i am always looking for a good deal on things, especially nowadays. A local yard is selling 4x8 sheets of the pink extruded polystyrene for $4 per sheet, R 7.5. I am trying to decide if this is a good enough deal to leap at to get stuff for my (as yet) uninsulated house, I would want to cut it and put it in the stud bays (doubled up) and then possibly for crawspaces, or ?
What do you think? Jump or let is pass?
mt
Sounds like a deal to me but how would it compare to per square inch for fiberglass? Achieving a good tight ft in stud bays with rigid foam is pretty time consuming and air leakage is actually a greater heat loss source for most homes. But the price sounds really good and for crawlspaces it could be a very good choice.
Mike,
Another good place to insulate with the foam board, if you have a second floor or a wood framed first floor and crawl space, is the rim joist between the studs. Use caulk or spray foam insulation to seal around the edges.
Tom
Having fitted rigid foam sheet into a couple stud bays I totally second the comment about it being difficult to fit to close clearances. A tight fit is necessary, there's no point in going to all the trouble without it being a tight fit.
I believe you would be time and money ahead if you used the sheet foam on the exterior.
How about squirting in some GreatStuff expanding foam along the hard to seal edges of the foamboard. If it doesn't eat the foamboard it should seal it well.
Great Stuff works, itis compatible with the pink foam I used. It's also messy, not cheap and more bother than I would want. I used the pink foam in some header areas. I would not want to do the entire cabins worth of walls with it. That's just my opinion though.
I agree about the great stuff----excess expansion is hard to avoid and even harder to remove.
thanks, folks.
I decided to be more casual about the rigid stuff. I will not put it in my walls, but if there is enough available next time I am there, I will get enough for some crawl spaces, etc.
mt
I would jump all over that deal. I plan to use rigid foam for my primary insulation in full 4x8 sheets, so that would be a great money saver for me.
You might consider using that pink board on the outside of your studs. It is a solid enough base to nail through to support your sheathing or siding.
If I had come across the material earlier in the project, I might have jumped and put it on the exterior. But I already have started my siding, so I am trying to figure if this is useful for interior applications. I am thinking of using it as a crawl space and underneath the floor joists between the main floor and by basement.
mt
I used those 4x8 extruded sheets on interior walls of my little cabin. I agree with the tight fit BETWEEN the studs, but I nailed them directly on top of the studs, butting the edges tight together right in the middle of each stud. Since the line was there, I knew right where to nail on the t&g carsiding, 16" o/c. I did the front and back gables the same way.....jb