Spray foam insulation beats fiberglass batts because it seals air leaks completely. Fiberglass lets cold air stop just half an inch from your interior, and any nail through the vapor barrier creates a draft pathway. Spray foam fills the cavity airtight, so fasteners don't compromise the seal.
Okay, today we're going to compare spray foam insulation against some other insulations. We'll look at 2 different wall assemblies with 2 different types of insulation. Both of these assemblies, we got outdoor space here, indoor space here, outdoor space here, indoor space here. In this assembly, we've got fiberglass insulation and a 6 mil vapor barrier installed on the inside. On this one, we have 3 inches of spray foam insulation. The really nice thing about spray foam is when you got cold air outside the building, it stays outside the building. It's not able to penetrate the spray foam insulation at all. In a batt and poly system, it's able to penetrate into the batt insulation and then stops at your vapor barrier. So what that means is that the cold air inside the wall assembly is actually only a half an inch from the inside of your home, so there's very little stopping it there. Another important thing is if you're hanging pictures or a television on either of these walls, You have to puncture your vapor barrier in this system, which now is going to allow cold air to get into the home or allow warm air to get out. However, in a spray foam insulation system, when you put that nail in, you can see there's a nice big gap in between the spray foam and the nail, and it's not a problem at all. Even if this wall was completely full of insulation, you're never going to penetrate the full depth of it and have those same issues. And so that's why spray foam insulation is the best for your home.
