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I am converting about 900 sq.ft. of attic space to habitable and I have to insulate. What would be the best and most economical solution?

by LiveModern Webmaster last modified Aug 20, 2013 01:12 AM
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by last modified Aug 19, 2013

The roof has typical vent holes on the sides, but when I sheet-rock the habitable area, about half of the roof will not have ventilation. From what I gathered so far, closed cell spray foam is rather expensive. At about $1/bd.ft., to achieve R30 I need about 4.5". The house has about 2,500 sq.ft. footprint, probably about 4,000 sq.ft. of roof area, so I am looking at a whooping $18,000. Way to expensive. The roof is made out of 2x6 joists, but I furred the habitable area with 2x2's. I can think of several ways to cut down the bill. One would be to spray 1" closed cell, then fill up the rest with open cell. Another would be to use batt insulation on the ventilated areas. I live next to San Jose, CA. Weather is quite dry, it rains only a few months in the winter and even when it rains it's still dry. What would be the best and most economical solution?




 

 

The roof has typical vent holes on the sides, but when I sheet-rock the habitable area, about half of the roof will not have ventilation. From what I gathered so far, closed cell spray foam is rather expensive. At about $1/bd.ft., to achieve R30 I need about 4.5". The house has about 2,500 sq.ft. footprint, probably about 4,000 sq.ft. of roof area, so I am looking at a whooping $18,000. Way to expensive. The roof is made out of 2x6 joists, but I furred the habitable area with 2x2's. I can think of several ways to cut down the bill. One would be to spray 1" closed cell, then fill up the rest with open cell. Another would be to use batt insulation on the ventilated areas. I live next to San Jose, CA. Weather is quite dry, it rains only a few months in the winter and even when it rains it's still dry. What would be the best and most economical solution?

Yes, you are correct that closed cell spray foam can be expensive, but the $18,000 you quoted is out of this world, especially for converting 900 square feet of attic...


 

 

 
 
 

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