We've been pretty busy around here, but I have a few progress pictures to show. The insulation has been installed in the ceiling of the upper garage bay, and the cathedral ceiling of the room above it.
What we ended up going with is about 2" of closed-cell foam sprayed on the backside of the roof decking and the sub-floor. Closed-cell foam is about R8 per inch, and it completely seals the surface from airflow and vapor.
This is what the spray foam looks like after it dries.
The remaining space in the cavities between the rafters and floor joists was filled with fiberglass batts. R30 in the new living area ceiling, and R19 in the upper bay ceiling. This seems to be a good solution that kept the costs within reason, and accomplished what I wanted.
I also installed insulation in the roof area behind the gable before closing it up.
Aside from the obvious need for insulation in the roof over the new living area, I wanted to reduce the drumming noise the floor was making when walking on it. Both goals were achieved, and we're very happy with the results. The floor is much, much quieter now, and the room no longer heats up on a sunny day. We aren't having to close the room off from the rest of the house as much now.
A few of the things I learned about spray foam: There are closed-cell and open-cell foams. Closed cell has about twice the R value of open cell. Both seal the structure up better than just about any other insulation. Open-cell is also a good noise barrier, closed cell not so much. Open-cell expands a lot and is very soft and fluffy when it cures, closed cell doesn't expand much at all and is very hard when it dries. Spray foam is kind of expensive. I don't think I could afford to do it to an entire house. It's a very messy operation, everything must be masked off and any over-spray on surfaces that you will want to hang sheetrock on must be scraped off.
Now we are moving along with installing the ceiling in the living area. We're using #1 1x6 pine T&G boards, and it's looking really nice.
There is a lot more labor involved in installing this than I thought, and I'm glad I didn't try to do this myself. The boards are 16' long for one thing, and they are spending a lot of time making sure the joints are nice and tight. I wouldn't have been able to do this by myself.
I haven't decided on a finish yet. If I stain it, it will be a light colored stain. I'm also considering just a clear finish. We'll have a good supply of scrap pieces to experiment with.
After they finish this ceiling, they will hang sheetrock on the ceilings in the garage, then the remaining fiberglass insulation will be installed.
:):)
