This credit 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.
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.
Base building mechanical systems have to allow for the tenant fit-out to meet the requirements of ASHRAE-55. If all the mechanical systems are relegated to tenant fit-out, LEED-CS projects are not eligible. Consider this early in the planning phase of a core-and-shell project.
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 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.
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.
Supply air volume (CFM) is different from linear air speed measured in feet per minute (FPM). Linear air speed in FPM is relevant to comfort requirements. This information can be derived from the diffuser throw value.
You can establish compliance based on an alternative method to ASHRAE 55.
For spaces with a time-averaged metabolic rate above 2.0 MET, the project must determine acceptable thermal comfort conditions that meet the intent of the credit, and demonstrate that those conditions will be met. See 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. #10279 for more details.
For spaces such as warehouses that are not normally conditioned for comfort, the project team may include one or more of the following design alternatives: radiant flooring; circulating fans; passive systems, such as nighttime air, heat venting, or wind flow; localized active cooling (refrigerant or evaporative-based systems) or heating systems; or localized, hard-wired fans that provide air movement for occupants' comfort. Again, see LI #10279 for more details.
Base building mechanical systems have to allow for the tenant fit-out to meet the requirements of ASHRAE-55. If all the mechanical systems are relegated to tenant fit-out, core-and-shell projects are not eligible. Consider this early in the planning phase of a LEED-CS project.
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.
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 IEQc6.2: 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 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:
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.
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.
Develop the Systems Manual, O&M manual, or equivalent. Ensure that the O&M manual includes the following:
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.
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.
Excerpted from LEED 2009 for Core and Shell Development
To provide a comfortable thermal environment that promotes occupant productivity and well-being.
Design heating, ventilating and air conditioning (HVAC) systems and the building envelope to meet the requirements of one of the options below:
The core and shell base building mechanical system must allow for the tenant build-out to meet the requirements of this credit. See Appendix 1 — Default Occupancy Counts for occupancy count requirements and guidance. Project teams that design their project for mechanical ventilation that do not purchase or install the mechanical system are not eligible achieve this credit.
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.
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 552004); 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.
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.
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) according to ASHRAE Standard 55-2004 (with errata but without addenda1) that support the desired quality and occupant satisfaction with building performance. Design the 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 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. Performance, IEQ Credit 1: Outdoor Air Delivery Monitoring, and IEQ Credit 2: Increased Ventilation.
1. Project teams wishing to use ASHRAE approved addenda for the purposes of this credit may do so at their discretion. Addenda must be applied consistently across all LEED credits.
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.
The following links take you to the public, informational versions of the dynamic LEED Online forms for each CS-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."
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.
I am bit confused about the requirements of the Thermal comfort-desing’ credit for C&S
Can you please help me on figure out if my building is eligible or not.
The building is mechanical ventilated, I provide fans that will supply outdoor non-conditioned air for all the occupied spacesOccupied Spaces are defined as enclosed spaces that can accommodate human activities. Occupied spaces are further classified as regularly occupied or non-regularly occupied spaces based on the duration of the occupancy, individual or multi-occupant based on the quantity of occupants, and densely or non-densely occupied spaces based upon the concentration of occupants in the space.. Furthermore, there will be chillers and water cooling-piping in each 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., the way each tenant install their own equipment (fan-coil)
This credit is pretty clear. Look at the requirements and you will find: “Project teams that design their project for mechanical ventilation that do not purchase or install the mechanical system are not eligible achieve this credit.”
Based on your description, you would not be able to pursue this credit, but the tenants could under CI if they design their distribution systems correctly.
How should I conduct PMV and PPD calculations for a shopping mall? Should I do the calcutaions only for shopping mall employees or do I also have to conduct seperate calculations for transients?
Typically, malls do not install their tenant systems as part of construction, so I do not think you can pursue this credit. Sorry.
Do we have to provide documentation that the design conditions fall within the ASHRAE 55-2004 just for regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building. (e.g. office, conference, retail) or for all space types including restrooms, corridor, storage?
The ASHRAE 55 says: " This standard specifies thermal environmental conditions ... in indoor spaces designed for human occupancy for periods not less than 15 minutes."
For me this means that corridors, restroom and storage areas are not included, just the regularly occupied spaces as they are defined by the RG.
However, the LEED Review team told us to provide documentation for each space...
We have submitted for only those spaces required by the standard as you indicate and have not had a problem. Perhaps in the narrative repeat what the standard says, and why you feel you have complied, then show the calculations.
Can a project without humidity control get a point under this credit?
If local climate conditions don't require humidity control (desert location), then the point can be earned without humidity control.
In a humid climate, you don't need explicit humidity control if you can show that humidity is controlled as part of the air conditioning process.
We have a commercial project that is going to pursue Core & Shell. To meet energy goals of the owner, a central plant with high efficiency boilers and chillers will be installed, sized to support the common spaces AND the tenant spaces. The individual tenant fan coil units and ventilation units will not be installed, but the four-pipe system will be distributed to all tenants, and they will be required to use them (in the lease agreement).
The common spaces will include full comfort conditioning. There are only two buttons on the LEED Online template, purchased or not purchased. We are purchasing MOST of the equipment, but not all of it. We are purchasing ALL of the systems related to common spaces, where we can definitely do ASHRAE 55 comfort calculations.
We can find no CIRs or other guidance, but it does not seem fair that this work would go un-recognized. I think the intent is to not give this credit if you are allowing tenants RTUs or other systems that are not as efficient or flexible in application as the one we are suggesting.
Has anyone had any experience with this? Are we answering the question in the template on purchasing for our common spaces (under control of the developer), or for the total building?
The credit language says:
"Project teams that design their project for mechanical ventilation that do not purchase or install the mechanical system are not eligible to achieve this credit."
Since you are not providing the devices that would condition the air - the fan coils and make up air, you cannot achieve this credit.
I have the following confirmation from the USGBC:
"You do not need to install the mechanical system in the tenant spaces, but, per page 535: The core and shell base building mechanical system must allow for the tenant build-out to meet the requirements of this credit.
You must install the base building systems, and the base building systems must allow tenants to build out systems that can also comply with the requirements of this credit, but you do not have to install the tenant mechanical systems."
I think I agree with Scott that a shopping mall installing the HVAC system in all common areas (as per ASHRAE 55) can achieve this credit.
We are working on a C&S project. The Design team states,
"The tenant spaces are typically served by roof-mounted central station variable air volume (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.) air handling systems. Capped connections have been provided for future fit out connection. The future tenants will connect terminal VAV units to serve each space as required for proper control and operation of the system."
My reading of this is that the tenant will be installing some of the mechanical systems of the project. If you click this on the template, the templates states that the credit cannot be achieved.
Is this a correct understanding?
I have the same doubt. Had someone answered this question before?
I do not see any responses to this thread. Has anyone achieved IEq c7 under 2009 CS when the base bldg provided the only air units, but not tenant ducts, boxes air devices?
The situation is different here. Since you have provided the AHUs, which provide ventilation air and conditioning, you are eligible to meet the credit. The lack of a full distribution system is pretty typical.
Thanks Christopher. I have the exact same situation, where C&S is installing the AHUs, chillers, boilers, and all duct mains onto each floor. We are not providing the distribution ductwork or VAVs to the tenant spaces. The only areas we are delivering comfort cooling/heating are the core areas. That being said, I was only going to document the space design conditions for these core areas and back it up with a narrative. Does that sounds like a viable method?
My project is registered under LEED CS v2.0, so the requirements may be a little bit different than CS v.3, however I hope you can still be able to help me.
If I understand corectly, this credit requires showing the locations of heating and cooling equipmentThe equipment used for cooling room air in a building for human comfort. (in my case thermostats and cooling beams) on the floor plan. How should I do it, if I'm certifying only core and shell spaces and I have no idea how the future tenants would like to design their premises. Shall I submitt a sample fit-out?
Alicja, I am not familiar with CS v2, but in v2009, this kind of question is addressed in Appendix 4 in the LEED Reference Guide. Perhaps you could review how it is handled there and come up with an approach for v2.0.
Under CSv2.0 you are not required to show locations of heating and cooling equipmentThe equipment used for cooling room air in a building for human comfort. for this credit. A narrative and supporting calculations should suffice.
As this is a design credit, during the design phase, can the air velocities be estimated, or does this credit need to be completed after construction to measure the air velocity?
Sheldon, you are expected to use the designed air velocities to document this credit.
Providing thermal comfort controls will help occupants be comfortable on a space-by-space basis.
Commissioning will help confirm that equipment set points and operating ranges will create system performance that is consistent with the design intent.
Ongoing measurement and verification of mechanical systems will confirm that systems are operating as designed and at levels that maximize efficiency and occupant comfort.
Do you know which LEED credits have the most LEED Interpretations and addenda, and which have none? The Missing Manual does. Check here first to see where you need to update yourself, and share the link with your team.
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