirm that improvements in energy consumption are tied to improved equipment or controls efficiency, and are not associated with decreases in building square footage, differing project locations, local climate data, quantity of shifts operating per day, etc. Any process energy differences related to local climate or weather (such as refrigeration energy, boiler energy, etc.) should be accounted for in the data normalization process, and the method used for normalizing must be clearly indicated. Ensure the same utility rate is used for the proposed case, baseline case, and exceptional calculation. Additionally, all mandatory requirements of ASHRAE 90.1-2007 must be met."
Our project is subject to ASHRAE Standard 90.1-2013 for code compliance. To pursue Option 1: Whole Building Simulation, is there a methodology for documenting additional energy performance for LEED v4 projects regulated by ASHRAE Standard 90.1-2013?
Yes, projects applying Option 1: Whole Building Simulation, and regulated by ASHRAE Standard 90.1-2013 may document additional energy performance improvement under LEED v4 EA credit Optimize Energy Performance as described below. The Appendix G modeling method must be used for the LEED submission, even if the Energy Cost Budget method is used to document local code compliance.
Projects may calculate the Equivalent ASHRAE 90.1-2010 Performance improvement as:
Equivalent performance Improvement = % better than ASHRAE 90.1-2013 + Additional Percent Savings
Where Additional Percent Savings is shown in Table 1:
Table 1: Additional Percent Savings for ASHRAE 90.1-2013
Project Type1 Additional Percent Savings
NC-Retail (except restaurant/grocery) 5%
NC-Health Care 3%
NC-Restaurant / Grocery 3%
NC-All Other 2%
CS-Retail (except restaurant/grocery) 3%
CS-Health Care 1%
CS-Restaurant / Grocery 2%
CS-All Other 1%
CI-Retail (except restaurant/grocery) 4%
CI-Health Care 2%
CI-Restaurant / Grocery 3%
CI-All Other 2%
1 Mixed use buildings shall use the weighted average Additional Percent Savings based on the gross enclosed floor area associated with each building type. Unfinished spaces not submitted in the CS rating system shall use the CS values. Data center space must always be considered “All Other”.
A centrifugal chiller, manufactured in Brazil, is specified for the project. The chiller is not AHRI certified and there is no laboratory in Brazil that can do this test. Since there is no laboratory in Brazil that can do this test, to comply with section 126.96.36.199 Verification of Equipment Efficiencies of ASHRAE 90.1-2007 Standard, would the equipment fall under option d (if no certification program exists for a covered product, the equipment efficiency ratings shall be supported by data furnished by the manufacturer)? Can this equipment be used in the project?
A supplier’s claims regarding energy efficiency would not be considered sufficient to document compliance with EA Prerequisite 2 (Minimum Energy Performance) and EA Credit 1 (Optimize Energy Performance) for a centrifugal HVAC unit that has not been tested and certified by a 3rd party in accordance with AHRI Standard 550-590. However, if the project team can provide documentation that the efficiency has been tested by a third party using an equivalent standard for HVAC efficiency, this testing would be sufficient in lieu of the AHRI Standard 550-990 testing. Any differences in test conditions and the resulting adjustments to the efficiency values claimed in the energy model would need to be described in the project submittal documentation. Alternatively, the project team may use the supplier’s claims regarding energy efficiency if the commissioning scope of work includes field testing of the equipment efficiency for the range of full- and part-load design conditions under which the building will operate; any adjustments related to altitude, etc. must be accounted for in the commissioning testing. In this case, the energy modeling documentation must include details about the commissioning functional testing method to confirm the performance of the chiller at full and part load operation. If the LEED submittal is provided as a split design / construction phase submittal, and the commissioning agent determines that the equipment efficiency does not meet or exceed the efficiency values claimed by the supplier, the energy documentation must be resubmitted at the construction phase with the values measured by the commissioning agent.
Where the local code does not require vestibules or allows alternatives, can the project team take a penalty for not including vestibules in the design model?
Yes, in locations where the local code does not require vestibules or revolving doors the project team may choose one of the two options below. Additionally, all projects using this method must provide a narrative explaining how infiltration and exfiltration of air through building entries is addressed in the design.
1. Manual subtraction of the energy cost savings associated with vestibules as conservatively estimated by PNNL-20026 “Energy Saving Impact of ASHRAE 90.1 Vestibule Requirements: Modeling of Air Infiltration through Door Openings”. Refer to the Related Resource “Default Deduction for Vestibules” for the specific percentage subtraction required based on project type and climate zone.
2. Provide detailed exceptional calculation method calculations with each step of the calculation clearly described and in alignment with the analysis performed in PNNL-20026, but specific to the project building. Document the additional energy consumption of the project building associated with removing the vestibules from the project. No credit will be given for the use of air curtains when using this approach. A sensitivity analysis related to the number of occupants entering on an hourly basis would need to be justified. The narrative would also need to justify that the simulation software is capable of addressing the conditions required for the calculation. (Software with a well-mixed air assumption would not be able to apply this modeling approach).
***Update 11/9/20: This ruling is now applicable to LEED v4.1 BD+C and ID+C projects.
For buildings with high unregulated energy loads, is it acceptable to show compliance with EA prerequisite: Minimum Energy Performance by considering the unregulated load separately from the ASHRAE 90.1 energy model?
**Updated 7/01/2016 to address the LEED 2009 4-point minimum requirement.
For buildings where unregulated loads account for more than 60% of project energy cost, the following alternative compliance path may be followed:
1. Create an energy model that includes all loads (regulated and unregulated), then remove the unregulated loads from the model through post-processing and demonstrate that the project meets the minimum performance required for EAp2, or the 4-point minimum requirement for projects registered after April 8th, 2016 (e.g. 18% for LEED-NC).
2. Demonstrate that the proposed unregulated loads are 5% more efficient than the industry standard baseline or company average production efficiency using the one of the three ECM approaches outlined below.
3. In addition to the standard documentation required for EAp2, submit calculations showing energy model results with all loads (regulated and unregulated) included and all documentation necessary to demonstrate the 5% process energy improvement.
This alternative compliance path can only be used to demonstrate compliance with the EAp2 Minimum Energy Performance requirement, and in lieu of the four-point minimum requirement for projects registered after April 8th, 2016. Points for EAc1 must be determined with 100% of the unregulated load included in the energy model.
Document ECMs using one of the following three methods:
1. For ECMs listed in the Interpretation database:
- Calculate the annual energy cost savings using the procedure listed in the database
- Enter the calculated savings into section 1.7 of the EAp2 form
- Reference the LEED Interpretation number and upload the required documentation
2. For projects establishing a new baseline technology as the industry standard, submit exceptional calculations and at least one of the following:
- List of three facilities built in the last five years that use the baseline technology
- Current utility incentive programs for new construction that establish the baseline
- Published studies justifying the baseline technology as standard practice
3. For projects with proprietary manufacturing processes, demonstrate that the production process is more efficient than the company’s average production efficiency:
- Identify at least three facilities built in the last five years that manufacture the product
- Calculate the process’ past average Energy Consumption Index (ECI) in units of energy per product manufactured to establish the baseline production efficiency
- Provide the new process’ estimated ECI, anticipated production level, and an explanation of how these numbers were determined
- Calculate the annual production process energy cost savings using the baseline ECI, proposed ECI, and anticipated production level
There is significant confusion, and seemingly contradictory LEED Interpretations on the required methodology for addressing “purchased” on-site renewable energy, and/or purchased biofuel that is not considered on-site renewable energy within the LEED energy model. For renewable fuels meeting the requirements of Addendum 100001081 (November 1, 2011) or other purchased renewable fuels, how should purchased on-site renewable energy be treated in the LEED energy model? How should purchased bio-fuels (meaning it I not fossil fuel but is used in a similar manner to bio-fuel) be treated in the energy model?
For any on-site renewable fuel source that is purchased (such as qualifying wood pellets, etc.), or for biofuels not qualifying as on-site renewable fuel sources that are purchased, the actual energy costs associated with the purchased energy must be modeled in EA Prerequisite 2: Minimum Energy Performance and EA Credit 1: Optimize Energy Performance, and the renewable fuel source may not be modeled as "free", since it is a purchased energy source.
For non-traditional fuel sources (such as wood pellets) that are unregulated within ASHRAE 90.1, use the actual cost of the fuel, and provide documentation to substantiate the cost for the non-traditional fuel source. The same rates are to be used for the baseline and proposed buildings, with the following exception: If the fuel source is available at a discounted cost because it would otherwise be sent to the landfill or similarly disposed of, the project team may use local rates for the fuel for the baseline case and actual rates for the proposed case, as long as documentation is provided substantiating the difference in rates, and substantiating that the fuel source would otherwise be disposed of.
When these non-traditional fuel sources are used for heating the building, the proposed case heating source must be the same as the baseline case for systems using the non-traditional fuel source, and the project team must use fossil fuel efficiencies for the Baseline systems, or provide evidence justifying that the baseline efficiencies represent standard practice for a similar, newly constructed project with the same fuel source.
Updated 8/7/17 for rating system applicability.
We request a ruling regarding building ventilation and its impact on EAp2/EAc1. The question is two-fold: (1) Will USGBC/GBCI allow credit for a design that increases ventilation effectiveness other than Displacement Ventilation (a noted exception for PDV now exists in ASHRAE 62.1-2010), and, (2) will USGBC/GBCI allow credit for reduced ventilation by decoupling the outdoor air from the multi-zone VAV system, which requires increased ventilation rates to ensure the appropriate airflow is reaching all of the zones? Project Design Information:The project is a multi-story office space undergoing a major renovation. In accordance with ASHRAE Standard 90.1-2007 Appendix G, the baseline system is System 8. Ventilation is handled by VAV air handling units, thus requiring multi-zone calculations. Due to elevated terminal heating temperature, zone air distribution effectiveness (Ez) is 0.8.Similarly, the proposed system will employ a VAV system, but with decoupled constant-volume ventilation, thus foregoing multi-zone calculations and reducing outdoor air. Ventilation is room neutral resulting in an Ez of 1.0.Referenced Standards/Guidelines/Research:Ez factors and ventilation rates are determined from ASHRAE Standard 62.1-2007 Tables 6-2 and 6-1, respectively.ASHRAE Standard 90.1-2007 Appendix G Section G.188.8.131.52 Design Airflow Rates states:(D)esign supply airflow rates for the baseline building design shall be based on supply-air-to-room-air temperature difference of 20°F
This exceeds the 15°F limit from Table 6-2. ASHRAE 62.1-2007 User’s Manual (page 6-27) instructs to use the worst case factor, which is the heating Ez of 0.8.
ASHRAE Standard 90.1-2007 Appendix G Section G.184.108.40.206 Ventilation states:
(V)ventilation rates shall be the same for the proposed and baseline building designs.
Reviewing the User’s Manual for this section adds:
(V)ventilation can be a major contributor to building energy consumption, but it is not considered an opportunity for energy savings... (V)ventilation is energy neutral as far as tradeoffs are concerned.
Spare a recent exemption for using PDV to reduce outdoor air rates via an allowable manipulation of Ez, no other exemptions exist. Yet, ASHRAE research recognizes the advantages of decoupling ventilation in its ability to reduce ventilation volume and therefore energy costs. From Jeong, J.W., et. al, ASHRAE Transactions 2003, Volume 109, Part 2:
“All-air [VAV] systems are widely used in many types of buildings, [even though] these common systems have several significant deficiencies. …(T)he multiple spaces method must be used to increase the [OA fraction... This increase… may add significantly to energy consumption and operating cost…
“The challenge of conforming to [ASHRAE Standard 62] in an energy efficient manner can be met with a dedicated outdoor air system (DOAS)… The DOAS provides 100% of the required ventilation air at constant volume”
In addition, EPA’s Technical Report PNNL-18774 (Strategies for 50% Energy Savings in Medium Office Buildings) recognized DOAS as a primary energy savings strategy using the previous research by ASHRAE noted above as support and justification.
It is clear that, as written, the ventilation volumes should be the same in both models. But we respectfully ask the LEED® Reviewer to provide us feedback on whether this makes sense for the current LEED® Rating Systems. It appears the rules are evolving (ex. Displacement Ventilation) as technologies and techniques evolve. And yet full credit for decoupled ventilation systems doesn’t currently exist and therefore may discourage designers and owner from investing in a system that often has higher first cost. We recommend and endorse this investment because of the excellent returns both in terms of dollars saved and carbon emissions reduced. We ask for your ruling to create an exception that allows credit for increased ventilation effectiveness and reduced ventilation rates (compared to multi-zone VAV systems) using a DOAS.
Credit cannot be taken for ventilation effectiveness in systems other than displacement ventilation, such as a dedicated outdoor air unit, using an Ez of 1.0 in the proposed case, with an Ez of 0.8 for the baseline case (VAV system).Addendum bj to ASHRAE 90.1-2007 states that the Baseline Case ventilation airflow rates can be calculated using an Ez value of 1.0 only if the Proposed Case Ez value is greater than 1.0. The project team may not take credit unless the Proposed Case Ez value is greater than 1.0, because 90.1 does not set a Baseline Case standard for that scenario. Equivalent to ASHRAE 90.1 may be used.
What is considered “hybrid” heating?
**Update 1.11.2019: LI is applicable to LEED v4 projects.
Clarification is requested regarding when a building heat source in Table G3.1.1A should be identified as "Fossil/Electric Hybrid" versus "Electric".
The ASHRAE 90.1-2007 User's Manual states that a fossil/electric hybrid source "refers to a system with any combination of fossil and electric heat, and the baseline system for this is a fossil fuel system". Therefore, the predominant heating type for the building shall be determined based on the percentage of building area served by Electric-only heating versus “Fossil Fuel” and/or “Fossil/Electric Hybrid” heating. The heating source for any building space would be considered “Fossil Fuel/Electric Hybrid” if the space is heated by any combination of fossil fuel and electricity. This includes backup heating, heating of ventilation air serving the space, or preheating, But does not include emergency backup heat sources. The predominant heating type for the building shall be determined based on the percentage of building area served by Electric-only heating versus “Fossil Fuel” and/or “Fossil/Electric Hybrid” heating. (Note: Emergency back-up heating refers to heating that runs when the primary system fails or needs to be shut off in an emergency, and does not refer to a backup system which may be used to provide additional capacity as needed.)
Exception: ASHRAE 90.1 Section G3.1.1 Exception (a) stipulates additional system type(s) for non-predominant conditions (i.e. residential/non-residential or heating source) if those conditions apply to more than 20,000 square feet of conditioned floor area.
EXAMPLES OF BASELINE HEATING SOURCE DETERMINATION:
The Baseline heat source from Table G3.1.1A for the following Proposed Case system types would be fossil fuel since the proposed system design includes a combination of fossil and electric heat serving the same space for the majority of the building:
1. Variable air volume system with gas furnace preheat and electric reheat
2. Packaged terminal heat pumps with outside air tempered by fossil fuel furnace
3. Water source heat pumps with fossil fuel boiler
4. Ground source heat pumps with backup fossil fuel boiler
5. Residential condominium units with packaged terminal heat pumps, that have any amount of ventilation air provided to the space from air handling unit(s) where the supply air is tempered with fossil fuel.
The following buildings would be modeled with an electric heat source for the Baseline Case since the heating source serving the majority of spaces is electric-only:
1. 90,000 square feet is conditioned by a variable air volume system with electric reheat, and 10,000 square feet is conditioned with fossil fuel furnaces
2. 50,000 square feet is conditioned by electric heat pump systems. 15,000 square feet is conditioned with fossil fuel radiant heaters.
The following buildings would be modeled with an additional system type with a different Baseline heating source in accordance with Section G3.1.1 Exception (a):
1. 90,000 square feet is conditioned by a variable air volume system with electric reheat, and 20,000 square feet is conditioned with Packaged DX systems with fossil fuel furnaces. In this case, the 90,000 square feet of area would be modeled with an electric heat source in the Baseline Case (System Type #6 - Packaged VAV with Electric PFP Boxes), and the 20,000 square feet of area would be modeled with a fossil fuel heat source in the Baseline Case (System Type #3 - Packaged Single Zone AC with fossil fuel furnace).
2. 50,000 square feet is conditioned by water source heat pumps with a fossil fuel boiler, and 25,000 square feet is conditioned by electric heat pumps. In this case, the 50,000 square feet of area would be modeled with a fossil fuel heat source in the Baseline Case (System Type #5 - Packaged VAV with hot water reheat), and the 25,000 square feet of area would be modeled with an electric heat source in the Baseline Case (System Type #4 - Packaged Single Zone Heat Pump).
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