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Insulation options for room above garage - polyiso the best?

Insulation options for room above garage - polyiso the best?

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  #1  
Old 08-15-12, 07:57 PM
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Question Insulation options for room above garage - polyiso the best?

Hi,

I have a room above the garage which I struggle to keep under temperature control its either too hot in the summer or too cold in the winter.

One solution I am thinking off is attaching polyiso to the ceiling of the garage with drywall over the top.

Is this the most effective option?

I will also be adding more loose cellulose insulation in the attic surrounding the bonus room.

Thanks.
 
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  #2  
Old 08-15-12, 08:21 PM
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What is above this room? What are the walls like?
 
  #3  
Old 08-16-12, 06:32 AM
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Just an attic above the room. I'm having loose cellulose added there to take it up to 12inches.
 
  #4  
Old 08-17-12, 11:49 AM
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Just an attic above the room. I'm having loose cellulose added there to take it up to 12inches.
You said that earlier, didn't you. Oops... But still, what are you doing with the walls?
 
  #5  
Old 08-17-12, 11:55 AM
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Sorry!

I am not doing much with the walls (the house is 11 years old) so assumption is the insulation within the walls is adequate - or am I wrong? On one wall that borders with attic space I will be having polyiso attached to the attic side.
 
  #6  
Old 08-17-12, 02:31 PM
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Not to take from Nashkat on the walls answer, is there any insulation in the ceiling of the garage? You could foam board below the joists after installing cavity insulation, just no vinyl flooring above. This would decouple the room from the airspace below, after air-sealing the top plate holes (wiring, etc.); BSI-009: New Light In Crawlspaces — Building Science Information Foil-tape the seams. Notice the insulation gap to floor above only after the foam board.

Use 5/8" drywall per fire code, ADA it: Info-401: Air Barriers
Plug the garage door ceiling brackets holes, electrical boxes for openers, and fire-tape the drywall for air-tightness of your new air barrier.

Gary
 
  #7  
Old 08-17-12, 02:36 PM
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Unfortunately I don't know what insulation is in the garage ceiling. It is finished on both sides. When you say "foam board" is that different to polyiso?

The flooring in the room above the garage is carpet and will remain so.
 
  #8  
Old 08-17-12, 07:33 PM
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Same, though the facing can change. They used foil-faced in that link. XPS would also work. Underground is a different story; https://docs.google.com/viewer?a=v&q...4EyM707m0gPdXQ

Gary
 
  #9  
Old 08-17-12, 08:46 PM
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I am not doing much with the walls (the house is 11 years old) so assumption is the insulation within the walls is adequate - or am I wrong?
IDK. While the
too hot in the summer and too cold in the winter
issues point most intuitively to a need for better insulation above and below the room, heat gain or loss through an exterior wall can also be affecting this room more than others. Was this room finished out as part of the original construction?

Gary has given you some solid advice on what you might do below, and your plan to add blown-in cellulose above may do what you need there. Twelve inches of cellulose should give you R-45.6, just for that material alone. That seems a bit much. You can use the ZIP-Code Insulation Program to learn the optimal value for your house. I plugged in some basic assumptions for a house in a ZIP Code beginning with 010, and got R-38 for the attic.

Is the attic well ventilated?
 
  #10  
Old 09-18-12, 11:05 AM
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