insulating attic wall and vapor barrier
#1
09-25-11, 01:53 PM
insulating attic wall and vapor barrier
My first post on this forum!
We have a one level home in Ontario, Canada. It has stairs to attic area. At top of stairwell, on one side there is a bedroom and other side is a walk in cupboard with a door at back that provides access to attic proper where we store some things and our heat pump airhandler and ducts are located.
The walls that surround the stairwell and the cupboards are 2x4 and insulated with f/g batts. One side is the drywalled conditioned stairwell and other side is the attic. There is no backing on the batts and they tend to fall out.
In summer it gets very hot at the top of the stairs. For this reason and to reduce heat loss in winter, we want to add insulation to the attic side of the studs (and do it in a way that keeps the batts in place!)
Foam board seems the easiest way, but we found that it would need a covering of thin plywood or wallboard. Another option that apparently meets code is to use foil covered insulation. That seemed the easy solution so I have bought some 1" Polyiso with aluminum foil on both sides (this is not an easy area to work in!)
Problem I encountered, was that some of the wall (which was finished piecemeal) has vapor barrier behind wallboard and some areas do not - I think there may be wood paneling behind the wallboard in the areas without barrier.
I have been thinking of ways of retrofitting vapor barrier - vapor barrier paint, sealed in poly sheets, spraying in Great Stuff. But none of them seem too good.
Would you think it would be acceptable to just punch some holes in the polyiso sheathing so that any water vapor that penetrates teh wallboard vapor can escape rather than condense?
We have a one level home in Ontario, Canada. It has stairs to attic area. At top of stairwell, on one side there is a bedroom and other side is a walk in cupboard with a door at back that provides access to attic proper where we store some things and our heat pump airhandler and ducts are located.
The walls that surround the stairwell and the cupboards are 2x4 and insulated with f/g batts. One side is the drywalled conditioned stairwell and other side is the attic. There is no backing on the batts and they tend to fall out.
In summer it gets very hot at the top of the stairs. For this reason and to reduce heat loss in winter, we want to add insulation to the attic side of the studs (and do it in a way that keeps the batts in place!)
Foam board seems the easiest way, but we found that it would need a covering of thin plywood or wallboard. Another option that apparently meets code is to use foil covered insulation. That seemed the easy solution so I have bought some 1" Polyiso with aluminum foil on both sides (this is not an easy area to work in!)
Problem I encountered, was that some of the wall (which was finished piecemeal) has vapor barrier behind wallboard and some areas do not - I think there may be wood paneling behind the wallboard in the areas without barrier.
I have been thinking of ways of retrofitting vapor barrier - vapor barrier paint, sealed in poly sheets, spraying in Great Stuff. But none of them seem too good.
Would you think it would be acceptable to just punch some holes in the polyiso sheathing so that any water vapor that penetrates teh wallboard vapor can escape rather than condense?
#2
10-08-11, 02:46 PM
Member
Not sure punching holes in sheathing is a good idea. Those nasty little water vapor molecules probably aren't smart enough to just head for the holes. I'd be more inclined to treat the living space side where the water vapor is being generated, as in a quality paint designed for that purpose, applied to the drywall.
You might consider improving your attic's ventilation to help with the heat problem at the top of the stairs. Along with increasing the insulation thickness in the stairwell ceiling.
You might consider improving your attic's ventilation to help with the heat problem at the top of the stairs. Along with increasing the insulation thickness in the stairwell ceiling.
#3
10-08-11, 07:27 PM
Thanks for the reply!
I was working on the polyiso installation today. I had a good look at the attic side face of teh wallboard and of the supporting framework. No sign of there ever having been any condensation. Perhaps our existing conditioned side paint acts as a reasonable vapor barrier or perhaps our house does not get too high a humidity.
But, next time we paint, I will make sure we use a paint with low vapor permeability. Benjamin Morre 260 primer seems a possibility.
I was working on the polyiso installation today. I had a good look at the attic side face of teh wallboard and of the supporting framework. No sign of there ever having been any condensation. Perhaps our existing conditioned side paint acts as a reasonable vapor barrier or perhaps our house does not get too high a humidity.
But, next time we paint, I will make sure we use a paint with low vapor permeability. Benjamin Morre 260 primer seems a possibility.
