Most installations of spray foam insulation, when properly installed, act as an air barrier. When you use it instead of the fluffy stuff (fiberglass, cellulose, cotton), a house will be more airtight. That’s good.
When a house is airtight, the nasties in the indoor air tend to stick around. Volatile organic compounds (VOCs), water vapor, odors, radon, and other stuff you don’t want to immerse yourself in make the home’s indoor air quality worse.
How do you solve this problem? Mechanical ventilation. Well, source reduction and separation would come first, but airtight homes need mechanical ventilation.
The role and responsibilities of spray foam contractors
If I were a spray polyurethane foam (SPF) insulation contractor, I’d do like they all do and make sure that every potential customer I talked to knew about SPF’s air sealing qualities. (I would not, however, try to sell people on fantasy R-values of 20 or 40 per inch, which I have known some SPF contractors to do.)
Then I’d do what not nearly enough spray foam contractors do: I’d tell all my customers they need to install a mechanical ventilation system in every new home with spray foam. In fact, I’d include mechanical ventilation as one of the things I sell. (Maybe that’s just because I’d rather be an HVAC contractor, though.)
If a client didn’t want me to do the ventilation, I’d have them sign a liability waiver acknowledging that they have been informed about the importance of mechanical ventilation in airtight homes. Then I’d have that piece of paper so I could pull it out if the homeowner ever came after me for poor indoor air quality.
I’m not the only one saying that ventilation needs to be part of new homes with spray foam insulation. Recently, Mac Sheldon of Demilec emailed me about this issue and wrote, “I’m telling… preaching… admonishing… SPF contractors to never pull the trigger on a spray foam job until there’s a ventilation plan in place.”
I believe that spray foam insulation can be an effective product to use in building enclosures. I also know that spray foam can be done poorly. No matter which way it’s done, however, mechanical ventilation is not optional in airtight homes. I wonder how many spray foam contractors will find that out the hard way.
Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. Check out his in-depth course, Mastering Building Science at Heatspring Learning Institute, and follow him on Twitter at @EnergyVanguard.
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