LEED IAQ Ventilation Compliance

asked 2024-08-02 12:14:05 -0600

updated 2024-08-02 12:15:06 -0600

Have a trend of receiving the LEED review comment "the proposed model's ventilation exceeds 62.1 code and the baseline ventilation must be reduced to meet code or 62.1. Model must match the LEED's IAQ calculator." While in some cases there is a increase in ventilation by the mechanical designer, I've found the IAQ calculator to be (significantly) deficient on a few fronts.

First certain exhaust only spaces such as restroom and locker rooms are missing from the IAQ calculator. In many cases, these zones may be 100% OA in our designs to avoid smells or IAQ issues. Ventilation standards include requirements around supply OA AND exhaust - thus this is missing a key part of the equation.

Secondly, some exhaust only spaces which are included such as Kitchens or Science Labs have laughably low & incorrect rates. Science labs at 0.17 CFM/SF or Kitchens at 0.33 CFM/SF vs 62.1-2010 required 1.00 or 0.70, respectfully.

Third there are requirements in 90.1 regarding leveraging transfer air for exhaust, specially for Kitchens. This complicates the ventilation calculation & air balance further since Kitchens per Appendix G are typically split to their own zone due to load density.

My team has made efforts to model the Baseline lower at a code minimum, but am still receiving the same comments that rely on flawed IAQ calculations. So - how do you handle Proposed vs Baseline Ventilation?

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answered 2024-08-02 23:24:52 -0600

Keigo
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updated 2024-08-04 05:58:48 -0600

I don't think the IAQ calculator is significantly deficient.

Exhaust only spaces such as restroom and locker rooms are not found in the IAQ calculator because they are not listed in ASHRAE 62.1 TABLE 6-1 MINIMUM VENTILATION RATES IN BREATHING ZONE. They are unoccupied spaces. EQ Prerequisite Minimum indoor air Quality Performance and the IAQ calculator are for occupied spaces. OA flow rates in unoccupied spaces do not need to be added to the IAQ calculator and the Minimum Energy Performance Calculator (MEPC). If you want to add the OA flow rates in unoccupied spaces to the MEPC dut to the energy consumption of precooling/preheating the OA, please explain the difference in the total OA flow rate between the IAQ calculator and MEPC to GBCI.

I don't see the numbers 0.17CFM/SF for Science labs and 0.33CFM/SF for Kitchens in the IAQ calculator. The OA flow rates in the IAQ calculator are 0.43CFM/SF for Science labs and 0.27CFM/SF for Kitchens with default zone population. Rp and Ra in the IAQ calculator are consistent with those in ASHRAE 62.1 TABLE 6-1.

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The minimum OA flow rates in TABLE 6-1 are for occupants. If you have local exhausts such as Fume hoods in Science labs to remove pollutants and Range hoods in Kitchens to remove odors, those local exhausts (and the makeup air supply fans, if any) are regarded process loads. In the Baseline case, the process loads should be modelled identically to the Proposed case. The makeup air (outdoor air or transfer air from the other zone) does not need to be added in the IAQ calculator.

1.00CFM/SF for Science labs and 0.70CFM/SF for Kitchens are the values in ASHRAE 62.1 TABLE 6-4 Minimum Exhaust Rates. TABLE 6-4 is irrelevant to EQ Prerequisite Minimum Indoor Air Quality Performance and EA Prerequisite Minimum Energy Performance.

Supplement to answer your comments

In LEED, Nonregularly Occpied Space is a more accurate description than Unoccupied Space for restrooms and lockers. I apologise. The definition 'an area that people pass through or an area used for focused activities an average of less than one hour per person per day' and the examples are in the LEED Reference Guide for BD+C: LEED V4. However, this classification misleads addressing your original questions, so please ignore it. Whether the Occupancy Category is listed in ASHRAE 62.1 TABLE 6-1 MINIMUM VENTILATION RATES IN BREATHING ZONE or not - that's all. If the Locker rooms in your project are used mainly for meetings for hours rather than just for changing clothes, you may need to select a different Occupancy Category such as Conference / meeting in the IAQ calculator in contrast to the space name shown on the floor plan.

Please do not confuse Ventilation with Exhaust. Ventilation requires outdoor air, but Exhaust does not necessarily require outdoor air (e.g. transfer air is allowed). ASHRAE 90.1-2010 G3.1.2.6 is ... (more)

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Thank you for the thorough answer, however I’m curious about specific parts of your answer.

dradair ( 2024-08-03 14:32:18 -0600 )edit

First, classifying restrooms and locker rooms as unoccupied spaces doesn’t align with those space use types. Locker rooms in an athletic training center(s) or a stadium are most definitely occupied - despite how LEED classified it.

dradair ( 2024-08-03 14:32:26 -0600 )edit

Second, these space types are covered in 62.1-2010 under Section 6.5 Exhaust Ventilation. How is Table 6-4 irrelevant to the EA Prerequisite Minimum Energy Performance when the requirement in 90.1-2010 G3.1.2.6 (c.) states that when ventilation exceeds the minimum in the Proposed the Baseline must go back to the “rating authority or building official”? Based on LEED review comments, this falls back to 62.1-2010. In 62.1-2010 Section 6.1 is very clear that for compliance any of the 3 ventilation methods and the Section 6.5 for exhaust must be followed for compliance.

dradair ( 2024-08-03 14:32:48 -0600 )edit

Lab hoods should be an easy argument to make to GBCI regarding classification as a process load. But for kitchens and locker rooms that are in Table 6-4, have you had success classifying those as process loads based solely on that space use type not being the in IAQ calculator? 90.1-2010 Tale 6.5.7.1.3 limits hood CFM based on type & use, but there isn’t such a table for Locker Rooms or Labs.

dradair ( 2024-08-03 14:32:57 -0600 )edit

Note – I found the issue with my ventilation rates in the IAQ table. Hadn’t accounted for population and still have Ez=0.8. Make population= and Ex=1 and I get the proper rates. Mia culpa. sorry for 5 comments.....silly character limits

dradair ( 2024-08-03 14:33:24 -0600 )edit

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