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Greg_R 11-14-2012 07:04 PM

Insulation retrofit
 
My house has an addition that is connected to the old part of the house by a long staircase. The backside of the stair is exposed to an uninsulated garage (covered by drywall but no insulation). We can feel cold air rolling off these stairs. The stair is maybe 20 linear feet and the drywall panel (easily accessible portion) in the garage is maybe 6'-8' long. I want to cut this section out, insulate up into each cavity, add vapor barrier if missing, and patch the drywall.

Questions:
1) I'm assuming I'll want vapor barrier (6 mil plastic) against the stairs, followed by insulation. Since this is a dry area, an external sheet of Tyvek is not needed. Sound reasonable?
2) Should I consider a spray insulation kit or just fiberglass batts? Would foil-backed foam boards be ideal here?
3) I have a suspicion that one entire side of the cavity will not have a vapor barrier (it's an internal wall). In that case I may need to extend the vapor barrier along that side and tie into the barrier between the garage and house (let's hope that part exists!). Would that change my decision on #2?

I'm going to punch a hole in the drywall tonight to see what I'm dealing with.

Windows on Wash 11-14-2012 07:46 PM

Quote:

Originally Posted by Greg_R (Post 1052271)
My house has an addition that is connected to the old part of the house by a long staircase. The backside of the stair is exposed to an uninsulated garage (covered by drywall but no insulation). We can feel cold air rolling off these stairs. The stair is maybe 20 linear feet and the drywall panel (easily accessible portion) in the garage is maybe 6'-8' long. I want to cut this section out, insulate up into each cavity, add vapor barrier if missing, and patch the drywall.

Questions:
1) I'm assuming I'll want vapor barrier (6 mil plastic) against the stairs, followed by insulation. Since this is a dry area, an external sheet of Tyvek is not needed. Sound reasonable?
2) Should I consider a spray insulation kit or just fiberglass batts? Would foil-backed foam boards be ideal here?
3) I have a suspicion that one entire side of the cavity will not have a vapor barrier (it's an internal wall). In that case I may need to extend the vapor barrier along that side and tie into the barrier between the garage and house (let's hope that part exists!). Would that change my decision on #2?

I'm going to punch a hole in the drywall tonight to see what I'm dealing with.

Where is the home located? All of the vapor barrier recommendations are climate/location specific.

Be sure you do not combine vapor barrier and create an inescapable trap.

Greg_R 11-15-2012 12:35 AM

Home is in Portland, or. Thanks!

Windows on Wash 11-15-2012 06:22 AM

http://energycode.pnl.gov/EnergyCodeReqs/?state=Oregon

http://www.google.com/url?sa=t&rct=j...R3sGGVFLlfyahQ

Greg_R 11-15-2012 12:09 PM

I'm seeing the following:

Quote:

No assembly constructed in Climate Zone 4, 5, 6 or 7 requires a Class I vapor retarder (i.e. a polyethylene vapor barrier). The approach does not prevent you from using one, it just does not make you use one.
It sounds like I can just shove insulation into the cavity and call it good. HOWEVER, I am concerned about the air flow from/around the stairs (can "flag" a piece of toilet paper).

Windows on Wash 11-16-2012 08:59 AM

Seal all the gaps with foam prior to insulating and you should be fine.


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