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.
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.
Areas with a metabolic rate outside of 1.0-1.3 need to use a different tool to show compliance with ASHRAE-55 for that space. As noted in relevant LEED interpretation #10279 (see above), most spaces with MET levels above 2.0 need to meet the cooling and humidity temperature set points for spaces with MET levels of 2.0 in order to meet the intent of EQc7.1. In order to demonstrate compliance, project teams need to complete one of the following two options:
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 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, and you will have to install a permanent monitoring system to provide ongoing feedback about thermal conditions. If you are only pursuing IEQc7.1, there is no requirement for a permanent monitoring system. Residential projects cannot earn IEQc7.2.
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 New Construction and Major Renovations
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:
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 55-2004 (with errata but without addenda) 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.
This updated version of the 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. Up to date, 2nd Edition.
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 is the 1st edition.
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.
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.
The following links take you to the public, informational versions of the dynamic LEED Online forms for each NC-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.
The new v. 4 forms table IEQc7.1-1. Space Design Parameters asks for the "Activity Level" to be listed per each space type. Are they asking for the MET rate? Or do they actually want the activity name - for example "sleeping".
Looks to me like it could be either. I'd use MET rate if you can provide it.
We got the comment as follow:
"However, the supporting documentation to confirm that all design conditions fall within the ASHRAE 55-2004 acceptable ranges has not been provided as required. While the narrative and load calculations indicate the design temperature and 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., they do not appear to indicate whether the design HVAC system is capable of meeting these setpoints."
What is the "support document" as metioned by the reviewer? do they look for the load calculation output from the software?
can anyone help
Did you include thermal comfort charts for each type of space and each season similar to the one at:
You can get the ASHRAE thermal comfort tool software for $117 at:
or you can use a free online tool available at:
I highly recommend downloading Google's free Chrome web browser and using it if you are going to try using the Berkeley free online tool. You can get Google Chrome at: www.google.com/chrome/
That would cover the part about whether all design conditions fall within the ASHRAE 55-2004 acceptable ranges.
As far as whether the design HVAC system is capable of meeting these 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., I'm not sure exactly what the reviewer is looking for. Perhaps they would like to see process psychrometric charts similar to the one in the Documentation Toolkit tab of this LEEDuser, but I've never had to do that for this credit. Maybe a narrative describing the capacity and behavior of the actual HVAC system at various full load and part load conditions would suffice. Include a description of how the HVAC system meets both the temperature and humidity setpoints at full load cooling, full load heating, part load cooling, and part load heating, in order to include comfort conditions for all seasons in your narrative.
So if we use the software and get the suitable range of occupancy type. Then, we use this condition to size the system. And show that how system would react via psychrometric chart of both part load and full load condition. Will this approach is correct?
Also, in Thailand, there is no need for heating. So can we use the coldest day as a condition for part load of the coolest system? or should we use the other day?
You should also provide a written narrative describing how the system reacts in full load, medium part load, and also on the coldest design day. I would use the coldest design day for "winter" and somewhere between that and full load for "fall" and "spring".
Also be sure to include information for each space type at each of the full load and part load conditions analyzed, showing the range of acceptable temperature versus humidity comfort conditions for the clo level of the occupants, met level of the occupants, and air speed, with your 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. or expected conditions for the various load conditions shown as falling within those comfort ranges.
If it gets a little chilly at times even though heating is not needed, you could use a higher clo level for that time of year if people would often wear a bit more clothing at that time.
Thanks so much
Normally, we will submit
1 Out put from the sofware (comfort report) of all activities (seated office, walking corridor, etc,)
2 HVAC analysis of each space with 5 condions (summer fall spring winter). This should have tick reports. let's say 50 zones with different HVAC sizes.
Is this fullfilled the requirement?
That sounds reasonable except that 50 zones is probably too many to describe individually. You should just analyze each different kind or type of space, not every zone. For example, office areas, meeting rooms, lobbies, etc. whichever types of spaces you have in your building. If you have 10 different office zones, just deal with that type of space once, not 10 different times.
The important things to focus on are:
1. Show that the conditions in each type of space with its own type of activity fall within the ASHRAE 55 comfort range for each season. You can do this with the comfort tool report, as you say in number 1 above.
2. Convince the reviewer in words that your combination of weather conditions, building characteristics, and HVAC systems will keep not only temperature but also humidity in the comfort range at part load conditions ("spring, fall, winter") as well as at full load conditions. A description in words may be more effective at doing this than numerical reports on 50 different zones would be.
Thanks. By the way, anywhere I can find such written narrative example?
Here's what I wrote in response to a review comment on an NC version 2.2 project. The credit was awarded. The details of the question were different than in your case, but similar in that the reviewer needed to know that comfort conditions would be maintained for all design and part load conditions.
"The reviewer has requested further information on the operation of the 2-pipe system and how it is designed to react to rapidly changing climate conditions in intermediate seasons. The reviewer has further requested clairification on the operation of the heating only loop specifically how the 148 degree water running thru the cabinet heaters and the radiant floor will not cause the building to over heat.
The following narrative is provided to help clarify these issues:
1. Two Pipe system:
Active conditioning is used in all spaces. Winter and summer design criteria fall within the standard 55 envelope. Spring and Summer criteria fall within the combined winter and summer envelopes.
The dual temperature hot/chilled water system is isolated from the area chilled water and hot water loops by heat exchangers. One heat exchanger is dedicated to heating and the other to cooling. The dual temperature system serves only the [6,000 square foot new wing], limiting the volume of water in the loop. When the dual temperature loop is in heating mode, the chilled water heat exchanger is isolated and vice versa. In heating mode, the hot water supply temperature in the dual temp loop is reset from 150 to 100 deg F as the outdoor temperature varies from 10 to 60 F. Automatic change over between the heating exchanger and the cooling exchanger is provided by the DDC controls based on outdoor air temperature.The DDC control system will automatically change the system from heating to cooling, and the air systems all have economizerAn economizer is a device used to make building systems more energy efficient. Examples include HVAC enthalpy controls, which are based on humidity and temperature. controls.
2. Heating Only Loop
The area heating loop serves the vestibule heaters and the radiant floor. The radiant floor system has its own circulating pump and a 3-way valve to allow mixing radiant floor return water into the radiant floor supply water, for independent temperature control of the radiant heating loop water. In addition, the zones served by the radiant loop are automatically shut off by control valves when the thermostat in the zone is not calling for heat. The vestibule heaters cycle two-position control valves and fans based on the DDC sensor in the space.The water temperature to the heating loop is also reset based on outdoor air temperature and is only at 148 degrees when the oudoor air temp is at 0 degrees."
Thanks, here is what I wrote.
VRF Cooling Operation Mode
AC units will supply the constant air flow to the space. Supply temperature will be moderated to accommodate different load scenarios by using zone thermostat. Variable speed compressor varies the refrigerant pressure to smoothly control the supply temperature which allows effective dehumidification at the cooling coil. In turn, space temperature and RH can be effective controlled. In peak load scenario of summer, the properly sized HVAC handles full cooling load by maintain low supply temp (55F) which can control the designed zone temp and RH. In part load scenario of fall, cooling load reduces due to lower outdoor air but humidity increases. To maintain the temperature, constant supply air need to be warmer. This can increase RH because the dehumidification at the cooling coil reduces. To meet the ASHRAE 55 criteria, the cooling coil was carefully designed to balance the capacity of sensible and latent heat removal. In near zero load scenario of winter, the outdoor air can be close to the indoor design temp. Supply temperature can be very close to the indoor temperature. Fortunately, the humidity of the season is low and do not require dehumidification.
VRF Heating Operation Mode
In the coldest day of Thailand, the temperature is slightly lower than the indoor set point. However, solar radiation, lighting, appliance, kitchen equipment, and occupants are the internal cooling load of KFC during the operation period. These heat can be 15-40 W/sqm and always rise the zone temperature (if no HVAC) to be higher than the outdoor. Simply put, the HVAC will never operate in heating mode. In this coldest day, the VRF system will operate similar to part load or near zero load scenarios as described in the previous section.
The narrative looks very good. I have two suggestions that would strengthen it, if they apply to your VRF system.
I believe some VRF units automatically vary fan speed as well as supply air temperature. If this is true of your units, stating that fact will strengthen the case that they will dehumidify well due to the latent/moisture portion of the heat removed by a cooling coil increasing as airflow decreases. In addition, some VRF thermostats have an option to choose "dry" mode. That could be another help in assuring good dehumidification is available, if your VRF thermostats have a dehumidification mode option that can be selected by the occupants.
Here's part of what I wrote on a VRF heat pumpA type of heating and/or cooling equipment that draws heat into a building from outside and, during the cooling season, ejects heat from the building to the outside. Heat pumps are vapor-compression refrigeration systems whose indoor/outdoor coils are used reversibly as condensers or evaporators, depending on the need for heating or cooling. In the 2003 CBECS, specific information was collected on whether the heat pump system was a packaged unit, residential-type split system, or individual room heat pump, and whether the heat pump was air source, ground source, or water source. project in response to a similar review comment on a version 2.2 project. The credit was awarded.
"Humidity Levels During Periods of Low Cooling Load --
Latent cooling (dehumidification) during periods of varying cooling loads is addressed by: 1) a "dry" setting on the individual indoor heat pump fan unit occupant-adjustable thermostats, which reduces sensible capacity and increases latent capacity, 2) latent heat exchange between exhaust air and incoming outdoor ventilation air in the energy recovery ventilation system, and 3) tempering cooling/heating coils in the mechanical ventilation supply ductwork. These features, when combined with internal sensible heat gain, provide the ability to reduce total moisture levels and relative humidity even under conditions of low sensible cooling load."
In first place, I apologize for my English. I hope that my text will be quite understandable.
Our project is a mixed use hospital and laboratories of 1 400 000 ft² and 2 400 spaces in Canada. We are using the Ashrae Standard 55-2010 Comfort tool to calculate the PMV/PPD for proving that the design is good relative to Ashrae 55-2004.
For short, we have reduced the 2 400 spaces of the project into 60 spaces types.
According to Ashrae 55-2004, we have excluded the spaces where occupants are staying under 15 minutes and where they can sleep or bed rest, such as patient room or recovery room. So we have grouped the remaining areas under the same environmental characteristics:
- Air temperature set (for the 4 seasons)
- Humidity set
- Metabolic Rate
- Clothing level
- Mean Radiative Temperature ( We have seen that the MRT is the factor who have the lowest incidence on the PMV/PPD, so we have decided that we split this characteristic in 3 categories (internal area, space with one exterior side, space with two exterior sides))
That is why we are able to reduce the number of cases at 60, instead of 2 400.
Is our interpretation of the Ashrae 55 correct so far?
We are wondering how to define/justify the air speed in each space. The air speed must remain below 40 fpm in the Ashrae Standard 55-2010 Comfort tool to be consistent with the Ashrae 55.
How can we calculate the air speed at human height?
Have we to make a CFD simulation for each space? Or is there a formula with the air speed at the output from the diffuser capable of calculate the airspeed at human height?
Maybe can we use the same air speed for the 60 spaces on taking the most conservative air speed value for all the spaces?
Your help is more than appreciate on this,
No, you shouldn't have to do a CFD simulation. In general, conventional diffuser selection and layout will result in being below 40 fpm air speed in the occupied area.
To get a better understanding of the air speed, you could look at the application guide from a diffuser manufacturer, such as Titus or Price.
Your approach sounds right to me.
-Julia G. Weatherby, P.E.
Thanks Julia to give me book references.
So, according to section 9.4 of "Engineer's HVAC handbook" from Price, if we can prouve that the throw of our 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. is (much) larger than the throw of the manufacturer at 50 fpm, the project probably met the standard 55?
It would be more understandable if LEED council want us to prove that the air is blowing under 50 fpm (instead of 40 fpm) in the occupied zone..
I think you probably understand fine, but it is not specifically that you want your 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 have a large throw. It's that you want the air to slow down to 40 fpm or less by the time it reaches the people sitting or standing in the occupied space.
As long as your diffusers seem to be generally properly selected, it should be fine to assume a fixed velocity, such as 20 fpm average air velocity, in all your spaces. If you have any spaces with unusual characteristics, then it may make sense to do a specific air velocity estimate for that space.
Just to be more specific, our mechanical design team is selecting the 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. in accordance with the manufactuer throw data at 50ppm. Fo now, I’ve made my calculation in the Ashrae Comfort Tool with an air velocity of 30ppm.
So, can we just saying, in our explanation letter who goes with the Letter type, that
“Our mechanical design team has selected the diffusers according to the generally accepted engineering practices and the manufacturer data throw at 50ppm, so we can consider that the air velocity to the occupant height is lower than 30 ppm (or 40ppm)”, to be consistent with the credit 7.1 requirements?
Thank’s a lot for your help
That seems fine to me, Cedric. I'm not sure you really need to include any justification for the air velocity used unless specifically asked to do so by a reviewer, but it is fine to include the statement if you are more comfortable doing so.
Ok, we will do that.
I m a beginner in the Leed project certification and honestly I'm not aware of the reviewers want for accuracy.. So i prefer to explain all my interpretation :)
Thank's a lot
So I recently got hired, and the first thing they have me working on is getting familiar with LEED credits and completing the forms. This may sound like a dumb question, but how do I determine the Operative Temperature for Cooling and Heating? I already obtained my climate design conditions from our Load Calc program.
Welcome to LEEDuser! Does your office have a copy of ASHRAE Standard 55? The operative temperature is clearly defined, as well as other terms and requirements for this credit. The comments on this page are also helpful, so have a read and don't be afraid to ask more questions.
The operative temperature is based on the local air temperature and the mean radiant temperature (which is a function of radiant heating/cooling sources). If your spaces have a reasonably good building envelope and no radiant heating/cooling systems, you can assume that the operative temperature equals the local air temperature. See Appendix C in ASHRAE Standard 55-2010 for details.
Yeah I've read through ASHRAE 55 and Apendix C and that's what I thought. I'm just always hesitant on assuming. I appreciate the help.
Many thanks to Christopher Schaffner for linking in his post below to the Berkeley CBE free online comfort tool at: http://cbe.berkeley.edu/comforttool/
I use the Windows XP operating system, and I wanted to pass along the info that the CBE Comfort Tool online works best in the Chrome browser. Google's Chrome web browser can be downloaded free at:
I couldn't get the CBE Comfort Tool to work at all in Firefox or Internet Explorer 8 on my Windows XP machine at the office. It worked pretty well in Firefox on a different computer (not sure of operating system), but still had a couple oddities on the temperature input options. Those oddities were completely resolved on my Windows XP machine at my office when I downloaded the Chrome web browser and used it to run the Comfort Tool.
I am in the process of preparing the documentation for this credit but have a few a few questions regarding ASHRAE 6.1.1 Documentation and associated calculations. Apologies in advance for the lengthy query.
1. Does the psychrometric chart need to be submitted despite providing PMV/PPD result from ASHRAE thermal comfort tool?
2. If so, where can we obtain a psychrometric chart suitable for LEED Upload?
3. Do we have to calculate the thermal comfort for each and every zone in the project? Or can we provide the calculations for the representative zones by space usage type? For example, on our project, we have several types of offices, retail spaces and hotel spaces as well. However there are over 500 individual zones on the project. So can we apply the calculation for each "type of zone" rather than for each individual zone?
4. How to demonstrate design compliance in accordance with ASHRAE Section 6.1.1 documentation?
Should we write a narrative in accordance with ASHRAE Section 6.1.1 documentation? especially, Otherwise I am not sure how to demonstrate and meet the building envelope part according to ASHRAE 55-2004.
5. Finally, is the indoor air speed equal to air speed from diffuser of 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. system?
1) The psych chart is not mandatory, but you should provide information about all seasons and part load conditions. This could be a narrative.
2) there are many psych chart tools available - google 'psych chart'.
3) not each zone, but each space type.
4) provide a narrative
5) indoor air speed depends on diffuser selection. The air speed we care about is the air speed an occupant will feel, not the diffuser discharge velocity. Look at the throw characteristics of the diffuser. Most diffuser data sheets show the throw at different velocities - i.e. the distance from the diffuser at which that velocity exists. For most situations you want the velocity at the occupant to be 40 FPM or less.
Thank you very much for your help. It is greatly helpful for me in performing this project and completing this credit.
My project was given the following comment. We haven't seen this comment before and we don't know how we would provide PMV/PPD calculations. Can anyone on here help to clarify?
Thanks in advance!
However, although the narrative provides sufficient information to confirm that the thermal comfort conditions meet ASHRAE 55 requirements for the typical office space, dining space, and meeting rooms (since Figure 18.104.22.168 of the Graphical Method can be applied), sufficient information has not been provided for the kitchen/cooking areas. Figure 22.214.171.124 would not apply to these spaces since the metabolic rates listed are between 1.6 and 2.0 which exceeds the upper limit of 1.3 met for using the Graphical Method.
Please provide further information, such as PMV/PPD calculations to demonstrate that the thermal comfort conditions for the kitchen/cooking areas meet ASHRAE 55 requirements.
If your kitchen/cooking areas have activity levels up to 2.0 met and clothing levels up to 1.5 clo, then you can use the computer model method. This method has a wider range than the graphical method, as noted in the review comment. There are a few software options available, I use the "ASHRAE Thermal Comfort Tool" (purchase from ASHRAE) and "Climate Consultant" (download from UCLA).
If your activity levels exceed 2.0 met, see discussion comments below regarding high-activity spaces. The ASHRAE 55 PMV-PPD model is only useful for spaces with activity within 1.0-2.0 met and no more than 1.5 clo, so you'll have to show alternate strategies to address thermal comfort in such spaces.
The CBE Thermal comfort tool also will calculate PPD/PMV. Although it gives the warning "Does not comply with ASHRAE Standard 55-2010
↳ Metabolic rates below 1.0 or above 2.0 are not covered by this Standard"
it still performs the calculation.
Available free at http://cbe.berkeley.edu/comforttool/
I used the CBE Thermal Comfort Tool for documentation on a project after seeing it referenced here. It seems to work best in Google's Chrome web browser. Thanks!
Our project is a car showroom in a location where no air conditioning nor heating is needed due to the mild clima throughout the year. This is an occupied, enclosed space. There are no windows and no mechanical equipment to condition this space. Ventilation is given with a injection fan.
How is this space CONDITIONED according to ASHRAE 90.1: naturally, mechanically or neither of them?
The revised documentation shows that the Showroom space is occupied, enclosed space, but is neither mechanically or naturally conditioned. The response narrative implies that this area is exempt from the requirements of the credit. This is incorrect. The documentation does not demonstrate credit compliance.
If there is no installed heating or cooling capacity, then it sounds like the space is either "indirectly conditioned space" or "unconditioned space" as per the definitions in ASHRAE 90.1. Is the injection fan capacity for ventilation only, or is the outdoor air also used for cooling?
Section 5.3 of ASHRAE 55 discusses a method to determine thermal comfort conditions in naturally conditioned spaces. However, this method relies on occupants having control over operable windows to adjust conditions in the space, which doesn't sound like it applies to your project.
It sounds like you still need to show that the space has acceptable thermal comfort conditions as per ASHRAE 55. The results would indicate if no mechanical heating or cooling is required to maintain acceptable conditions.
Our project is a major renovation to an existing college faculty office building with very low floor-to-floor heights. The lack of plenum space made air distribution ducts infeasible... however, all rooms have access to operable windows (the building was built in 1914, and was therefore designed for natural ventilation). Heating and cooling is provided by a 4-pipe fan coil in each room. Our application for IEQc7.1 is pending, because the LEED reviewer wants us to demonstrate that the fan coil units that serve the individual offices are designed to handle the ventilation loads with operable windows fully opened. Why would this be necessary? Isn't it safe to assume that an occupant will adjust/close the windows when thermal comfort falls outside the parameters? It seems to me that we should only have to demonstrate that the loads are met with the windows open to meet minimum ventilation requirements. Has anyone else run into a similar situation?
Eric, it sounds like your design is using the windows for natural ventilation and the fan coils for mechanical conditioning. Section 5.3 in ASHRAE Standard 55 outlines a method for using operable windows to naturally condition spaces, but sounds like it won't apply to your design. In that case, I think your fan coils must do the work to maintain thermal comfort conditions, including the heating/cooling/dehumidification loads from unconditioned ventilation air. The windows are for ventilation only, not conditioning.
How much difference is there between the window "minimum opening for ventilation" and fully open? Is it clear to the occupants when or how much they should open the windows?
Eric, i am also in same boat. i am using operable windows for ventilation in apartments. do you know how to demonstrate it?
Anil, we ended up abandoning the credit, since we were able to achieve Gold certification without it. I would have liked to push for a resolution, but time and fee just wouldn't allow it. Lindsay, here's how the occupants know when to open the window: it's when they feel stuffy and/or when the weather is nice, just like they did it in 1914 when the building was built. We complied with ASHRAE 62.1 using the natural ventilation floor/window ratio method. The rooms are all different: floor area, number & type of operable windows, so there's no consistency. In some rooms, there is a significant difference between minimum opening for ventilation and fully open. So, if the windows are fully open on the hottest day of the year, can the fan coil handle that load? Of course the answer is "no". The design team rightfully assumed that if the room is hot on the hottest day of the year with the window open, the occupant would close down the window and let the A/C do it's thing. The building is full of smart people -- college professors -- and we like to think they know what to do with an operable window. ;) Unfortunately, we can't "engineer" user discretion, so it won't pass muster with the LEED reviewer.
our project is mixed use commercial building, including office, hotel, retail store, and restaurant etc. All spaces in our project comply with ASHRAE 55 except for commercial kitchen. There is no AC unit there and conditioned air is delivered from adjacent restaurant dining room and exhausted through fan located in the commercial kichen. So the kitchen air is conditioned indirectly. Our question is that the commercial kitchen may excluded from ASHRAE55 evaluation or not. Thank you for your kind advice in advance.
Noriko, I don't see how you can exclude it. See other discussions on this page about excluding high-activity spaces like gyms. LEED really makes you work to exclude 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..
A new 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. was released on 4/1/13 that is relevant to this credit.
LI #10279 disallows excluding high-activity spaces like gyms, or spaces that normally are not conditioned like warehouses from IEQc7, but offers an alternative calculation method for gyms, and an alternate compliance method for warehouses based on design alternatives such as radiant flooring; circulating fans; passive systems, such as nighttime air, heat venting, or wind flow; and localized active cooling.
I asked our LEEDuser expert Chris Schaffner of The Green Engineer what he thought about this Intepretation. He says it clarifies things, but doesn't help where help is needed: '95% of the people struggling with this are public schools with gyms. They should just make the gyms exempt,'" he opined.
What do others think of this Interpretation?
The LI states that, "an alternative to the requirements of ASHRAE 55-2004 is acceptable" in these circumstances. I recently saw a project team propose the use of a health/fitness facility standard that would appear to meet the intent of this interpretation.
I've been involved in two recent projects which included in one case, indoor tennis courts, and in another case, a fitness center. The interpretation does nothing to remove the vaugeness that existed before. By saying "the project must determine acceptable thermal comfort conditions that meet the intent of the credit, and demonstrate that those conditions will be met" they leave it up to us to propose something and we are at the will of the reviewers opinion. So to me, the interpretation still leaves the credit in "limbo" for those spaces and I can't count on it in our credit/point strategy. We will do a lot of work researching and proposing a set of criteria, not knowing if it will be in vain depending on how the reviewers see it. That's the status of our application now for the project with the fitness center. We're waiting to see how the reviewers treat us.
This area does need work. We have had a couple of projects certified with these kinds of spaces (one had a gym, the other had a fitness room), and we included a narrative on what we felt was the standard of care for these kinds of rooms, higher temperature with air movement, and that seemed successful. Another is yet to be submitted that the whole building is a fitness, training, pool, and therapy building that is a shared facility for a hospital and a community. The pool has pretty good standards for defining comfort, but again the other spaces will fall on our standard of care and typical practice over our experience.
Nadja, your point of not being able to count on this credit is correct. We work to manage our clients expectations on this and other credits so they understand we are making a good faith effort, and giving them what we feel is the best and most efficient design, but we are not GBCI and cannot predict what they will or will not accept. There is a broad range of professional interpretation in our field, and we all must work within it.
Project consist of Heating only system for dinning area (for inmate), and for summer ventilation the unit provides the 6 ACHThe number of times per hour a volume of air, equivalent to the volume of space, enters that space. ventilation air into the area. Project location is in MD.
Since this building is for inmate the owner does not want to provided cooling for dining area.
Can i able to get this credit, what kind of document i need to provide to support.
Thermal comfort standards apply to all humans, regardless of criminal record. If you aren't providing comfort you can't get the credit.
LEED shouldn't be certifying prisons.
I just re-read Nadja Turek's earlier comment (from Aug 29, 2012) which included this excerpt from a 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 response:
"The metabolic rate for occupants involved in highly physically activity fall outside the range governed in the standard, therefore, thermal comfort conditions must be based on acceptable practices. The project should utilize an alternative compliance method or extrapolation of existing data to show compliance with the
credit for the spaces which fall outside the range of standard 55-2004.
ASHRAE 55-2010 has a revised computer simulation method which accommodates MET levels up to 5.0."
The problem is, ASHRAE 55-2010 specifically states that only rates between 1.0 and 2.0 MET fit within the PMV-PPD model, and only 1.0-1.3 MET for the adaptive model (see section 126.96.36.199, 5.3 and Appendix A).
The ASHRAE Thermal Comfort Tool v2 software (which follows ASHRAE 55-2010) allows an input value up to 5.0 MET... but it also generates a notice that this rate is not covered by the standard, if you try to enter anything above 2.0 MET. It seems to me whoever responded to Nadja's CIR misunderstood that.
Does anyone have a project that achieved this credit with spaces that fell outside of ASHRAE 55 parameters? Has any direction been given for alternate compliance? James Del Monaco posted his discussion with a reviewer back in Nov 2010, but it seems many are still looking for clarification on this.
I have the same understanding. GBCI shouldn't be asking project teams to comply with ASHRAE 55 when the conditions clearly fall outside the boundaries of the standard. 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 aren't precedent setting anyway, so I would ignore this and simply state the exception to the standard from Appendix A.
We have been successful excluding zones in some projects that are not covered by ASHRAE 55, and that were outside the bounds of the standard with MET > 2.0. At that point we do include some narrative on what we did to address that condition, and what the standard of practice was for those zones. For example, ceiling fans in a fitness room to increase air movement over machines.
I heard from someone in ASHRAE that the Standard 55 User's Manual is definitely in development and will be "coming soon". Hopefully it will be available later this year?
We are targeting this credit for a project with more than 70% of the buildings are utilised for industrial, processing, storage and manufacturing activities. Does the credit apply to these type of spaces?
I'm currently confronted with the same issue, and I have similar questions:
In the spaces used for processing, the metabolic rate of the occupants as well as their clothing may fall out of the limits of both comfort calculation methods proposed in ASHRAE 55-2004.
Does that mean that this credit cannot be applied for these type of spaces?
Or is there any other comfort calculation method more appropriate (not based on sedentary office activity)?
Or should I just exclude these spaces from the credit scope?
Thanks all for your clarifications.
Ismaiel, it's not the space type but the activity that occurs within those spaces that determines whether this credit is applicable. If the clothing and metabolic rates of the occupants in each space fall within the ASHRAE Standard 55 models, then it applies.
Valentin, based on what I've seen you probably will not be successful with this credit if you have activities/spaces falling outside of the ASHRAE 55 models. I believe projects are unable to exclude any 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. from the credit scope even if they do not fall within the limits of either the PMV-PPD or adaptive models in ASHRAE 55. See some of the older posts on this thread, as well as the LEED Interpretations database.
(I work mostly on LEED Canada projects, and the CaGBC does allow spaces to be excluded if they can be justified based on the limits of ASHRAE 55.)
Does ASHRAE 55 standard apply to areas with transient occupancy such as smoking lounges in airports, Knowing that smokers will spend less than 15min in average?
No, ASHRAE 55 is intended only to model thermal comfort in a 'steady state' and is applicable when occupants are in the space for no less than 15 minutes.
I've submitted this credit to USGBC and it was rejected. The reviewer stated that the design air speed values exceed 40 fpm and therefore do not meet ASHRAE 55-2004 (I have a range from 50 - 70 fpm). However, i've used two tools that show the scenarios do comply. Climate Consultant 5.0 and the Berkely tool referenced on this site. Air temp of 75F, Mean radiant temp of 85F (large single pane historic windows), air speed of 70 fpm, Humidity of 50%, MET of 1.1, and 0.57 clo. What am i missing? The Climate Consultant graph is hard to follow (this is the one I submitted), perhaps if I submit the Berkely tool it will be more clear to the reviewer? I had a narrative explaining all the values I used as well. Any help is appreciated.
I have researched this more, and have found that air speed values above 40 fpm are allowed but only if Section 5.2.3 are met, which requires occupants to control the air speed. We have 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. boxes, so the occupant can slow the air speed by raising the room setpoint. But every occupant does not have their own thermostat, therefore it sounds like we do not meet this credit. anyone have any other thoughts?
Barbara, this credit is not a particular expertise of mine, but at a glance, I wouldn't have thought that controls for individual occupants factor in here. Isn't that under IEQc6?
I thought so too, but ASHRAE 55 mentions allowing "elevated air speeds" above 40 fpm at the occupant level if the occupant has control over the air speed. I am very ready for ASHRAE to publish the User's Guide for ASHRAE 55. I'm wondering if anyone has ever achieved this credit with air speeds above 40 fpm?
Barbara, I've been getting this feedback from LEED as well but I think the LEED reviewers (as well as others below on this forum) are incorrect. Section 5.2.3. is specifically to show the designer that you can maintain thermal comfort with higher ambient temperatures than shown in figure 188.8.131.52. if air speeds are increased above 40 fpm. Their chart shows how high the temperature limit can increase for corresponding air speed increases (and given air and radiant temperatures). I've had to explain this to LEED consultants as well with varying degrees of success.
I believe ASHRAE 55 includes this to provide a guideline to those who would like to design for less mechanical cooling while keeping comfort at the same time. I do not read this to be an absolute that 40 fpm is the comfort limit and any speed over that is uncomfortable.
Discomfort due to draft is covered later in 184.108.40.206. You can see there may be certain circumstances where 40 fpm would be the limit, but not always.
We'll see if LEED agrees when I get a review of my response.
Jeremy is correct that Section 5.2.3 includes provisions for increasing airspeed to offset elevated space temperatures for individual comfort. However, this option is only applicable if the affected occupants can control the airspeed.
What MET rate would you assume for the ASHRAE-55 compliance for retail areas (ie. supermarket, clothes retail)? Customers would be walking about (MET:1.7), while employees would be either standing or seated (MET: 1-1.2). In summary, for whose comfort should retail spaces be designed for, customers or employees?
It is noted in ASHRAE 55 Normative Appendix A (Activity Levels) that each group of occupants must be considered separately, and that it may not be possible to provide an acceptable level of comfort to all occupant groups.
In your case, you would analyze thermal comfort for employees and customers as separate cases, then ensure that you can satisfy both cases.
I am working on a mechanically ventilated manufacturing building in Bangladesh. What is the maximum acceptable temperature for this kind of building? In summer they usually get 36C and a relive humidity close to 70%.
Thank you responding.
You need to perform a comfort analysis to determine the acceptable indoor conditions. It will be based on factors such as activity level and clothing.
36c at 70RH% is certainly far outside the comfort zone.
The IEQc7.2 Cooling Mode table asks for the Design Operative Temperature, Maximum Design Humidity and Design Air Speed for the four seasons (Spring, Summer, Fall, Winter). Is it OK to complete only the Summer values?
Thanks in advance.
No - you need to account for all four seasons. This is one of the main objectives of the credit - to make sure that part-load conditions are being considered and addressed. Humidity control is sometimes difficult to achieve under part-load conditions.
Which software tools are accepted by the USGBC, other than the ASHRAE Comfort Tool (priced at $117)?
Is the tool from Climate Consultant listed under the Resources Tab accepted? What about the Thermal Comfort online tool developed by CBE Berkeley (http://www.cbe.berkeley.edu/comforttool)?
USGBC does not officially "accept" any software tools. If the tools listed are used correctly, they can perform the analysis required by the credit.
Just received an email about a new tool that may be helpful for teams pursuing this credit:
The Center for the Built Environment has developed a web-based thermal comfort tool, which is now available for use: http://cbe.berkeley.edu/comforttool/. This free online tool is useful for performing and visualizing comfort calculations according to ASHRAE Standard 55-2010. The tool has been validated against the official ASHRAE Thermal Comfort tool. The tool could be used for design, research and teaching. The tool works in Firefox, Chrome and Safari. Internet Explorer is not supported.
The link is not opening in chrome & firefox. Any other link to access this tool ?
Is it applicable for only naturally conditioned spaces?
This brief guide introduces some of the key variables involved in designing for thermal comfort.
Principal & Founder
The Green Engineer, LLP
Teams must achieve IEQc7.1 in order to earn IEQc7.2. IEQc7.2 offers an opportunity to confirm that the system design and ASHRAE-55 requirements are working to deliver occupant comfort.
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.
LEEDuser members get it free >
LEEDuser is produced by BuildingGreen, Inc., with YR&G authoring most of the original content. LEEDuser enjoys ongoing collaboration with USGBC. Read more about our team
Copyright 2014 – BuildingGreen, Inc.