The reference guide is clear that 14,000 CFM of OA per SF (that is >60deg and
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NC-2009 IEQc3.2: Construction IAQ Management Plan—Before Occupancy
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Purpose behind the 60% RH parameter?
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Allison Beer McKenzie
Architect, Director of SustainabilitySHP Leading Design
LEEDuser Expert
646 thumbs up
March 9, 2016 - 9:21 am
Other areas of LEED (especially in LEED for Schools) indicate that RH of over 60% creates greater potential for mold growth, so I have always assumed that is what is behind the 60% RH requirement, but I don't know that to be fact.
I have also also assumed that 60/60 applies to Path 1, Option 2 as well, but also do not have concrete proof of that. Keep us posted on how it goes! We have steered clear of this credit (or opted for testing) in many case because of being in humid Ohio.
Erin Holdenried
Sustainable Design DirectorBell Architects
45 thumbs up
April 12, 2016 - 9:28 pm
@Landry, did you submit your project? How did the reviewer respond?
I have a project in a similar situation, though in a cold climate where 60 deg F cannot be maintain for one of the zones. The spaces served by this AHU are mechanical rooms and unoccupied. The system is designed to maintain a 55 deg F in the winter. As this area is unoccupied and humidity control will not be an issue, would the reviewers accept a lower temperature for this zone?
Lyle Axelarris
Building Enclosure ConsultantBPL Enclosure
64 thumbs up
April 12, 2016 - 9:48 pm
Temperature control is often a challenging part of this credit for us in Alaska. The 60%RH requirement makes sense to me, but I don't get the 60F requirement. Any insight would be appreciated.
Also, how do you guys show 60/60 compliance? I've been asking contractors to log temp/RH in the return air via the DDC, but does the reviewer really need to see thousands of hours of data?
Landry Watson
Assistant Vice President - SustainabilityAlexandria Real Estate Equities
29 thumbs up
May 4, 2016 - 5:54 pm
UPDATE - Submitted credit and as expected was set to pending/denied with the following comments. "Please provide an hourly log of the interior RH/Temp to demonstrate compliance throughout the flush-out process". So, I set up a conf. call to discuss with GBCI and I got some additional information -- and please be gentle in quoting since I'm paraphrasing here - GBCI Response/Guidance - Project flush-out that violate the 60/60 guidelines "a couple of times" will be considered on their merit and documented corrective action. So...what we can deduce here, is that ultimately a project must provide a log of RH/temps throughout the flushout to demonstrate compliance (not surprising, since the Ref guide tells us that). What I further dug into with GBCI is that they DO agree that Mech systems provide a component of dehumidification; however, it was not provided what % that they considered reasonable. AND...it was further determined that without a log, that GBCI uses any number of local weather station (NOAA or other) archives to simply back check the potential of maintaining 60/60 conditions at a given OA rate that you are indicating to achieve flush-out. BOTTOM LINE: Keep a log.
Hybrid approach with Path 1&2 was not an accepted approach if the 60/60 parameters appeared to have been violated more than "a couple of times" and there was no log to contradict weather conditions during your flush out dates.
And...60/60 parameters apply to both paths.
Lyle Axelarris
Building Enclosure ConsultantBPL Enclosure
64 thumbs up
May 4, 2016 - 7:56 pm
Very useful information, Landry. Thank you!
Regarding your mech system dehumidification comment, it sounds to me like you may be measuring temp/RH in the supply duct. I have always felt that the return ducts are a more accurate sensor location to represent indoor air conditions since the supply air is tempered quite a bit by indoor conditions (latent heat, etc.). For example, cooling air at discharge point could be set to 55F in order to maintain 70F for thermal comfort. Often for me, the air is for ventilation only, with heat provided by radiant slabs for example, so return air temp/RH is more indicative of what the "room air" conditions are.
Does that sound reasonable to you?