Schools-2009 IEQc7.1: Thermal Comfort—Design

  • Schools_IEQc7-1_Type3_ThermalComfortDesign Diagram

  • Documenting standard practice

    IEQc7.1 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 IEQc7.2: 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.

  • Natural ventilation and certain occupancies make it tricky

    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 or gymnasiums 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 GBCI on 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. 

    Design submittal? Not really.

    Even though credit is technically a design submittal, it’s tricky to document it before the end of construction because it calls for the transfer of O&M manuals during project close-out with credit-specific information includedt, and because contractors are listed as required signatories. Most of the information, however, can be documented during design by the mechanical engineer. 

    While the credit requirements, and the referenced ASHRAE standard, have not changed from older versions of LEED, the documentation requirements for the credit are now more stringent. Completing the new LEED Online credit form requires greater attention to detail and more supporting calculations, which set a higher bar for coordination among team members.  

Legend

  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip

Pre-Design

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  • 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:

    • Metabolic rate
    • Clothing insulation level
    • Air temperature
    • Radiant temperature
    • Air speed
    • Humidity

     

  • 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.

  • For schools with indoor swimming pools, the natatorium (swimming pool area) must meet the requirements of the ASHRAE HVAC Applications Handbook, 2003 edition, Chapter 4 (Places of Assembly), Typical Natatorium Design Conditions. Purchase a copy of the Handbook and review the requirements. Relative humidity levels of 40%–60% have to be maintained; 50% is optimal. 

  • 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 IEQc7.2: Thermal Comfort—Verification in combination with this credit. IEQc7.2 requires an occupant comfort survey after occupancy. 

  • In order to achieve IEQc7.2, you have to achieve IEQc7.1.

  • 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.

Schematic Design

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  • 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:

    • Weather design conditions for peak load
    • Hours per typical year that outdoor temperatures exceed design conditions
    • Maximum design humidity
    • Design air speed
    • Radiant temperature asymmetry (refers to the changes in personal temperature around the body as affected by differences in nearby surface temperatures, such as heated floors and cold windows)
    • Vertical air temperature difference
    • Floor surface temperature
    • Drafts

  • 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:

    • that you require compliance with this credit;
    • that you require compliance with ASHRAE-55;
    • and what operating ranges should be maintained.

  • 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 IEQc6.2: Controllability of Systems—Thermal Comfort. Added controls may increase upfront costs, but reduced energy consumption should help offset those costs.

Design Development

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  • Examine operating conditions to confirm how likely you are to meet the credit requirements.

  • Pick the best calculation method for demonstrating credit achievement. Document IEQc7.1 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 inputs on the LEED Online credit form:

    • Clothing Insulation and Metabolic Rate of building occupants
    • Weather design conditions used for peak load calculations
    • Hours per year that outdoor temperatures exceed design conditions
    • Maximum Design Humidity
    • Design Air Speed
    • Radiant temperature asymmetry
    • Vertical air temperature difference
    • Floor surface temperature
    • Draft.

  • 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. 

Construction Documents

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  • 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:

    • ASHRAE 6.1.1 documentation
    • IEQc7.1 requirements stated in the OPR and BOD
    • Thermal comfort variables and established comfort zone
    • Calculation results (dependent on chosen methodology)
    • O&M materials (as they are available).

     

  • 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. 

  • Make sure that contractor-related LEED documentation requirements and activities are in the specifications so that they are accounted for in estimates and bids.

  • You might want to defer documenting this credit until the construction submittal to confirm the appropriate system installation and inclusion of the required O&M information.

Construction

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  • Develop the Systems Manual, O&M manual, or equivalent. Ensure that the O&M manual includes the following:

    • General and specific instructions on the maintenance and operation of controls
    • Seasonal settings and changeovers
    • Limits in the adjustment of manual controls
    • Maintenance and inspection schedule for all thermal and other environmental and thermal condition-related building systems.

  • The contractor is the signatory for this credit, and has to confirm compliance with the bullets above and sign off on this credit. 

  • Be certain that the commissioning agent reviews the OPR and BOD and confirms that system design and installation will meet the credit requirements for operating ranges. 

Operations & Maintenance

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  • Set up building operations training to ensure that on-going operation of HVAC systems will meet ASHRAE-55, using the O&M manual for reference.

  • 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.

  • USGBC

    Excerpted from LEED 2009 for Schools New Construction and Major Renovations

    COPYRIGHT © 2009 BY THE U.S. GREEN BUILDING COUNCIL, INC. ALL RIGHTS RESERVED

    IEQ Credit 7.1: Thermal comfort - design

    1 Point

    Intent

    To provide a comfortable thermal environment that promotes occupant productivity and well-being.

    Requirements

    Design heating, ventilating and air conditioning (HVAC) systems and the building envelope to meet the requirements of one of the options below:

    Option 1. ASHRAE standard 55-2004 or non-U.S. equivalent

    Meet the requirements of ASHRAE Standard 55-2004, Thermal Comfort Conditions for Human Occupancy (with errata but without addenda1). Demonstrate design compliance in accordance with the Section 6.1.1 documentation. Projects outside the U.S. may use a local equivalent to ASHRAE Standard 55-2004 Thermal Comfort Conditions for Human Occupancy Section 6.1.1.

    Option 2. ISO 7730: 2005 & CEN standard EN 15251: 2007

    Projects outside the U.S. may earn this credit by designing heating, ventilating and air conditioning (HVAC) systems and the building envelope to meet the requirements of International Organization for Standardization (ISO) 7730: 2005 Ergonomics of the thermal environment, Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal 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 55–2004); and CEN Standard EN 15251: 2007, Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics.

    For natatoriums, demonstrate compliance with the “Typical Natatorium Design Conditions” defined in Chapter 4 (Places of Assembly) of the ASHRAE HVAC Applications Handbook, 2003 edition (with errata but without addenda 1).

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

    Potential Technologies & Strategies

    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 55–2004) according to ASHRAE Standard 55-2004 (with errata but without addenda1) that support the desired quality and occupant satisfaction with building performance. In gymnasiums, if mechanical ventilation is not used, follow ASHRAE Standard 55-2004 (with errata but without addenda1) requirements for naturally ventilated spaces. Design building envelope and systems with the capability to meet 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 IEQ Prerequisite 1: Minimum Indoor Air Quality Performance, IEQ Credit 1: Outdoor Air Delivery Monitoring, and IEQ Credit 2: Increased Ventilation.

Organizations

ASHRAE 55-2004

This ASHRAE standard defines the criteria for human comfort that is followed to design mechanical systems.

U.S. Department of Energy, EERE - Building Energy Software Tools Directory

Information about the ASHRAE Thermal Comfort tool with ordering information.  

University of Nebraska, Lincoln

Information about how to use psychrometric charts.

Software Tools

Trane

Download free psychrometric chart software.

Climate Consultant

Free, easy-to-use program from UCLA that displays climate data in the form of psychrometric charts, among others.

Publications

National Climatic Data Center

The National Climatic Data Center provides regional weather data that you can use to assess your climate relative to ASHRAE-55 requirements.

Technical Guides

IEQ Space Matrix

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.

Thermal Comfort Documentation

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.

LEED Online Forms: Schools-2009 IEQ

The following links take you to the public, informational versions of the dynamic LEED Online forms for each Schools-2009 IEQ 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."

Design Submittal

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

5 Comments

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser BuildingGreen, Inc.
Jan 30 2013
LEEDuser Moderator

spaces with a lot of activity

I got this comment from a LEED user. Any thoughts? How is USGBC expecting spaces outside the scope of ASHRAE 55 to be handled?

"Recent 2009 Schools reviews on IEQc7.1 have requested information on how high activity spaces that fall outside the guidance of ASHRAE 55 were designed to maintain some level of thermal comfort for the occupants."

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Anthony Hardman Building Performance Analyst, The Green Engineer Feb 05 2013 LEEDuser Member 49 Thumbs Up

Any reasonable narrative should suffice for spaces that are legitimately exempt due to high MET rates. I'm surprised GBCI even requested this information since there's no precedent I'm aware of to measure it against.

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James Keohane LEED Project Administrator TLC Engineering for Architecture
Nov 22 2010
LEEDuser Member
425 Thumbs Up

EQ7.1 Template Contractors Initials for O&M Manual

I have a project adminnstration question or two:

On page 1 of 3 of the credit template the initials of the Contractor are requred acknowleging that System Manual or O&M Manual has been provided to owner. Two questions:
1. Doesn't the acknowledgement of the Owner has recieved an O&M Manual make this a Construction Credit and not a Design Credit?
2. Practically speaking, how do you make the template available for the contractor to initial? Do you assign/share EQ7.1 responsibility with the Contractor?

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Carrie Webster Moseley Architects Nov 23 2010 LEEDuser Member 304 Thumbs Up

We just ran into this same issue! In the comments on this site for LEED NC 2009 - EQc7.1 there is some discussion about this, and one comments imlplies that the O&M manual signatory was removed, but that does not appear to be the case for your project or ours. We are sending a feedback inquiry through LEED online to try to find out what to do. Not only is it inappropriate to assign the contractor to inital a design phase credit, but nowhere in the reference guide that I can find does it say that this credit will require documenting a systems/O&M manual. I hate being blindsided by something on the template that is not mentioned in the credit requirements!

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Dec 08 2010 LEEDuser Moderator

Have you guys checked that your LEED Online forms are as up to date as possible? No BETA marking on the bottom? They don't get updated automatically....

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