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should i replace wool insulation above porch with spray foam?

should i replace wool insulation above porch with spray foam?


  #1  
Old 07-04-14, 06:47 PM
O
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should i replace wool insulation above porch with spray foam?

Hi All,

I wondered if someone might share some wisdom. I'm getting some insulation done and i thought they should also tackle the ceiling of the porch which my master bedroom overhangs. I'd initially thought there wasn't much insulation up there when i poked my eye through the light socket. However, after removing some of the panelling it seems theres between 2-3 or even 4" of wool insulation (not rockwool; house is old).

From this link wool apparently has R9 per 2.36 inch or R3.8 / inch, spray foam has around R6/inch and i think that might be on the high side.

So if i had 3" wool, R11.4, i'd need at least 2" of spray foam to even equate the wool. I'm not sure what would be a common thickness to put under a porch.

Then on top of all that there's the removal cost of the old materials and most likely there would be a cost to replace the porch ceiling.

Would other people go to the trouble or would they just leave it? I guess it's personal but i'm starting to think it's not worth it.

thanks again
oman
 
  #2  
Old 07-05-14, 04:22 AM
B
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Join Date: Oct 2008
Location: New England
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Are you having heating/comfort issues in the bedroom above? In addition to insulation, air sealing is very important. Foam accomplishes both, but drywall is also a good air barrier if all penetrations are sealed, like that light box you mentioned.

As for R-value, R-6o would be a minimum in my opinion. Code minimum is probably R-49, but floors are often hard to keep warm with a cold space below.

Bud
 
  #3  
Old 07-05-14, 05:31 PM
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Thanks Bud,

The cold isn't an issue in the room above, mainly because the radiator is too big / isn't balanced in that room. There is air leakage between the bricks though, coming out through cracks in the plaster. But i think that is from holes in the motor which i've noticed around the outside.

thanks for the advice

oman
 
  #4  
Old 07-06-14, 03:52 AM
B
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Bricks will often have a gap behind them to help with drying. Just mentioning that so you don't seal up a hole that was put there intentionally. Brick can be fussy.

Bud
 
  #5  
Old 07-06-14, 01:55 PM
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How big are the floor joists? I would probably just fill the rest with dense pack cellulose. R-25 is the recommendation for a floor. These recommendations are really for new construction. You do the best you can when retrofitting older homes. Air sealing can have a huge impact on your energy efficiency.
 
 

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