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Brick house - brown paper - insulation in walls?

We are renovating our brick home in Minnesota. We took down the lath and plaster on the outside wall, and found that about 3/4 of that wall is lined with some sort of brown paper, behind it is wood, and then the brick that is the outside of the house.

What is the brown paper?


Also, wondering about insulation. We have updated wiring (though there isn't any in this room on the outside wall). Is using rigid foam insulation alright in insulate brick or is it a bad idea?

Re: Brick house - brown paper - insulation in walls?




Most insulation used for residential construction is commonly referred as “batt insulation.” It is made up of two primary components, the fluffy pink stuff and a brown paper like product, which is attached to the fluffy stuff. 


Most of us are familiar with the pink stuff, which is fiberglass insulation, but the brown paper? It’s just something to nail in the insulation.


Actually, it is just as important as the fiberglass because it acts as a vapor barrier, which is very important to controlling moisture in buildings.



The vapor barrier controls moisture by creating a block, or barrier, that the water vapor (moisture) cannot move through. Without getting too technical, there is a constant pressure difference between inside and out of every building. This pressure is what pushes vapor one way or the other, which is why a vapor barrier is needed–to restrict that movement. The vapor barrier is typically placed on the “warm side” of the wall. 



For most structures built 20 years or more ago, installers would tuck the pink stuff between the joists and nail the paper to the bottom of the floor joists, just like they did in the wall studs. 


This is fine for walls because the pink stuff would be facing out towards the cold, but doing the same thing in a crawl space puts the pink side facing up towards the floor where all the warmth is located. This is why the insulation is installed backwards–the pink side needs to be faced down near the colder air. 


Next time you’re in a crawl space, look up and see if the insulation is backwards. If you see silver paper instead of brown, don’t worry–it’s a better quality vapor barrier. But if you see brown paper, you know the insulation is installed backwards, which isn’t insulating any better than plain brown paper.

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