Spray-foam insulation is gaining popularity these days, and for good reason. Not only does it offer lots of R-value per inch, but it also air-seals the house. I’ve been building custom homes in North Carolina for more than 20 years, and I’ve been using spray-foam insulation for the past four. These days, all my projects get 8 in. to 12 in. of foam under the roof deck, and I often use foam to insulate walls and crawlspaces as well.
Prepping for the spray-foam crew is now just another part of the building process, but it took some time and a lot of stained shingles and concrete for me to figure out the learning curve. Along the way, I discovered that the first hurdle in using spray-foam insulation might just be working with the building inspector.
Venting, fire safety, and building officials
The first time I insulated an attic with spray foam, the building inspector asked me to supply a letter from my structural engineer stating that the roof framing was strong enough to support the weight of the foam. That might have been the most extreme case of an inspector being misinformed about the properties and benefits of spray-foam insulation, but it wasn’t an isolated case.
Code officials in my area value ventilation in attics and crawlspaces so much that they have a hard time with the thought of sealing these areas with foam. So if I’m planning to spray the underside of a roof deck or a crawlspace, I talk to the building inspector during the permitting process to make sure he’s OK with not venting either space.
The most common speed bump I run into during these conversations involves roof venting and shingle warranties. If the spray-foam insulation will void the…