EQc7.1 requires that HVAC designs meet the requirements of ASHRAE Standard 55-2004, which deals with thermal comfort of building occupants. Specifically, ASHRAE 55 requires project teams to address air temperature, radiant temperature, humidity, and air speed. Earning this credit also sets the stage for you to earn EQc7.2: Thermal Comfort—Verification.
In most cases, designing a system that complies with ASHRAE-55 is standard practice and documentation is the only LEED-specific requirement for achieving the credit, so it should cost very little to earn.
Meeting this credit in naturally ventilated spaces is tricky, because it’s hard to ensure that thermal conditions remain within the requisite range. It’s really only possible in a few specific climatic regions with especially temperate conditions.
Certain spaces, such as greenhouses, gymnasiums, warehouses or manufacturing facilities often operate outside of the ranges defined by ASHRAE-55, which can put the project in conflict with designing either mechanical and passive systems that meet the credit requirements. If you have these spaces in your project, check with the USGBC and review past CIRs to determine whether you can earn the credit through an alternative compliance path.
Regardless of the project type, considering target thermal comfort conditions—and designing to meet those conditions—early in the process is very helpful.
The mechanical engineer and architect review ASHRAE-55 along with the credit requirements in the context of the project. ASHRAE-55 requires that you establish a comfort zone based on several variables that affect occupant comfort, and design mechanical systems to create thermal conditions within the comfort zone in each occupied space. Comfort zone calculations are based on the following variables:
Identify any unique programming or climate conditions that might make it tricky to get the credit. Fitness rooms, gyms, natatoriums, or very humid climates often create conditions that require special consideration.
Consider whether mechanical or natural ventilation will be used. When considering natural ventilation systems, review ASHRAE-55 section 5.3 for a description of the relevant requirements.
Include credit requirements in the Owner's Project Requirements for the commissioning credits EAp1 and EAc3.
Consider design implications of credit requirements early in program development. For example, if you are in a humid climate you may need additional dehumidification, which will affect your mechanical space requirements.
Consider how credit requirements will affect energy use and occupant experience, and whether programming is consistent with this credit. This credit is particularly worthwhile for any indoor environment in which occupant productivity is of key importance, and where occupants will benefit from optimized indoor thermal conditions.
Consider pursuing EQc7.2: Thermal Comfort—Verification in combination with this credit. EQc7.2 requires an occupant comfort survey after occupancy.
This credit is generally a low- or no-cost credit. When it does add significant costs, that’s usually because it wasn’t considered early enough, so more equipment has to be added to provide, for example, additional dehumidification. An added cost like that could be prevented by designing the right system early in the schematic design.
In climates where either heating or cooling predominate, or in very humid climates, meeting ASHRAE-55 year-round might require additional system components. For example, spaces that may not otherwise be cooled—like gymnasiums—may need dehumidification or cooling systems to meet the ASHRAE-55 comfort criteria year-round.
It is always important to consider building orientation, the heat-island effect, insulation levels and other design considerations that will have a direct effect on thermal conditions and on the energy consumed to achieve those conditions, but these are not variables that are used as inputs for establishing a thermal comfort zone in ASHRAE-55, so they don’t directly affect whether or not you achieve this credit.
Review how building systems might contribute to or hinder achievement of this credit and review site-specific conditions that will affect building conditioning.
Determine which HVAC system types (mechanical, mixed mode, or natural) and system components can best meet the credit requirements and review any special programming requirements for ventilation, humidity and thermal conditions. For example, consider whether in-floor radiant heating is preferable to forced-air systems and which are best suited to a project’s programming and budget, and confirm that the system will be capable of operating within the established comfort zone.
When beginning to consider thermal conditioning systems, review which system types will not only meet credit requirements, but will balance performance, efficiency and cost while creating an optimal thermal environment in the given climatic region. In some regions, direct evaporative cooling may be an appropriate option, while in others dehumidification may be needed to meet the credit requirements. Review the feasibility of natural ventilation systems versus mechanical systems and consider their effect on energy use, programming, and credit achievement.
Review ASHRAE-55 section 6.1.1 to understand the credit documentation requirements. Assess these inputs:
Review how thermal controls and operable windows affect credit requirements. Projects in very temperate climates may meet the credit requirements through the use of operable windows exclusively, as long as mean monthly outdoor temperatures are between 50°F–92°F. See ASHRAE-55 section 5.3 for details.
Include credit-related information in the Basis of Design for the commissioning credits EAp1 and EAc3. At a minimum this should include:
Don’t assume that projects in Southwestern or other dry climates will automatically meet the humidity requirements of ASHRAE-55. These climates may have a significant number of days in which operating conditions will exceed the ASHRAE-55 requirements for humidity. Refer to the National Climatic Data Center for regional weather data (see Resources).
Natural ventilation designs are more significantly affected by climate and weather than mechanical systems. Although the methodology and inputs for documenting compliance are the same as for mechanical systems, in certain regions project teams using passive systems may have difficulty meeting ASHRAE-55 due to program constraints or seasonal temperatures that are outside of the prescribed range of 50°F–92°F.
Provide occupant controls for each individual space and avoid trying to normalize conditions in large areas or zones of a building. Separate controls will make it easier to achieve the credit in all spaces and improve occupant comfort while reducing unneeded energy use. For example, if there are ten adjacent offices, provide controls for each office separately. This strategy can also help you earn EQc6.2: Controllability of Systems—Thermal Comfort. Added controls may increase upfront costs, but reduced energy consumption should help offset those costs.
Examine operating conditions to confirm how likely you are to meet the credit requirements.
Pick the best calculation method for demonstrating credit achievement. Document EQc7.1 using a Predicted Mean Vote/Predicted Percentage of Dissatisfied (PMV/PPD) calculation, ASHRAE comfort tool, or a psychrometric comfort zone chart from ASHRAE-55. The method you pick will likely be determined by the preference and past experience of the mechanical engineer. (See the Resources tab for software options).
Include the following information on the LEED Online submittal template:
Consider providing additional information about any of the variables that effected your calculations, including:
Make design adjustments to meet credit requirements during design development, keeping in mind the potential impacts on energy use.
Make sure that HVAC engineers track and reconfirm credit-compliant operating ranges through the design development phase.
Make sure that the Basis of Design for commissioning reflects compliance with credit requirements and includes design assumptions and load calculations.
Provide ample thermal controls for building occupants. This will increase comfort and occupant satisfaction and will keep operating conditions within the prescribed ranges of ASHRAE-55.
Occupant access to thermal controls can help to meet the credit requirements on a space-by-space basis while increasing energy efficiency (by preventing conditioning of a whole HVAC zone rather than individual spaces) and increasing occupant satisfaction by giving people greater control over their thermal conditions. Increasing occupant satisfaction will help projects that are attempting IEQc7.2.
Variables like clothing levels and metabolic rates are not compliant or non-compliant, but are used instead to determine what appropriate operating ranges will be for a space. You have to show that your HVAC systems will create conditions within these operating ranges.
Confirm required calculations based on the finalized design by using a PMV/PPD calculation, the ASHRAE comfort tool, or psychrometric zone chart.
Complete all required LEED documentation and upload to LEED Online:
Include ASHRAE-55 related performance requirements in the construction specifications.
Provide LEED documentation requirements in the specifications, including the LEED requirements for information contained in O&M manuals and designating the contractor as the signatory for this credit.
Include LEED references in the drawings and specifications where appropriate.
As a best practice, ensure that O&M manuals include the following:
Have the commissioning agent review the OPR and BOD and confirm that system design and installation will meet the credit requirements for operating ranges.
Set up building operations training to ensure that on-going operation of HVAC systems will meet ASHRAE-55.
Encourage general contractors and mechanical contractors, commissioning agents and building operators to review O&M materials and maintenance procedures together to confirm that system performance and maintenance meets the original design intent.
Set up training with O&M staff on proper operating procedures.
Excerpted from LEED for New Construction and Major Renovations Version 2.2
Provide a comfortable thermal environment that supports the productivity and well-being of building occupants.
Design HVAC systems and the building envelope to meet the requirements of ASHRAE Standard 55-2004, Thermal Comfort Conditions for Human Occupancy. Demonstrate design compliance in accordance with the Section 6.1.1 Documentation.
Establish comfort criteriaComfort criteria are specific design conditions that take into account temperature, humidity, air speed, outdoor temperature, outdoor humidity, seasonal clothing, and expected activity. (ASHRAE 552004) per ASHRAE Standard 55-2004 that support the desired quality and occupant satisfac- tion with building performance. Design building envelope and systems with the capability to deliver performance to the comfort criteria under expected environmental and use conditions. Evaluate air temperature, radiant temperature, air speed, and relative humidity in an integrated fashion and coordinate these criteria with EQ Prerequisite 1, EQ Credit 1, and EQ Credit 2.
This ASHRAE standard defines the criteria for human comfort that is followed to design mechanical systems.
Information about the ASHRAE Thermal Comfort tool with ordering information.
Information about how to use psychrometric charts.
Download free psychrometric chart software.
Free, easy-to-use program from UCLA that displays climate data in the form of psychrometric charts, among others.
The National Climatic Data Center provides regional weather data that you can use to assess your climate relative to ASHRAE-55 requirements.
This spreadsheet categories dozens of specific space types according to how they should be applied under various IEQ credits. This document is essential if you have questions about how various unique space types should be treated.
This template is the flattened, public version of the dynamic template for this credit that is used within LEED-Online v2 by registered project teams. This and other public versions of LEED credit templates come from the USGBC website, and are posted on LEEDuser with USGBC's permission. You'll need to fill out the live version of this template on LEED Online to document this credit.
Documentation for this credit can be part of a Design Phase submittal.
These sample documents, from a LEED for Schools 2009 project in Mass., demonstrate how to document that the project meets the thermal comfort design requirements of ASHRAE 55. LEEDuser thanks Christopher Schaffner of The Green Engineer for providing this sample.
Can anyone tell me what the acceptable values for PMV and PPD are? We received a comment whereby the reviewer noted that the PMV and PPD are outside the accetable thermal environment for general comfort.
Per what I have read it looks like the PPD should be under 10%? but I could not find any reference to what the PMV should be?
You are correct. PPD must be less than 10%
-0.5 < PMV < 0.5
I have a Fire-Station project, where I have a mix of BayA bay is a component of a standard, rectilinear building design. It is the open area defined by a building element such as columns or a window. Typically, there are multiple identical bays in succession.-work space: trucks and vehicles, Residential Area: dorms, showers, dinning, kitchen, living room. Office space: Office, command center & Classroom area.
Does the residential area apply for this credit?
what about the the vehicle area where the tool/shop is located?
I cannot find a good PMV for 0.7 MET 0.96 clo not even at 1 fpm. any insight?
In general , when we have to made measurements? , like air temperature,air speed or globe temperature in the spaces that will be certificated? because it affects in the HVAC design and the schedule of the project.
Lorena, I'm sorry but I'm not sure I understand your question. This credit is based on design, not measurements of a completed space.
We were denied this credit in a residential application recently although our approach has previously been acceptable on similar projects. The review language includes,
"Specifically, the preliminary review comments requested documentation confirming that the system was capable of meeting the humidity setpointsSetpoints are normal operating ranges for building systems and indoor environmental quality. When the building systems are outside of their normal operating range, action is taken by the building operator or automation system., and providing the peak heating and cooling loads when the windows were open to 4% of the floor area during peak heating and cooling conditions. However, the documentation shows an infiltration rate of only 0.35 Air Changes per Hour, which does not appear to represent the level of infiltration anticipated to occur during peak heating and cooling when a window area corresponding to 4% of the floor area is open."
Our team provided documentation verifying humidity setpoints were met, but we are particularly concerned that we need to demonstrate that our system is capable of dehumidification, heating and cooling with all windows open. Has anyone run into this review issue before? Is there any suggested guidance?
You are stuck. You can't have it both ways. If you are using the windows for ventilation, you need to include the effect of the window in the comfort analysis.
In reality you have a building that can provide either comfort or ventilation, but not both, under many conditions. LEED is not going to reward you for that.
How can you achieve compliance with Ashrae 55 with occupants having activitties outside of of the range in the graphics method section 126.96.36.199.
This for an exercise rooms with metabolic rates from 3.0 to 4.0?
Since no response has been posted, I'll chime in.
You should look at the proposed activity levels over a period of time including cool-down periods and rest breaks. If the time weighted average of the various metabolic rates is below 2.0 met,the predicted mean vote (PMV) method in Section 188.8.131.52 may be used.
In general, spaces with high met rates are not covered by ASHRAE 55. For your LEED submission, explain that, and provide a narrative describing how comfort is being addressed in the space.
Our v2.2 multi-family project has standard split system mechanical units, with operable windows. We documented compliance with ASHRAE 55-2004 and received the following comment:
"Please provide a description of the system’s ability to maintain the maximum humidity levels during periods of low cooling load or a justification for no dehumidification strategy based on the local climate conditions."
As the project is located in DC, it's technically possible to have humid days when no cooling is required (so the mechanical units will not operate). However, this is the first time we've encounted this comment. Adding humidistats to the units is very expensive. Any thoughts on how to respond?
Controlling humidity loads at part load conditions is one of the key goals this credit tries to accomplish, so the reviewer is correct to ask for more details.
You need to show how the building maintains comfort conditions year round, not just at design conditions.
Generally we show psychometric charts of cooling coil operation at part load conditions, demonstrating that appropriate space conditions can be maintained. For package equipment with high outdoor air loads in humid climates it may be difficult to meet these requirements.
What does the design air speed refer to?
You'll need to look at ASHRAE 55-2004, but in general it's the velocity of the air (from the supply diffusersIn an HVAC context, diffusers disperse heating, cooling, or ventilation air as it enters a room, ideally preventing uncomfortable direct currents and in many cases, reducing energy costs and improving indoor air quality (IAQ). In light fixtures, diffusers filter and disperse light.) to which a person is exposed.
So that would be roughly 50 fpm based upon the manufacturer's data and ASHRAE? Or how is that determined?
Yes, manufacturer's data, ASHRAE, modeling, could all help you determine this value.
For years I have seen this credit documented without any issues. Recently the reviewer asked for the following supplemental information:
"Please provide a narrative that describes the design strategies used to deal with discomfort from drafts and radiant temperature and the calculations used to determine the comfort zone including clothing allowance and activity level."
We believe we are meeting the credit requirements with the initial documentation provided but are a bit unclear about how to respond to this request. Additionally, achievement of EQc7.2 is dependent on first meeting EQc7.1, so we want to ensure we meet.
Has anyone experienced this type of comment? Any feedback and/or guidance is most appreciated.
I too recently received a similar comment. The comment received on our project was "Please document the comfort parameters used in the calculation of design temperatures, including clothing, metabolic rate, and indoor air speed." Comment goes on to request supporting calculations and description of any local discomfort affects that may be present. Our team was caught off guard by this and we feel we meet the intent. I'm preparing my re-submittal, so if anyone has any guidance I would appreciate it too!
Carlie - I just read through all the info on this website (including the Resourses section) and it was very helpful. Sounds like they want results of calculations that determine the comfort range and the assumptions used in the calculations. We can't simply assume since we fall into the chart in ASHRAE 55 (75F/50% RH in the summer, for instance) that we meet the credit.
I have the very same comment on a Leed for Schools 2007 project. Can you tell me how you addressed this comment...and if it worked?
We just received a very similar comment, what we think is the best approach to solve it is to do a thermal comfort analysis, some energy modeling software include it, such as EnergyPlus, you can choose different models to do the analysis, such as: Fanger, Pierce, KSU and ASHRAE55AdaptiveComfort Model, the one explained in Appendix D of Ashrae 55.1 2004. All of these models give you PMV and PDD values, and since you perform an annual simulation, you can determine very well the thermal comfort levels for each thermal zone.
I have a warehouse bldg. w/ internal offices. I am conditioning the offices but only ventilating the warehouse area & am unclear about documenting my compliance.
For the warehouse, I will review the CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide's.
For the office spaces: is it sufficient to merely use the graph (ASHRAE Std 55-2004, Figure 184.108.40.206)? Pposting your calculated space conditions can indicate that you are within the acceptable range & do comply.
Documenting this credit is a bit more complicated than just checking that one graph. We have step-by-step suggestions in the Checklists tab, above.
This brief guide introduces some of the key variables involved in designing for thermal comfort.
Principal & Founder
The Green Engineer, LLP
Ongoing measurement and verification of mechanical systems will confirm that systems are operating as designed and at levels that maximize efficiency and occupant comfort.
Commissioning will help confirm that equipment set points and operating ranges will create system performance that is consistent with the design intent.
Providing thermal comfort controls will help occupants be comfortable on a space-by-space basis.
Teams must achieve EQc7.1 in order to earn EQc7.2. EQc7.2 offers an opportunity to confirm that the system design and ASHRAE-55 requirements are working to deliver occupant comfort.
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