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Is Tyvek necessary?

fairwinds's Avatar
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06-09-04, 08:42 AM   #1  
Is Tyvek necessary?

Hi. I'm building a new 2 story house in PA, which will be about 2900 sq ft. The contractor uses a styrofoam insulation board in areas that are not structural and underneath a little stone work in the front. Plywood will be used everywhere else. I am concerned that the builder will be placing the vinyl siding up against the wood. Do I need to have the builder place Tyvek over the wood and styrofoam? The builder says no, I'm not sure. The price will be in the neighborhood of $1000.

As you can probably tell, this is the first house I've ever built and I am a novice at all of this. Please offer any advice you may have.

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resercon's Avatar

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06-09-04, 06:21 PM   #2  
Yes, for two reasons.

The first is for wind driven rain. Neither the foam board or building felt are as effective as Tyvek when dealing with wind driven rain.

The second is air infiltration. Neither the foam board or building felt are effective air barriers. Tyvec, besides being a more effective water barrier than either the foam board or building felt, it is specifically designed as an air barrier. This by itself warrants its application and probably pays for itself in energy savings.

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07-07-04, 12:54 PM   #3  
not an absolute must, but it defintely has it's advantages. especially if you're keeping this house for a lengthy period of time.

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07-13-04, 02:40 PM   #4  
Tyvek not required

Under Pennsylvania building code nothing is required under the siding and Tyvek is NOT superior to rigid foam is protecting from wind blown rain.

In fact Tyvek is very poor as a weather barrier against liquid water when applied over OSB and plywood.

The adhesives in the plywood and OSB break down the surface tension of water which is really what prevents water from penetrating Tyvek.

Tyvek becomes a sieve to water when installed over most plys and OSB sheathings.

Rigid foam insulation is superior in every way.

But the long and short is that Tyvek nor any other secondary weather barrier is required in Pennsylvania.

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