Addition Insulation

Two things keep a building from losing heat (or coolth) to the outside: insulation and lack of leaks. Plugging leaks is more important (you get more benefit for what it costs) but caulk isn't very exciting to photograph or talk about. Suffice it to say that as we built the addition, we ran a bead of caulk in every joint. Between the foundation and the bottom of the walls, for instance. Where the doors and windows connected to the walls, too. We even caulked the sheets of Tyvek housewrap together.

Now insulation, that's another matter. What we did was pretty exciting—foamed in place. You might remember that we staggered the studs in the exterior walls. This allows the insulation to be continuous, zig-zagging around the studs. No thermal break, they call it. It took the insulation crew several days to complete the job. Spraying the two-part chemical is rather messy, so they wrapped all the beams in plastic to keep them clean. When they spray it, you can watch the foam expand, a little slower than the stuff that comes in a can, but plenty fast.

The foam comes in two kinds, open cell and closed cell. Both are excellent insulators, and they both also make a pretty good seal (—as if caulking weren't enough. We have a very tight house). The open cell is a little more flexible—it's less likely to pull loose when the house bends; the the closed cell insulates better. And it costs a lot more. We elected to put closed cell under the roof and open cell in all the walls. You can see the foam squooshing out behind a stud in the picture. We told them to get the cavities completely full, and they did a really good job, in our opinion. When they were done, you could see every other stud, and the space was full. As it happens, they missed one hard-to-reach space in a corner behind a post, but I filled it up with expanding foam. Took a whole can. That's the corner in the picture.
Those pieces of lumber are parts to a yurt. More on that in a future post.
The difference in the temperature of the addition was remarkable. It was high summer when they insulated and the addition went from sweatbox to retaining the night's coolness all day.
Now on to the paint job and the deck!