We are remodeling our basement and have two exterior walls that we need to insulate. We have 500 square feet of exterior wall space with 1/3 of it above grade. I was quoted $1000 for 2 inches of closed cell spray foam including the Rim joists, taping off and cleanup. I figured I can do these same two walls with two inch thick, closed cell rigid polysterene board. and some cans of great stuff for the rim joists for about $550. Are the benefits of spray foam or the payback enough to justify another $450? The only real advantage I can see is the the better sealing but if I do my job cutting, tyvek taping the foam board and applying the great stuff. I think I can seal it up pretty good too. What are your thoughts?
That doesn't sound too bad to me, the spray-in stuff is what pro's use these days and is definitely better than rigid board with you sealing the seams. They will get it done in half the time it takes you, if that. you should really be looking at R-values. Polystyrene is approx 4 R-value per inch. Polyurethane is upwards of 8 R-value per inch. I'm assuming your quote was for polyurethane spray. If this is the case, then it is a no-brainer. Spend 40% more to have something done in 50% of the time that is 100% better.
How? I've used both quite extensively and I don't see the obvious benefit in spray foam. I have never seen any manufacturer will claim an R8. Most that I've dealt with our between six and seven. Also regular Styrofoam is an R5 per inch, if you get the foil faced, that is an R6. Honestly if you can save yourself a couple hundred dollars doing it yourself, I would go for it. I would use the foil face in the rim joist though. It as a vapor barrier on each side in an area where is highly vulnerable to moisture. Sent from my iPhone using Tapatalk
If it takes any length of time to do it yourself, I can't see it paying for that little saving. I would avoid the hassle have it done.
We just built a garage/shop. Here the going rate is $1/inch of thickness per square foot. I had them do 1" of foam on the whole thing and then layer batts over the top. I asked the owner of the company what his opinion was and he said in his own place he did the same thing. There is no doubt that the commercial spray foam does a better job than the foam board. My vote have them do it, or have them blow 1" and then do batts over the top to save some cash and increase the R-value.
If it were me, I'd have them spray it. I hate working with foam. Not having to clean-up after it would be worth the extra $$ for me, not to mention my time getting, cutting & installing.
The foam spray is the way to go because it seals and provides insulation while the foam board just provides the insulation. I used the foam spray when installing a window in my cabin and it was clearly better than other spots where I didn't use something that expands. On the gap between the door I packed regular insulation between the jam and it was still letting some air in whereas the foam between the gap on the window let nothing in at all.
Is 2" enough for your climate zone? The only issue I have with spray foam is the quality of the job depends on the installer. How they mix, and more importantly how evenly they spray. As long as they spray a true uniform thickness of 2" (or whatever you plan to put on), that would be fine. As long as you take precautions to air seal with the foam board (tape the joints, adhesive backing applied to the wall, spray foam the base and joints up by the rim joist), it will be just as effective. A lot more work, though I'm with Fitz, in my situation (and I'm all about DIY), I would probably pay the extra for the convenience.
Personally this is one area where I feel the Minnesota State building code needs to be updated. The code says that a foundation wall and rim joists only needs an R10. This is fine if these are below grade, but personally I feel if it's above grade it should be at least what the typical wall insulation needs to be, which is a R19. Sent from my iPhone using Tapatalk
I'm getting one more bid this weekend. After recalculating all my costs with foam board (foam board, spray foam, tape, caulk) I'm at a $300 difference. To me that's worth it for the spray, although I hate waiting on a contractor for my project. I'll check on adding another inch on the portion above grade.
The obvious benefit is not having to close in any seams and the product having an inherantly higher R-value. And it would take easily half the amount of time to spray in vs adhering boards and sealing seams. I don't know about manufacturers, I'm just going off of generic info on insulation types. Foam and Foam Board Insulation | DoItYourself.com Apparently you are confident both polystyrene and polyurethane have exactly the same physical characteristics. I'm confident they don't. Structural Insulated Panels from Iowa Coolers
I'll preface this by saying that I am actually a big fan of polyurethane closed cell spray foam. I try to convince all of our customers to spend the money on it, it's a great product that to me is worth the cost. The only reason I would say to go with the Styrofoam is that it would've saved a few hundred bucks because you install it yourself. Now to address some of your comments. Yes, spray foam has higher R value per inch but to attain the desired R10, it would be cheaper to go styrofoam. Yes you are right on the time, it would take a lot less time to install the spray foam, but if you are installing the Styrofoam yourself why would this be a factor? You are not paying yourself. As far as me being confident that both polyurethane and Styrofoam having the same characteristics, that's not what I said. I said the benefits you receive is similar. There are two things you look for in a building envelope, insulation value and adequate vapor barrier. Both of these can be achieved in either Styrofoam or polyurethane spray foam. The other argument is that the spray foam will seal it much tighter. this is not true if the procedure the OP mentioned is used. Personally I'd like to leave about a half an inch between foamboard's and then use spray foam to seal them tight. Again I'll say that my preference is purely for the benefit of saving a few hundred dollars. Spray foam would be cleaner and quicker. Sent from my iPhone using Tapatalk
Sorry the OP asked what would be better, not what would be cheaper. Sure you can acheive the same results, but since we now know that R-value differs, you will need more than 2 inches of polystyrene to acieve the same results as 2" of polyurethane spray foam. If the OP is considering installing 2" of either product, then obviously the spray foam will provide a higher R-value. Is that better? If your goal is to insulate your home, then polyurethane is better. If your goal is to insulate at the lowest cost, then its a different answer.
