Weather barrier

rodg2915 · 03-07-2007, 03:47 PM

Our addition is layered (outside/in) Vynil siding, Tyvek, 1/2'' plywood, insulation...Should I then place a plastic weather barrier before the drywall?

concretemasonry · 03-07-2007, 04:38 PM

You should put a poly vapor barrier (6 mil minimum) over the insulation before you hang the drywall.

**AtlanticWBConst.** · 03-07-2007, 07:32 PM

I'm staying away from this one......

concretemasonry · 03-07-2007, 08:11 PM

Atlantic -

Its above grade. I was assuming the home is in a heating climate.

I agree about the many variables effecting the placement and methods for other portions of a home in different climates.

**AtlanticWBConst.** · 03-07-2007, 08:21 PM

Quote:

Originally Posted by concretemasonry

Atlantic -

Its above grade. I was assuming the home is in a heating climate.

I agree about the many variables effecting the placement and methods for other portions of a home in different climates.

Concrete - I completely agree with everything you have noted...

troubleseeker · 03-07-2007, 09:25 PM

I would not put Tyveck and poly ,as you have now created a certain moisture trap in my opinion. As stated, the placement of impermeable barriers such as poly is highly affected by the immediate local climate( often referred to as a micro climate) in your area. Unfortunately these materials are often used in blatently incorrect situations, blocking the ability of the building envelope to properly purge itself of moisture, resulting in hidden rot and mold situations.

**AtlanticWBConst.** · 03-07-2007, 09:41 PM

Quote:

Originally Posted by troubleseeker

I would not put Tyveck and poly ,as you have now created a certain moisture trap in my opinion. As stated, the placement of impermeable barriers such as poly is highly affected by the immediate local climate( often referred to as a micro climate) in your area. Unfortunately these materials are often used in blatently incorrect situations, blocking the ability of the building envelope to properly purge itself of moisture, resulting in hidden rot and mold situations.

FWIW: I agree with NEVER placing a vapor barrier over another vapor barrier. However TYVEK is NOT a vapor barrier...
It is Water resistant, yet vapor permeable.

http://www.tyvek.com/whatistyvek.htm

rodg2915 · 03-09-2007, 01:52 PM

Advice seems to be no barrier thanks just one less item. Appreciate the advice from the pros

troubleseeker · 03-10-2007, 11:28 PM

Quote:

Originally Posted by AtlanticWBConst.

FWIW: I agree with NEVER placing a vapor barrier over another vapor barrier. However TYVEK is NOT a vapor barrier...
It is Water resistant, yet vapor permeable.

http://www.tyvek.com/whatistyvek.htm

I agree that Tyvek is technically vapor permeable, but IMO moisture is going to condense bewteen the inner and outer wall planes. It definately cannot diffuse through the poly, so it's only out is through the Tyvek. However this cannnot happen until the now liquid condensation is vaporized, and can pass through the Tyvek. This process is much slower and leads to a lot of moisture in the wall for a greater length of time. I think the potential for harm is much greater than any positives.

concretemasonry · 03-11-2007, 12:07 AM

troublemaker -

So your absolute recomendation for a heating climate is to not apply a vapor barrier to an inside wall that has Tyvek as a moisture barrier on the exterior? - This seems to fly in the face of all previous recommendations.

It seems insanely foolish to feed the dew point in the wall with moisture from the interior of the home. This adds to the moisture load. I have seen this numerous times in moisture/mold investigations.

Please feel free to offer your opinions to all your customers.