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 evaluate the ability of building systems to stay within a comfortable range of air temperatures, radiant temperatures, humidity, and air speeds during design weather conditions.
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. Earning this credit also sets the stage for you to earn IEQc7.2: Thermal Comfort—Verification.
Meeting this credit in naturally conditioned 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.
Mixed-mode spaces have a better chance. That is, naturally ventilated buildings can still meet the requirements of ASHRAE-55 if heating and cooling systems can keep indoor conditions comfortable year-round.
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.
International projects can choose to demonstrate compliance with ISO 7730: 2005 and CEN Standard EN 15251: 2007, or another local equivalent if appropriate. Those following ISO 7730 and CEN Standard EN 15251 should provide the same level of documentation to meet the credit, including PMV or PPD calculations and an evaluation of 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).
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 by identifying an equivalent source of thermal comfort recommendations (from an industry group or a specialized ASHRAE design guide).
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. 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.
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. For spaces with metabolic rates below 1.0, utilize a tool like this one from UC–Berkeley rather than following the graphical method.
ASHRAE-55 was designed to accommodate activities up to 2.0 MET, but it’s possible to have higher MET levels in your project if you have a kitchen, fitness center, gymnasium, or warehouse. If this is the case, refer to LEED interpretation #10279 for guidance.
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 options:
According to the IEQ Space Matrix, spaces can be excluded from this credit if they’re non-regularly occupied and not normally comfort conditioned. For example, the storage area of a warehouse that’s accessed only intermittently is a good candidate for exclusion. However, any space that building occupants are expected to spend fifteen minutes or more at a time can’t be exempted.
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.
Our project is sewing factory It is not fully conditioned (A/C & Ventilation)
1.A/c for Office area
2.Fans (Exhaust, Fresh air, HVLS fans) for Production area
We use HVLS fans for lieu of A/c
Is it possible to attend this credit using HVLS fans in Ventilated Areas
HVLS fans are Circulating fans are not
awaiting for your reply
My project has apartments and penthouses on the top. Engineers design VRF with thermostat and residents can control their comfort thermally. I'm wondering how to document for this credit: do I just need to write a narrative that thermostat is available in every room and residents can control air speed, humidity, temperature to match their clothes and activities in the room so resident can have the best thermal comfort. Or I have to show PMV/PPD result for residents. If I have to do so, I will use thermal calculation tool for appartment as a whole or for every single room (bedroom, living room, kitchen room.
We have a fully naturally ventilated open cafeteria (No walls, only roof mounted on top of columns) that is occupied only for max about 2 hrs a day during 1hr lunch break and two tea breaks.
Do you think we should include this space in thermal comfort documentation or can we exclude it due to very low usage?
You are correct that this area may be excluded, but not for the stated reason. As described, the cafeteria is not an interior so ASHRAE 55-2004 does not apply. Section 2.3 states, "This standard specifies thermal environmental conditions...in indoor spaces designed for human occupancy..." I suggest you identify the space as exterior, explain the intended use and occupant expectations for an exterior cafeteria and this should satisfy the intent of the credit as well as the reviewer.
Thank you very much.
So how do you define an interior space? Have you come across any standard definition or is it a subjective judgement? For example if we have half walls instead of no walls at all, does that become an interior space? Or if we have 3 sides fully open with no walls and one side has a wall with standard window, is that an interior space or exterior space?
Each of the ASHRAE standards has a definitions section (Section 3) and typically words defined in this section are italicized. There is no definition for interior or indoor space in either ASHRAE 55 or 62.1, but 90.1 defines a space as a fully y enclosed space. Without walls, the area is not a space. Your description seems to align with what I would call a pavilion (with or without the knee walls) which is definitely exterior space. If there were folding solid doors that could be open, the space would be considered to be interior and you would have to include the space. If the doors were only there for security purposes during unoccupied periods, you could argue that the space is not enclosed when occupied.
Hi there, I'm working on a office project with Chilled beams and Displacement ventilationA system in which air slightly cooler than the desired room temperature is introduced at floor level and is lifted up by warmer air to exhaust outlets at the ceiling, increasing air circulation and removal of pollutants.. We are planning to do CFD simulations to analyse radiant temperature asymmetry , drafts vertical air temperature difference, etc. Would this be enough to document compliance with this credit?
I am dealing with a complex commercial center containing a indoor ski center and a ice rink, which clearly fall outside of the comfortable zone of ASHRAE 55. The feedback from GBCI required us to provide DESIGN strategies to improve thermal comfort and meet the intent of this credit. Does anybody know any design strategies that can be applied to ski center and ice rink?
Design recommendations for ice rinks are included in the 2015 ASHRAE Applications Handbook, Chapter 5 (as well as earlier versions), but indoor ski centers seem be too new/uncommon to have standard design recommendations. However, it would seem reasonable that the same criteria (or similar) would apply for both since they depend on keeping the space cold enough to maintain snow/ice and the occupants have an expectation of cold conditions within the space. Describing how the design aligns with the recommendations in the handbook or similar generally accepted standard should suffice. Also 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, although not specifically related to your issue touches on spaces that are not generally comfort conditioned. Keep in mind that different explanations may be required for spectator areas; the activity level is different and often radiant heat is provided for additional spectator comfort.
I agree with Cam that first looking for guidance from ASHRAE on what would be the standard of care for that kind of application. From personal experience with ice rinks or hockey arenas, it is all about humidity control. This is both for the ice and the spectators. Radiant heat works to help around the outside of the ice, but you have to control the humidity to feel comfortable.
I am dealing with a complex commercial center that contains a ski center and a ice rink, which clearly fall outside of the comfortable zone of ASHRAE 55. The feedback from GBCI requires us to provide DESIGN strategies to improve thermal comfort and meet the intent of this credit. Does anybody know any design strategies that can be applied to ski center and ice rink?
I am working on a project in Dubai, the design engineer has performed a psychrometric analysis using 46.0°C (DB) and 29°C (WB) for climatic design cooling conditions. The project space is cooling only, as there are no heating requirements in Dubai. How would this be documented on the LEED IEQc7.1 form? Would we use the dry bulb or wet bulb temperature for the cooling climatic design condition? Do we leave the heating design condition field blank, and write a narrative explaining the extreme climate where the project is located?
In a current project in Nigeria there's no heating requirement. We filled the cooling design condition in the heating section as well and commented this in special circumstances.This was ok for the reviewer.
The temperature that should be entered is the Dry Bulb temperature. A brief narrative including the average low temperature should confirm that no heating is required.
Thank you for the feedback Jens and Cam!
We wish to pursue the credits IEQ 7.1 & 7.2 , the space is auditorium seating with a dance floor for Wedding .(Area - 5300 sq ft , Occupancy 370 People), having office spaces on other floors . Location - Cincinnati Ohio
1. What MTR should to be assumed .? Not sure of the % time for standing, seating and dancing. My MTR is going above 2.0, How to show the thermal comfort in that case.
There is a cafeteria where the HVAC designer of record intends to have it naturally conditioned. According to ASHRAE 55-2004, naturally conditioned spaces must be equipped with operable windows that open to the outdoors and are readily adjustable by the occupants of the space.
The cafeteria in question is equipped wtih operable windows. Nevertheless, the resultant indoor operative temperature will likely be beyond the acceptable band in figure 5.3 of the standard.
Is supplemental evaporative cooling, which counts chiefly on fans, together with evaporation effect of water, construed as a viable alternative for naturally conditioned spaces?
Thank you very much in advance.
Recently, i am working for a complex commercial project including a ice rink and a ski centre.
These two spaces are acturally very special, whether we can exclude them when we consider thermal comfort ?
Leanne, to my knowledge there is no exclusions in the credit, even though ASHRAE 55 has definite limits. So if the space falls outside of ASHRAE, then you must demonstrate comfort in some other way, either by standard of care, studies that might substantiate conditions, or something else. You might find some industry standard that addresses what the standard of comfort is. However, this is not a sure thing at all.
But short answer is no, you cannot exclude any space to get the credit.
Maybe use this and build a custom ensemble with very high CLO ( thick jacket, long johns, etc.) http://smap.cbe.berkeley.edu/comforttool
I think with high CLO and high MET you can be comfortable even in cold areas. This tool might help make the case to the LEED reviewers but it only goes down to dry bulb temperatures of 10 degrees C/ 50 degrees F. http://smap.cbe.berkeley.edu/comforttool A mechanical engineer can probably get more into the logic behind all that. Definitely provide a written explanation of your strategy with your preliminary LEED design submittal. We've had to provide a lot of back up data on our projects with Natatoriums because of the unique space conditions.
I'm looking for clarification on how to handle air speed for floor 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. at the perimeter of a large lobby space. At these locations the air speed will be high but the majority of the lobby space and where most occupants are will be low velocity. Should the air velocity be based more on this area w/ most traffic/occupants rather than at the perimeter?
Also, there are large amounts of glazing and not sure if calculation of mean radiant temperature is typically required in such cases?
In lobbies it is often quite difficult to specify where people will be. I would position them in the most typical positions for the evaluation. This will then allow you to determine the velocity of the air where they are.
Radiant mean temperature is absolutely required, which is why you have most likely positioned 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. to be at the perimeter. So, you will have to evaluate that issue, and air is often difficult to provide this comfort. We have seen radiant floors used in heating climates to great affect in these kinds of spaces where more conventional radiation would not be allowed for aesthetic reasons. While I have not gotten to do this myself, I think the same floor tubing could be used to provide a cool slab in summer too, but you have to be very careful to control the temperature to stay above the dew point of the air. I have heard of this working in coordination with the air quite well, just not on a project that I have been directly involved with.
The project I'm working on is an ice-cream factory which will have staff working for short spells (but more than 15min) in spaces cooled to down to -40C. This is obviously outside the range of ASHRAE 55-2004 but I would like to know if it is still possible to get compliance if local regulations regarding workspace environments are met?
The project is in South Africa and there is a local regulation called the "Environmental regulation for workplaces" which is enforced by the Department of Labour. It specifies the amount of time that staff may work in sub-zero temperatures and the type of protective clothing that must be worn.
Do you know if this credit is achievable?
If so, how should it be done?
Many thanks for any advice you can offer.
Interesting question. This would definitely deserve a conference call with the reviewer team even before you submit. I know of cases where there are situations that ASHRAE 55 does not apply, and GBCI has accepted alternative ways or practices to show compliance. Your logic seems good, but having that conference call would be the best way to move forward.
You should also take a look at 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. Although it is primarily about spaces with elevated metabolic rates, it touches on compliance for spaces that are not normally comfort conditioned and could be helpful.
Short answer is that I think you cannot meet the credit.
We are looking for some advices on thermal comfort compliance upon IEQc7.1.
Our project is an industrial building with office and production spaces located in climate zoneOne of five climatically distinct areas, defined by long-term weather conditions which affect the heating and cooling loads in buildings. The zones were determined according to the 45-year average (1931-1975) of the annual heating and cooling degree-days (base 65 degrees Fahrenheit). An individual building was assigned to a climate zone according to the 45-year average annual degree-days for its National Oceanic and Atmospheric Administration (NOAA) Division. 6. There are heating and ventilation systems provided for the winter. For the summer it is designed that these ventilation systems to operate based on Outdoor air (100%) only. No cooling coils are provided. All spaces have operable windows, but without any control on their functioning.
While applying the ASHRAE Std. 55- 2010 Comfort Tool software, we are facing the following problems:
1.) Since there is no cooling system for the summer, the spaces presumably are understood as naturally conditioned. However we cannot use the 5.3. Optional Method as the building doesn’t meet all necessary requirements – the lowest outdoor temperature is -15.9 F and we have activities with MET>1.3. The question for this issue is: For the summer period, what space temperature should we enter in the Comfort Tool software and what MRT value?
2.) In the production spaces, the metabolic rate is greater than 2.0 MET. Is there some trade-off for these type of spaces and should we present the program output for them, although they don’t meet the requirements of the standard?
I hate to be a downer, but if you do not have cooling or active natural ventilation, then you cannot show compliance to ASHRAE 55. There are some methods to show intent (such as exercise areas where the MET rate is higher than ASHRAE covers), but if you are not going to do natural ventilation, then I would not pursue this credit.
For projects with MET over 2.0 you may use 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. The interpretation aligns with the "Use of Metabolic rate Data" on ASHRAE 55 2004 's page 17.
I have a couple of questions regarding this credit:
a) How can I convert the air velocity at the diffuser outlet to the air velocity reaching the occupant, knowing that an open plan office will have several desks and some occupants will be closer to the diffuser than others? Do I take average location in the middle of the room?
b) 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. for my project are located just below the ceiling level (around 9 feet above floor) whereas I need to report the air speed at the seating level of occupants (3 feet above floor). Do you think diffuser manufacturers will have these values / conversion formulas?
c) The Mechanical Engineer confirmed that this is a typical project with a typical HVAC design strategy. Can I assume that the air speed is 40 feet per minute (as a default value) without further documentation to the USGBC, given that they don't ask for any documentation?
For a typical project in an office building with typical HVAC design, yes, I believe it is probably acceptable to presume the air speed is 40 fpm.
If you want to analyze it more completely, then you can read the introductory information in a diffuser catalog like Titus to evaluate air flow patterns and throws / air velocity at various distances, heights, and supply air temperatures.
What ended up happening on your project? Did you have to provide justification for the 40 fps?
I am completing documentation for a dormitory that has a Summer/Winter operative temperature of 75/70, respectively. RH is 55, air velocity is 40 FPM.
Rooms with a 1.2 MET or lower are all noncompliant (or 1.2 MET and .5 CLO, which is also noncompliant). In order to comply, it appears my only options are to raise the CLO level or the operative temperature of the space (I think I can't change the activity level since, no matter what, the space use remains the same). Here are my questions:
1. Provided I supply a narrative stating clothing assumptions and these clothing assumptions are logical (not requiring occupants to wear a jacket in the summer, for instance) using the values provided for garments in ASHRAE 55, can I simply raise the CLO levels in the spaces (or come up with a 'standard' project CLO that passes in all spaces and I can then apply to each space for each season?)?
2. If I adjust the operative temperature of the space I'm assuming that if, for instance, I am cooling below the project setpoint we have designed to in order to pass, would I be required to provide calculations proving that the extra cooling required is achievable by the system and equipment provided in the space? The same question would go for spaces where the temperature required for comfort exceeds the design heating setpoint for the project.
3. Is it possible to adjust both values in order to change each as little as possible and remain as close to the ASHRAE standard number and the design 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. in the project? Would each assumption for CLO in the summer and winter have to be a global change, or can each space use a different CLO level even though they all exist within the same building?
Clo and MET level will be different for different space types. Adjusting these numbers based on a broad division of space types (classrooms, living units, kitchen,lounge/cafeteria, etc.) with a logical explanation is acceptable. Having the same MET level for the entire building is not an IEQc7.1 requirement.
Also, confirm the airspeed for the project as per design. 40 fpm is an upper threshold to ensure user comfort per ASHRAE 55 with exceptions for elevated airspeeds. However, it is not mandatory to use the 40 fpm in your calculations.
If you have to show compliance through different operative temperatures than what the design 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. are, I believe you will have to provide calculations confirming that the system is able to maintain those temperatures.
All other 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., besides the residential apartments, have been entered correctly using the thermal comfort tool. These spaces are mechanically ventilated. However, we received the following review comment:
"Please ensure all space types, namely the residential units, in the project building have been addressed in Table IEQc7.1-1 and that supporting documentation demonstrating compliance with ASHRAE Standard 55 has been provided."
This is my first time working on this credit and I am unaware how to demonstrate natural ventilation in the apartments using the thermal comfort tool. Is this possible? The apartments only have exhaust only spaces, such as the kitchen and bathroom.
I'm not sure why natural vs. mechanical ventilation would matter for the Thermal Comfort Design credit. The thermal comfort tool deals with temperature, humidity, etc. as well as the activity level and amount of clothing worn by the occupants. I believe you should be able to apply the thermal comfort tool in residential spaces without much difference from the way it is applied to your mechanically ventilated spaces. This credit has to do with mechanical conditioning, not mechanical ventilation. As long as you have heating and air conditioning in the residential units, it seems likely to me that you would be able to comply with the Thermal Comfort Design credit.
I agree with Julia. The thermal standard is not coupled to the ventilation standard.
Thank you both, Julia and Scott. This is very helpful. The reason I was thinking ventilation had something to do with credit documentation is because the credit form asks you to select if the building is mechanically or naturally ventilated so I assumed it needed to be accounted for. Why does this form request this information then?
That's a good question. I think the language in the v. 2009 reference guide is a bit muddled about the difference between natural ventilation and natural conditioning. There is a reference to Section 5.3 of ASHRAE 55-2004, but that section deals with natural conditioning, not natural ventilation. I think as long as you have mechanical *conditioning*, that for version 2009 the natural vs. mechanical ventilation should not matter. This is especially true in a residence where the required amounts of ventilation are tiny. I suppose a reviewer might question the impact on comfort if one is depending on natural ventilation for a high occupancy space, but that would be more applicable in a non-residential usage and also may come into play more in LEED v4 from what I have heard.
We have a project where design mandates space usage as manufacturing facility with met rates of 2.2, clo values of 0.6 and air velocity of 120 ft/min or 0.6m/sec. Well, ASHRAE 55-2004 mandates that PMV approach cannot be applied for air speeds higher than 40ft/min (0.2 m/sec) and refers Section 5.2.3 (Elevated Air Speed) for compliance. Unfortunately, section 5.2.3 also limits clo values (0.5-0.7) and sedentary activity (1.0 to 1.3 met rates). It appears, both PMV and Section 5.2.3 approach do not apply.
So, how do we demonstrate thermal comfort compliance for scenario where we have high metabolic activity (2.2) and high air speed (120 ft/min or 0.6 m/sec)?
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 has some interesting discussion as well.
Mayank, the 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. you found is a good one. I would also direct you to the guidance shown in the FAQ above on the LEEDuser website (under Bird's Eye View—content for members).
Hi, we are doing a project in South east Asia for LEED NC. We are planning to maintain the indoor operative temperature of the building at 77 deg F as against 75 deg F as per ASHARE thermal comfort design.
We are doing so; as the other existing buildings of the same organization has been maintaining the indoor temperature as 77 deg F for the past one year in response to save energy and have not received any complaints from the occupants. The organization is also planning to make this as their company’s policy in order to conserve energy. Will this be compliant for the IEQ C 7.1 ? What would be the supporting documents that would be required to substantiate the same?
I suggest you try using either the ASHRAE comfort tool software (available at ashrae.org for about $99 last I checked) or the CBE comfort tool available free. By entering a lower clothing insulation level (clo) and other variable values more typical of southeast Asia, you may find that 77 degrees does indeed fall within the comfort window.
From posts below:
"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.
On past project we have been told: Please note that Figure 18.104.22.168 can only be used when air speeds are less than 40 feet per minute.
We have a project with air speeds at 40 fpm. So does that mean we can't use Figure 22.214.171.124.? Or is it just above 40 fpm? Thanks!
The air speed cannot be greater than 40 fpm. This is stated in the third paragraph of Section 126.96.36.199.
No : this § states that the figure 188.8.131.52 does apply when the air speed is below 40fpm. Section 5.2.3 states explicitely that "this standard allows elevated air speed to be used ... under certain conditions", whereas section 184.108.40.206 explains how to deal with these conditions. I encourage you to download the addendum b of the 2007 version or to buy the 2013 version, since all this parts have been deeply updated.
So we can or can't use Figure 220.127.116.11 for air speeds of 40 fpm?
It will depend on the version of the standard you want to use and to the interpretation you will make. Shortly :
- 2010 version without addendum b : "figure 18.104.22.168 specifies comfort zone for environments ... and where the air speeds are not greater than 40 fpm"
My understanding is that 40 fpm complies with this statement.
- 2010 version with addendum b : the statement "and where the air speeds are not greater than 40 fpm" is deleted.
- 2013 version : (§5.2.1 becomes §5.3.1) "Average air speed greater than 40 fpm requires the use of section 5.3.3".
My understanding is that 40 fpm does not require the use of section 5.3.3 (and therefore allows to use the figure 22.214.171.124, renamed 5.3.1 in the 2013 version)
USGBC allows you to use the standard "with errata but without addenda". My opinion is that you can choose to use errata if it is better for you, but then you will have to use all of them (which is rather handsome for the 55.2-2010 ...) or it's more simple to use the 2013 version.
I hope it will help
Thank you Serge. Yes I agree sounds like I can use 126.96.36.199 because it does that speeds GREATER then 40fpm and 40 is not greater then 40 :)
I am happy that LEED is accepting ISO 7730 and EN 15251 as alternative to ASHRAE 55. My problem is that there are no single requirements in these standards but examples / recommendations for design parameters for 3 different categories of comfort.
In IEQp1 we are requested to meet the minimum requirements for ventilation. I would assume this is true for IEQc7.1 as well, and choose the least category. Does anyone have experience with submitting this credit following ISO / EN?
Yes, we did it successfully using the ISO 7730 Appendix E and justifying by complete thermal simulation that PMV was never out of the interval -.5, +.5 for all rooms and all occupancy conditions.
We seek some advice on how to demonstrate thermal comfort compliance for 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. in an industrial warehouse type space in Christchurch, New Zealand. There is heating provided for winter comfort . Natural ventilation provides fresh air throughout the year and passive cooling during summer. There is also mechanical ventilation for air movement only available during summer. As this is an industrial type building the space is nor normally comfort conditioned we throught that the 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. ID#10279 is appropriate as follows:
"Spaces that are not normally comfort conditioned can only be excluded if they are non-regularly occupied. 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. that are not normally comfort conditioned, and not able to meet the ASHRAE 55 thermal comfort conditions, the project team must 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"
Our question is what do we need to demonstrate compliance with this alternative compliance approach? Is it simply a case of saying we have heating during winter and air movement during summer?
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.
This brief guide introduces some of the key variables involved in designing for thermal comfort.
Principal & Founder
The Green Engineer, Inc.
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.
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