Quote:
Originally Posted by fishinpox
Not true
Open cell spray foam @ 3.5" ( 2x4) wall is r-13 . You can achieve r15 with blown fiberglass product called "assure-r" @ 3.5" thick
But
You will get a better seal with the spray foam than you will with the blown fiberglass
Another thing with spray foam is the majority of installers and the majority of Hvac contractors don't know how to properly install / mix product or properly design a Hvac system that works with a sealed envelope
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You are correct on the open cell, I should have specified closed cell. Closed Cell at 1" offers an R14 value, you have to be careful with closed cell if you are doing an attic, you have to calculate your air flow envelop and have proper ventilation. Closed cell will SEAL you roof to a point that it can be a bad thing and cause a mold situation, thus the Air flow envelop calculation, I assumed K was asking about walls.
Quote:
Originally Posted by keakar
I have a decked attic space so I am limited to 6" thick ceiling insulation but I do want the get the best r value there is for it. is there an r21 or something like that?
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guess I should have paid attention better