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Room Addition -- Opinion on insulating between wall/ceiling at overhang

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  #1  
Old 11-07-11, 01:14 PM
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Room Addition -- Opinion on insulating between wall/ceiling at overhang

Hello,

I'm needing some advice on how best to insulate where my ceiling meets my walls on two sides for a room addition. My ceiling is made out of 2x10's at 16in OC as I'm using the attic for storage.

I assume I should use baffles on the edges where the roof meets the wall/ceiling so the air can flow thru the soffitt vents?

My main question is ... what is the best way to ensure when installing bats of fiberglass insulation that go up and against these baffles that as little air can get thru as possible? Should I put up a vapor barrier prior to putting up my ceiling?

Here are the areas I'm talking about ... where the walls meet the ceiling and the most air could come in...



Thanks for any help!
Brian
 
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  #2  
Old 11-07-11, 01:58 PM
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Hi woodcycl,
I assume the storage area is not going to be heated, thus you need to air seal 100% between your new room and that upper space. They air tight electrical boxes and IC AT cans for recessed. I don't see a lot of overhang for soffit vents. Your effective vent area needs to be 1 sq ft for every 300 sq ft of attic floor. That assumes very good air sealing and a vapor barrier. Split that half high and half low.

Those look like 2x4 walls so you will not get as much insulation as I would suggest. Think mineral wool as it eliminates air flow. Seal all of those electrical penetrations with a fire fated caulk or fire rated foam.

Your double top plate will be a cold spot and there is minimal room for insulation over the top of it.

As for the area in question, I would install the baffles up to the floor above and fill that space, again, with mineral wool as opposed to fiberglass. Then a continuous vapor barrier across the ceiling and then the drywall.

Bud
 
  #3  
Old 11-07-11, 02:22 PM
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Bud,

Thank you for the information and suggestions. I did a quick search online and don't see many, if any, local options for me to pick up mineral wool insulation unfortunately. There is one place, in Louisville, KY area, that came up. So, I'll try calling them tomorrow. Otherwise, I'll go w/ the standard fiberglass even though I see that it isn't as efficient. Cost is also a concern in my situation since we had a builder go awol and we are in court trying to get back the $$ he took. uggh.

Thanks,
Brian
 
  #4  
Old 11-07-11, 03:32 PM
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Just noticed the Roxul brand of wool insulation at Lowes!
 
  #5  
Old 11-08-11, 06:33 AM
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Location: New England
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I was just going to say, I see Roxul all over the place. I have been using a bit of it and it sure will stop the air flow. Use a long serrated knife and you can detail any cuts you need.

As far as awol contractors, if you are required to give them money up front, find a different one or agree to give the money to a lawyer, why does that sound just as bad?

Bud
 
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