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-   -   Double Vapour Barrier? (http://www.diychatroom.com/f19/double-vapour-barrier-5910/)

canadaclub 01-14-2007 09:09 AM

Double Vapour Barrier?
 
Hi all,

Going to renovate a basement which has walls insulated half way down by the builder. I am planning to fully insulate to the floor and install a vapour barrier. Question is, can I leave the existing barrier up (which would result in 2 barriers) or will this cause any moisture issues?

Thanks all.

JeepCop 01-14-2007 10:26 AM

Opinions vary GREATLY on this....

I wouldn't do this because I'd be afraid the possible moisture could get trapped in the wall. IMO, it needs a way to escape... but like I said, your mileage may vary...

rjordan392 01-14-2007 11:23 AM

I aggree with jeepcop. The issues between above and below grade walls as to insulation installs are differant. See the following:

http://www.buildingscience.com/resou...stems-2002.pdf

concretemasonry 01-14-2007 12:30 PM

Double Vapour Barrier?
 
What type of insulation do you have in place on the upper portion?

If you are in Canada, you may have to face the concept of the magic line running around the basement at the grade elevation. It does not exist in most other places due to lateral heat flow in conductive materials and the moderating effects of the soil.

Building Science has some intersting concepts. Good luck applying them to an existing real life installation.

If your existing insulation just fiberglass you can slash the paper/poly frequently to eliminate the concept of a vapor barrier.

You will find there are as many concepts as there are thinkers, inventers and conditions. Look to someone in your area that has a basement sucessfully finished for a real life example.

canadaclub 01-14-2007 06:42 PM

ty all for the responses. Yes, it is in Canada where they insulate only to the frost level. I was afraid of a possible moisture lock so I think I will cut the old VB..it makes sense but always appreciate others' opinions.


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