Low-VOC mastics and mold growth

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Author Message Joel McKellar, Assoc. AIA, LEED AP Senior Member Username: joelmckellar Post Number: 15 Registered: 02-2006 Posted on Tuesday, February 05, 2008 - 05:19 pm:    One of our consultants recommended the use of solvent-based (aka high-VOC) duct mastic only. He claimed other mastics have a tendency to foster mold growth, which would certainly negate the IAQ benefits among other problems. This will mean losing the EQc4.1 point though, and I'm hoping one of you may have encountered a product that would solve this problem? Thanks! Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 719 Registered: 07-2002 Posted on Tuesday, February 05, 2008 - 06:05 pm:    some Kaiser Health Care systems are requiring the use of solvent based adhesives for floor installation for much the same reason -- the mold growth issues with the flooring were simply causing too many problems. however, if you look at the credit (I'm using the version 2.2 reference) the VOCs allowed for "other" sealants can go as high as 420, which may allow a lot of other products, including some two part solvent based ones. Carlisle makes a couple of solvent based ones that are at 395 VOCs, so they meet the standard. remember also that the IAC credits are generally arrived at by averaging, so there is an allowance for some small quantity of really stinky stuff on the project. the contractor needs to adequately ventilate the installation space. Anonymous   Posted on Wednesday, February 06, 2008 - 04:45 pm:    I would challenge the "consultant" to produce one single bit of credible evidence in support of such a claim. One of three things required for any mold growth is water (food source and hospitable temperature are the other two). Is the building being designed so that the ductwork is continually, or even sporadically, wet? Doubtful. Mold can grow on anything. Glass, aluminum, plastic, - even solvent based adhesives! The food source for many of these materials is deposited in the form of dust, usually airborne. There could be a food source within a particular adhesive, solvent or water based, and/or a food source could be introduced (dust, for example). Lstiburek has done quite a bit of debunking on this issue. He has a lot of valuable information on his website buildingscience.com and is also available as a consultant.