After reading an article by Joe Lstiburek titled Just Right and Airtight, I got to thinking about what we've been spending a lot of time on lately, and that is what we call the “New Big Holes.” Of the 350+ spray foam encapsulations we have tested with a Blower Door and infrared (IR) camera, it's safe to say there are lots of “New Holes” being created from incomplete spray foam installations. It also reminds me of Allison Bailes's article, Infiltration Occurs at the Surface, Not in the Volume. The problem is you gotta know your surface!
I agree the Blower Door may not be needed to find those “Big Holes” Joe writes about, but these “New Holes” in spray foam installations cannot be found otherwise. Whether it's closed-cell or open-cell spray foam, the foam leaves the applicator as a molten liquid and expands rapidly once it hits the surface to which it is applied. As this chemical reaction occurs, the rapid expansion leaves opportunity for pockets, or holes, to be formed and not seen. The holes are not “in” the foam itself, but behind it, beside it, around it, or covered by it. Most of the time, they're hiding!
Foam inherently is not smooth, so it is not easy to know which lump is covering a hole from a visual inspection alone. We have been finding these bypasses by running the blower door and using an IR camera to go and search for these breaches. Some are dime-sized, some are apple-sized, and many are larger.
Sometimes the foam looks perfect, but there's a space between the top plate, and the foam coming down from the roof deck. There are times the envelope edge is completely missed and even times when the old fiberglass batts have not been removed and the foam is sprayed directly on top of the pink stuff, creating a deceivingly incomplete attic encapsulation. You can't find these holes from a Blower Door number alone. You have to search for the air with the Blower Door running and by using smoke, IR, and your hand to discover the breach.
These “new holes” can form anywhere, but mostly we're finding them near the top plates, at hip rafters, below kneewalls, and around architectural details in the building envelope. These bypasses in spray foam insulation are the cause of mysterious problems that HVAC contractors have to fight. To date, we have helped many homeowners who were experiencing problems with high humidity, condensation, mildew, and other problems in their newly spray foamed attics and homes.
The clients we've helped had no idea the problems were related to the foam’s incomplete seal. They got to us after the HVAC contractor had done all they could to hold the problems at bay, many times adding a dehumidifier to the space. Here in Savannah, GA and Hilton Head Island, SC, allowing humidity and ambient air to infiltrate into the home and get trapped in the newly (almost) encapsulated attic is a problem. This warm, moist air normally exhausted out of the ridge vent, but is now trapped and allowed to migrate into the home’s materials and indoor air. This problem is eluding many, if not most, of the spray foam insulators we know, and probably is happening in your area too.
I do believe in foam and live in a spray foamed home. Spray foam is a great product, but it is not a magic product. It takes a skilled operator and needs to be tested to make sure that the job gets done properly. The bottom line is, what you see is not always what you get, so have your job tested and don’t just pay attention to that ‘target’ blower door number, look for the holes that may cause problems before they find you.
by Jamie Kaye of Elm Energy Group in Hilton Head, SC. Jamie is a certified HERS rater (with Energy Vanguard Energy Ratings as his provider), BPI Building Analyst, Level 1 Thermographer, juggler, and all-around great guy. I met him a couple of years ago when he took the HERS rater class, and we got to juggle together every day at lunch. I'm sure he'll be one of the very first certified Home Energy Jugglers.
Photo credits: All insulation photos by Jamie Kaye.