We have a project that has failed an IAQ test by exceeding TVOC levels. The team would like to flush the space with outside air prior to retesting to improve the result, however outdoor air quality is poor and we're afraid it could contribute to another failed test. Is there a protocol to take outdoor air contamination into account when performing indoor IAQ testing?
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Tristan Roberts
RepresentativeVermont House of Representatives
LEEDuser Expert
11477 thumbs up
January 9, 2013 - 9:03 pm
Norma, that seems like it would be extremely complex from a scientific and methodological perspective. I'm wondering what the intent of such a protocol would be. To ascribe certain contaminant levels to outdoor air, and thus hold the LEED project harmless for them? Hard to see how that would work. Could you filter the air effectively?I suppose you would do this if it were an option, but simply following the flush-out procedure would be the easiest path to earning the credit at this point.
Norma Lehman
PrincipalThe Beck Group
133 thumbs up
January 10, 2013 - 10:29 am
Thanks for the response, Tristan. The project is using a variable refrigerant flow system for HVAC. Our MEP estimated the flush to take about 9 months since it's a low volume system. We thought perhaps we could subtract the outside TVOC levels or take a percentage from our interior levels.
Allison Beer McKenzie
Architect, Director of SustainabilitySHP Leading Design
LEEDuser Expert
646 thumbs up
January 10, 2013 - 10:38 am
Since you are still using the testing methodology, the flush out parameters are less restrictive as far as air temperature and humidity control than if you were using the flush out method. Would it be an option to bring in some temporary fans to expedite the flush out?
Dylan Connelly
Mechanical EngineerIntegral Group
LEEDuser Expert
472 thumbs up
January 10, 2013 - 12:17 pm
Norma,
I'm confused about how your ME arrived at 9 months for the flush out.
VRF systems still need to provide a minimum outside air to the space, usually this is achieved through the use of a dedicated outside air system (DOAS).
Let's say you were providing 0.15 CFM of OA/SF (California T24 Ventilation Minimum for an office space), the calculation would go like this:
0.15 CF/min per SF * 60min/hr * 24hr/day = 216 CF/day per SF
You can go Path 2 (phased flush out), which requires 3,500 CF/SF. At 216 CF/day it would take 16.2 days to complete. 16 days can definitely be impossible to fit in a tight schedule, but the 9 month calculation is unheard of for this credit. Even if you were providing half the CFM of OA/SF that is required in California (closer to the ASHRAE calc), you'd be at 1 month for Part 1 of Path 2.
During the occupied period, I could see there being an issue with supplying the 0.30 CFM/sf of ventilation required for Path 2 with your DOAS, but that's another story.
Norma Lehman
PrincipalThe Beck Group
133 thumbs up
January 10, 2013 - 12:40 pm
Excellent point, Dylan. I've been brought on to the project at the end to seal up the LEED construction documentation and am not sure how the MEP came to the flush rates. I'll check with the rest of the project team. Unfortunately, we're now too late for the flush process because of phased occupancy. We'll try Allison's approach and hope for the best!
Norma Lehman
PrincipalThe Beck Group
133 thumbs up
January 10, 2013 - 3:00 pm
To follow up on my last comment, I asked the team and it seems the 9 month flush process incorporated the occupancy phasing which began in 2/2012.