Wall vapor barrier

[1969grad]

I am building a new house. The first floor has a brick veneer and the second floor has a wood panel type exterior.

My question regards the vapor barrier. On the first floor the insulation contractor installed a insulation without a backing and a visqueen (spelling?) vapor barrier. On the second floor he installed the insulation with a paper backing type vapor barrier.

The reason he gives for not installing a visqueen vapor barrier on the second floor is that the insulation might sweat and get wet.

Does not sound correct to me. What is the opinion of this forum? Should there be a visqueen vapor barier on the second floor also?

 

[kenvlach]

VisQueen® is a brand name for polyethylene film that's been used so long it's often used generically, without capitalization.

You certainly need a vapor barrier for the 2nd floor [building inspector would notice if missing], but it doesn't have to be PE film. The advantage of using PE is that it comes in large widths & hence is also good at stopping cold air infiltration at any gaps due to insulation settling or installation of conduit or plumbing.

Not sure exactly what 'paper backing type vapor barrier' you have on the 2nd floor. I presume you are using roll-type fiberglass insulation between wood studs. The aluminum foil backing is perhaps best, but plastic-coated paper is also OK. For both, make sure the the stapled flanges are overlapping, flat & tight to the studs – you can add extra staples.

“The reason he gives for not installing a visqueen vapor barrier on the second floor is that the insulation might sweat and get wet.” -- This is nonsense, the moisture comes from within the house. However, probably not a good idea to add visqueen over an existing vapor barrier as moisture could get trapped between the two. For additional vapor barrier protection, e.g., for bathrooms or kitchens, some aluminum paints are very good & keep moisture out of drywall or plaster altogether.

 

[1969grad]

You are correct that the insulation is fiberglass between wood studs. On the second floor, it most likely is a plastic coated paper and is labeled as a vapor barrier. The insulation is stapled to the inside of the studs.

He used this type of insulation also in the wall between the living room/laundry room and garage for the same reason I guess.

The point is why did he not use a visqueen type vapor barrier on the second floor instead of the plastic paper.

At this point all that could be done is to install the viqueen over the plastic paper vapor on the second floor. Do I need to insist that he add the visqueen?

Like I said it does not seem consistant.

 

[kenvlach]

As long as the 2nd floor insulation is installed right, you needn't worry. It's probably the most standard method of home construction for the past 50 years.

I'm thinking that there should be a layer of tarpaper between the brickwork & the sheathing. Thus, it's more important to have a tight vapor barrier for the 1st floor walls, as it is much more difficult for any moisture to egress.

 

[1969grad]

Thanks kenvlach.

Since I am in my late 50s this will be our retirement home and with the soaring energy prices the objective is to get a energy efficient home.

My background has more to do with pipe insulation and metal building insulation where noise is the primary concern so I feel like I am sorta out my area on this one.

 

[haneyrm]

1969grad, Is your new home located in a humid climate. In Florida, vapor barriers are installed on the "hot" side of the wall section to prevent moisture from getting to the insulation. On most homes with wood construction, a product such as a Tyvek house wrap is applied to the exterior of the building before any siding or stucco is installed. As I understand it, in northern climates, the reverse is true. typically visqueen is the last thing that is installed over the insulation before drywall is installed. If the Kraft paper from your insulation is facing the interior of the home, it sounds like it is installed correctly in a northern climate. In Florida, the possibility of having moisture problems and degraded insulation are severe if the vapor barrier is installed on the "cold" side of the wall. Enjoy your new home. I just recently completed construction of a new home and the experience is worth the price of admission.

 

[kenvlach]

haneyrm,
If you build a wood home in Florida, don't worry about the moisture -- the termites will consume it!!!
You make a good point. The air conditioning causes a dehumidifier effect, with the walls as condensers.

Last time I was in Florida, seemed like mostly poured & block concrete homes.

 

[1969grad]

All:

Thanks for the help. BTW, I live in OK where it normally gets cold enought in the winter to kill all the bugs. However this winter we have had only a few weeks of cold weather so there may be a price to pay next summer.

 

[haneyrm]

Kenvlach,

You hit the nail on the head with the termite comment. The number of homes damaged around here each year due to termite infestation is staggering. Most homes are block/stucco. Even though the exterior does not represent a good meal, these critters always seem to find their way into the interior walls and have an absolute feast. I can tell you first hand, getting rid of termites is an expensive proposition and your insurance company wants no part of it.

Mike

 

[amorrison]

Contact your electric and/or gas utility - they should have customer service engineers that will give you the correct advice for your area/climate.

 

[pennpoint]

1969grad
Too late for you I'm sure but I am seeing more and more Tyvek wraping of outer framing prior to veneer applications.
These are pictures I have seen in the Southwest and West so take it for what its worth where you are.
My thoughts are seal the walls and ventilate the space within.

pennpoint



Best regards
pennpoint

 

[cme]

Vapor barriers for humid climates go on the outside of the building: IE paint w/ low vapor permeability

For northern climates they go on the room side of the insulation

 

[walkes]

I have been noticing that a lot of housing construction in northern climates have the vapour barrier on the room side as well as the Tyvek air barrier on the outside.