plastic vapor barrier w/ batt insulation

[riehlgood]

I am building a new home in the northeast....i.e very hot and humid in summer, very wet in the spring, VERY cold in the winter. My builder/architect is recommending using batt insulation with a plastic vapor barrier inside the walls and tyvek on the outside of the walls. I have heard from a friend that a plastic vapor barrier is a potential serious problem and he is STRONGLY discouraging this choice. Will the choice of a good hvac system help mitigate the problem. Here is a copy of my architects discussion:

"Sorry to disagree but have used a vapor barrier on every project of mine for 25 years and no call backs that I know about. In the winter, there is a huge temp. differential from out to in and all the humidity/moisture is inside. The inevitable condensation forms on the warm side of the wall, with pressure diff. forcing it from in to out. A vapor barrier keeps that moisture from potentially "wetting" the batt insulation because the kraft paper is not enough of a barrier. Wet batt insulation is useless and that last thing you want is water in your wall cavity.

I understand your friend's point on mold and saturation from too much moisture. This is handled with good ventilation, proper humidity and air exchange that keeps surfaces from being over-saturated."

What do people think?

[smokin68]

I can tell you every new home in humid Florida has a vapor barrier, i.e. "house wrap". What is your friend's problem with the barrier, besides not liking it???? It makes for a tighter house. I would think a much greater chance for condensation without it. JMO.

[ambarton]

the idea of house wrap to my understanding is to allow the house to breath without trapping moist air between the walls. unless your builder/architect plans to caulk every and i mean every single penetration of the plastic such as outlet boxes, nail holes and seals all of his seams in addition to laying down plastic on the floor and ceiling joists before they are covered with sheetrock and floor coverings and sealing all of those seams and penetrations, he not only is wasteing his time and effort but your money. this type of vapor barrier will only work if it is air tight. the smallest pinhole WILL allow vapor pressure right through defeating the entire purpose of putting it on in the first place. partially my opinion, mostly facts.

[engineerguy]

http://www.buildingscience.com has the best information on vapor barriers.