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-   -   Vapor Barrier (http://www.diychatroom.com/f103/vapor-barrier-154136/)

daveyboy 08-18-2012 09:20 PM

Vapor Barrier
 
I have an older home 50 yrs approx. It is insulated and 1 inch plaster. Can I just build a wall on top of the other wall insulate vapor barrier then drywall. Not sure what I should be doing regarding vapor barrier

joecaption 08-18-2012 09:26 PM

Why would you want to build another wall, if it's already insulated and plastered?

That would be a whole lot of work for little gain unless you built that wall out enough to add R-13, then you would have to build out every window and door jamb.

daveyboy 08-18-2012 09:32 PM

There is very little insulation in the walls. Instead of tearing down the outside walls I just want to build a 2x4 wall on the inside insulate then vapor barrier.

I am changing all of the windows anyways.

I just don't want the mess of tearing down the plaster walls.

I am sure adding R-14 with another wall will help surely can't be bad.

I am just not sure if I need to add another vapor barrier or will it now cause condensation on the old or new insulation.

joecaption 08-18-2012 09:54 PM

You would be way ahead and far better off just getting rid of the plaster and old lath, air sealing, adding fire blocking if it's old ballon wall constrution, redoing any old wiring, shimming out the studs, adding insulation, vaper barrier, then sheetrock.

Your would not loose as much space in the room, no chance of a double vaper barrier condition that can cause a ton of issues, not as hard to deal with the window and doorway issues.

Going to have to trust me on this one, it's what we did for the last 15 years on many older homes. It's not as bad as your making it to be.

Gary in WA 08-19-2012 01:09 AM

"I am just not sure if I need to add another vapor barrier or will it now cause condensation on the old or new insulation." -------

It depends on your location for the correct Class of vapor barrier/retarder. Where is the house?
Describe the existing wall materials...

Gary

daveyboy 08-20-2012 10:50 AM

Here is how it was:

Brick, wood planks, insulation with paper backing towards the inside, plaster.

Now it is:

Brick, wood planks, insulation with paper backing towards the inside, plaster, R-14 insulation, 6mm poly, .....

What I need to know is should I leave the poly on or remove it or put holes at the bottom and top between every joist so it can breathe and then put the vapor barrier back on. I have already studded the new wall, insulated it and vapor barrier. I just want to make sure I have no condensation issues.

I live in Niagara Falls, Canada, near buffalo, NY

Thanks

Dave

Gary in WA 08-23-2012 01:34 AM

Your local AHJ may require a poly vapor barrier on the inside. The paper-faced vapor retarder is hygroscopic, variable perms; http://www.buildingscience.com/docum...vapor-barriers If the bricks have the air-space to the wood boards, moisture can exit there. I'll let you decide on the code required poly for your location: http://www.google.com/url?sa=t&rct=j...3dQqtw&cad=rja

Gary


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