Insulation, Radiant and Vapor Barriers - Insulation - old house
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BHITZ
05-02-02, 04:34 PM
I have an 1850 house that had the old siding removed and 1" rigid insultion boards with metal foil on both sides placed underneath the new cedar siding serval year before I bought it.
I live in Massachusetts and need additional insultation to be able to afford the heat.
One section of the house is losing all of the horse hair plaster so I am planing to insulate from the inside. The rest I'd like to blow in.
Does the foil on the insultion board act a vapor barrier so that I should use unbacked fiberglass to insulate from inside? I'm just worried about trapping moisture in the walls.
Is the blowin insulation going to have enough of a vapor barrier with the foil on the rigid insulation?
I live in Massachusetts and need additional insultation to be able to afford the heat.
One section of the house is losing all of the horse hair plaster so I am planing to insulate from the inside. The rest I'd like to blow in.
Does the foil on the insultion board act a vapor barrier so that I should use unbacked fiberglass to insulate from inside? I'm just worried about trapping moisture in the walls.
Is the blowin insulation going to have enough of a vapor barrier with the foil on the rigid insulation?
resercon
05-11-02, 10:54 PM
The foil that you find on rigid board insulation that goes underneath siding is not a vapor barrier, it is a radiant barrier. It is specifically designed to to allow moisture to go through it in order not to trap moisture in walls. The performance of this foil is determined and measure by what is know as Perm Ratings. Vapor Barrier are determined in the same manner. You can go to http://www.eren.doe.gov/consumerinfo/refbriefs/bd4.html this is a DOE brief on vapor barriers and it discusses Perms.
There is a debate by many organizations concerning Vapor Barriers on How, Why, Where and When to apply Vapor Barriers. Manufacturers of the variety of insulation products make claims. This only fuels the debate. If you read the brief, you'll see that it's written by ASHREA. Though your concerns are warranted, this brief should clear for you on how vapor barriers should be applied and why.
There is a debate by many organizations concerning Vapor Barriers on How, Why, Where and When to apply Vapor Barriers. Manufacturers of the variety of insulation products make claims. This only fuels the debate. If you read the brief, you'll see that it's written by ASHREA. Though your concerns are warranted, this brief should clear for you on how vapor barriers should be applied and why.