About a grillion of them.
I went with 1 and 2 inch boards. 2 inch first, then 1 inch for a 3 inch total on walls and ceiling. The floor got 2 inches and plywood. I faced the foil out on both sides where there was 3 inches.
The strapping boards were pivotal in aligning and holding in place with HVAC tape.
The envelope was completed with poly plastic sheeting held to the strapping boards with frp rivets, but otherwise allowed to float.
Things I learned:
Great stuff sucks, don't bother except for the occasional gap fill near the wheel wells.
Buy a hot knife, heck buy a few from harbor fright. Just tape the momentary button to on and rest it on something that won't set on fire.
Pave right over holes and cut them out after.
Get the thin mylar tape and the knife will cut thru it. Aluminum HVAC tape sucks for this purpose.
Use your knife to cut radius serrations through the boards to match the curve of the roof the best you can. Try to balance the number of cuts to the least possible.
You can use strips of foam like chinking in a log cabin.
The 2" boards fit between the chair rail inner wall and outer wall, it helps a lot with draft.
Carpet adhesive tape, the pressure kind not the heat kind, from home depot, works fantastic to bond the foam blocks together. Its got peel backing on both sides, and some thin reinforcement thread in the adhesive. Once applied its basically straight adhesive and a couple threads. It will gum up everything you cut it with, eventually. I use a new utility blade and slice it ever so gently and it cuts. Its really great at bonding.
I feel the foam block approach is superior to spray foam but there is more labor. When I picked some walls apart for a test, they were bone dry after rainstorms, snow, condensation, and general abuse of the environment for several months.
I think the slight air gap between the steel skin and the outside facing silvering on the foam is actually desirable, and tends to happen on the arc of the ceiling steel.
Whew long post. Look thru my project to get more foam ideas if you want.
Oh yea the only reason I picked polystyrene vs the fancier higher r rating foam was the cost difference. The higher r value would be nice but because of the way it is installed I think the finished r value is not much different for the same 3 inch thickness.
Originally Posted by MuddaEarth
I'm brain storming on different types of insulation to purchase for Transcendence. I originally was considering spray foam, but upon further research, I decided to go another route. I'm considering using 2" polystyrene rigid foam insulation with an R8 value. For those of you that have insulated this way.....How many sheets did it take to do ceiling, floor and walls? What are your thoughts on this?
Here's a link to what I'm thinking about......