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Documenting standard practice
EQc7.1 requires that HVAC designs meet the requirements of ASHRAE Standard 55-2004, which deals with thermal comfort of building occupants. Specifically, ASHRAE 55 requires project teams to address air temperature, radiant temperature, humidity, and air speed. Earning this credit also sets the stage for you to earn EQc7.2: Thermal Comfort—Verification. In most cases, designing a system that complies with ASHRAE-55 is standard practice and documentation is the only LEED-specific requirement for achieving the credit, so it should cost very little to earn.
Natural ventilation and certain occupancies make it tricky
Meeting this credit in naturally ventilated spaces is tricky, because it’s hard to ensure that thermal conditions remain within...
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15 Comments
Multi family residential
We were denied this credit in a residential application recently although our approach has previously been acceptable on similar projects. The review language includes,
"Specifically, the preliminary review comments requested documentation confirming that the system was capable of meeting the humidity setpointsSetpoints are normal operating ranges for building systems and indoor environmental quality. When the building systems are outside of their normal operating range, action is taken by the building operator or automation system., and providing the peak heating and cooling loads when the windows were open to 4% of the floor area during peak heating and cooling conditions. However, the documentation shows an infiltration rate of only 0.35 Air Changes per Hour, which does not appear to represent the level of infiltration anticipated to occur during peak heating and cooling when a window area corresponding to 4% of the floor area is open."
Our team provided documentation verifying humidity setpoints were met, but we are particularly concerned that we need to demonstrate that our system is capable of dehumidification, heating and cooling with all windows open. Has anyone run into this review issue before? Is there any suggested guidance?
Thermal Comfort credit 7.1 - Version 2.2
How can you achieve compliance with Ashrae 55 with occupants having activitties outside of of the range in the graphics method section 5.2.1.1.
This for an exercise rooms with metabolic rates from 3.0 to 4.0?
Since no response has been posted, I'll chime in.
You should look at the proposed activity levels over a period of time including cool-down periods and rest breaks. If the time weighted average of the various metabolic rates is below 2.0 met,the predicted mean vote (PMV) method in Section 5.2.1.2 may be used.
Dehumidification on cool days?
Our v2.2 multi-family project has standard split system mechanical units, with operable windows. We documented compliance with ASHRAE 55-2004 and received the following comment:
"Please provide a description of the system’s ability to maintain the maximum humidity levels during periods of low cooling load or a justification for no dehumidification strategy based on the local climate conditions."
As the project is located in DC, it's technically possible to have humid days when no cooling is required (so the mechanical units will not operate). However, this is the first time we've encounted this comment. Adding humidistats to the units is very expensive. Any thoughts on how to respond?
Controlling humidity loads at part load conditions is one of the key goals this credit tries to accomplish, so the reviewer is correct to ask for more details.
You need to show how the building maintains comfort conditions year round, not just at design conditions.
Generally we show psychometric charts of cooling coil operation at part load conditions, demonstrating that appropriate space conditions can be maintained. For package equipment with high outdoor air loads in humid climates it may be difficult to meet these requirements.
Design Air Speed
What does the design air speed refer to?
You'll need to look at ASHRAE 55-2004, but in general it's the velocity of the air (from the supply diffusersIn an HVAC context, diffusers disperse heating, cooling, or ventilation air as it enters a room, ideally preventing uncomfortable direct currents and in many cases, reducing energy costs and improving indoor air quality (IAQ). In light fixtures, diffusers filter and disperse light.) to which a person is exposed.
So that would be roughly 50 fpm based upon the manufacturer's data and ASHRAE? Or how is that determined?
Yes, manufacturer's data, ASHRAE, modeling, could all help you determine this value.
EQc7.1 narrative
For years I have seen this credit documented without any issues. Recently the reviewer asked for the following supplemental information:
"Please provide a narrative that describes the design strategies used to deal with discomfort from drafts and radiant temperature and the calculations used to determine the comfort zone including clothing allowance and activity level."
We believe we are meeting the credit requirements with the initial documentation provided but are a bit unclear about how to respond to this request. Additionally, achievement of EQc7.2 is dependent on first meeting EQc7.1, so we want to ensure we meet.
Has anyone experienced this type of comment? Any feedback and/or guidance is most appreciated.
I too recently received a similar comment. The comment received on our project was "Please document the comfort parameters used in the calculation of design temperatures, including clothing, metabolic rate, and indoor air speed." Comment goes on to request supporting calculations and description of any local discomfort affects that may be present. Our team was caught off guard by this and we feel we meet the intent. I'm preparing my re-submittal, so if anyone has any guidance I would appreciate it too!
Carlie - I just read through all the info on this website (including the Resourses section) and it was very helpful. Sounds like they want results of calculations that determine the comfort range and the assumptions used in the calculations. We can't simply assume since we fall into the chart in ASHRAE 55 (75F/50% RH in the summer, for instance) that we meet the credit.
Carlie,
I have the very same comment on a Leed for Schools 2007 project. Can you tell me how you addressed this comment...and if it worked?
IEQ C7.1 documentation
I have a warehouse bldg. w/ internal offices. I am conditioning the offices but only ventilating the warehouse area & am unclear about documenting my compliance.
For the warehouse, I will review the CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide's.
For the office spaces: is it sufficient to merely use the graph (ASHRAE Std 55-2004, Figure 5.2.1.1)? Pposting your calculated space conditions can indicate that you are within the acceptable range & do comply.
Documenting this credit is a bit more complicated than just checking that one graph. We have step-by-step suggestions in the Checklists tab, above.
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