Vapor barrier?

[dr_swami]

Hi

I'm renovating the basement of an old house in Victoria, BC. The climate here is typical Northwest. It rains a lot, but rarely does it get below freezing.

The building code in this area says I should put vapor barrier on the external walls between the drywall and the insulation. This is to prevent in-house moisture from penetrating through the drwall and insulation and condensing against the cold external walls. It's the same building code across Canada.

My carpenter says however, that this code is relevant in climates like Alberta where it gets to -10 and stays there for months on end, but that for climates like BC where it hardly ever gets below freezing it does more harm than good. His recommendation is that I not use vapor barrier on the external walls and simply drywall right over the insualtion. According to him, in temperate humid climates like British Columbia, vapor barrier seals the moisture in the walls and causes more wood rot and mold than without it.

(He does, however, recommend putting vapor barrier up against the foundation (~ 2 feet) BEFORE the insulation and then drywalling. That, he says, is to prevent the outside ground water moisture from coming in through porous concrete and into the walls.)

What is your guys' opinion? Is he correct? Would you vapor barrier the external walls between the insulation and drwall in humid climates that rarely get below freezing?

Thanks for your thoughts.

Jack

[Noozer]

Vapour barrier should be placed on the warm side of the wall. Anyplace in Canada that would be the side towards the living space. It's to prevent the humid air in the living space from getting through the wall and condensing in your insulation and framing.

If you want to put any kind of barrier on the cold side of the wall, use something like Tyvec... It allows air movement through it but is designed to reduce moisture movement through it.

[Joseph Meehan]

Go with the code.

[marson]

i am personally skeptical about the advisability of fiberglass insulation in a basement. fiberglass and moisture is not a good combination. in a basement, you not only have to worry about moisture from the house, you also have to worry about moisture from the concrete walls.

IMHO rigid insulation is the way to go in a basement. there are a number of options for attaching drywall. USG makes a z strip that fastens to the wall and provides a surface to screw drywall to.

BTW you could go with a vapor impermeable primer on your drywall, instead of plastic.

[HotRod]

I live in Ontario and ahve to say that vapour barrier is really easy to put up. Make sure that they also put some around all of the light and electrical boxes to stop air movement. IT's hardly worth debating. BUT like another post I'd use rigid foam if the basement has ever had water in it or urathane spray foam.

[Goedjn]

I'd use a spray-on close-celled foam as both insulation and vapor barrier. You get no condensation against the sheathing because there's no way for air to carry water there, and you get no condensation against the vapor barrier, because the "exposed" surface isn't cold.

[Mac Cool]

No. Go with the vapor barrier and ditto on the rigid insulation. You don't want mold.

[dr_swami]

Thanks for everyone's response. It seems like the consensus is that I should use vapor barrier. However, I haven't received any good arguments for other than the reason I mentioned.

My carpenter specializes in renovating old homes. He says that he's never taken apart a house that did not have vapor barrier and had problems with mold, but he's taken apart many homes WITH vapor barrier and seen lots of mold and wood rot.

I'm not sure who to believe.

Jack

[marson]

your carpenter has a point about never seeing mold in houses without a vapor barrier. i hink old houses are so leaky that they are vented naturally. but if this is a basement with concrete walls, it might be a different story. my house is 90 years old--probably without a vapor barrier, but someone tried to finish part of the basement some years ago and now it's a rotted mess. it was water from the outside, i'm pretty sure. so i'd ask him how many old basements insulated with fiberglass he has dealt with.

[dr_swami]

So I asked a vapour barrier expert. His main job is to repair water damaged homes. And he confirmed what my carpenter said. Best not to use vapour barrier if you're building outside of code.

His rationale was that IF there ever is water damage, the vapour barrier will hide it and prevent it from being noticeable on the drywall. In the meantime the moisture will do a lot of damage to the walls and end up costing a lot more to repair than had you noticed the water damage on the drywall and gotten to it right away.

You learn something new. I've decided NOT to vapour my house in the temperate climate of Victoria, BC. In colder climates, definitely use vapour barrier.

Cheers, Jack

[Mac Cool]

:

The insulation will minimize the heat differential between the concrete walls and the conditioned air space inside helping to prevent condensation on the walls. The vapor barrier will keep the moisture inside further preventing condensation on the concrete wall. Ever walk outside in the morning and see dew or frost on your car windshield? The windshield is a vapor barrier keeping the condensation outside, rather than inside.

If you are having moisture problems from outside then do not use fiberglass insulation, use rigid foam.

[Glen]

Jack,

Do as you will - Vapour barrier or no Vapour barrieer. However, I'd recommend talking to a local building association for advice prior to making you final decision.

I happen to live just a couple hours north of you. Nanaimo.

Before making your final decision on this matter check out the Vancouver Island Home Builders Association and maybe call the local building inspectors. You can call anonymously if you like and ask your questions (contrary to popular belief, the inspectors are there to protect the homeowner!). The Home Builders Association can probably supply you with some free information as to the whys and wherefores of vapour barrier and the inspectors would prefer to have the questions asked before it creates an issue - so that you don't have the costs of repairing it after if it is done incorrectly.

Just my 2 cents....

Best of Luck on you project!