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spry foam vs. rigid foam and mineral wool

dings's Avatar

Join Date: Oct 2009
Posts: 69

04-19-10, 05:51 PM   #1  
spry foam vs. rigid foam and mineral wool

probably about 2 months away from putting insulation in the old house I gutted. I was going to use spray foam (which I can have installed at dealer cost), but the rest of the budget is taking a hit. I am planning on redoing all the siding soon so I was thinking about putting ridged foam on the outside of the house and Rolux inside. how tight will I be able to get the house doing it this way vs the spray foam? I would hate to save a little money now and waste it later on heating costs.

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Speedwrench's Avatar

Join Date: Apr 2008
Posts: 1,698

04-19-10, 06:33 PM   #2  
it all depends on how stringent you are on filling all of the spots air leaks can occur in, I used ridgid foam on the walls of my house with a vapor barrier outside of that and filled every crack and hole with spray foam from a can in 1995 and it made a huge difference in my heat and air bills the the tune of over $75.00 a month at the time. Needless to say since then I have saved way more than the cost labor and materials, the house was other wise insullated with fiberglass batts, (horrible insullation)

Murphy was an optimist

hironomous's Avatar

Join Date: Jul 2009
Posts: 54

04-21-10, 09:02 PM   #3  
You will certainly get better insulation and air sealing with the spray foam, but given the level of insulation you can acheive with rigid at R5-R6 per inch and Rockwool at R4 per inch, I suspect it would be more than adequate if you seal reasonably well with caulk and/or canned foam. In a cold climate, I don't think you want a vapour barrier on the outside.Maybe Tyvek or another air barrier,but with foam,I don't think you even need that.

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