Insulation with or without Airbarrier
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| Posted in Energy, Heating & Insulation on
When insulating a basement ( North East ) how do you determine if an airbarrier is neccesary or not on an interior below grade application– when researching some people are using a airbarrier ( tyvek) against the cememt block wall then the insulation folllowed by the vapor barrier and finally drywall. Since not everyone follows this method. When is it neccessary to add the air barrier ?
I also notice no one ever mentions waterproofing the cement block from the inside ? Is this a waste of money ? I have not experieinced any water damage however the house is 50 years old and who knows when or if anything will start ?
Replies
Although I'm a big fan of air barriers above grade in northern climates, I don't see the point in using one below grade against a reasonably sound masonry wall.
Re a waterproofing treatment, interior treatments are rarely very effective.
Well, that Tyvek ought to do a gfood job of keeping all the wind from coming in through that concrete wall underground! I always worry about too much worm exhaust getting into my living spaces.
;)
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Plastic.......definately! Tyvek? I don't think I've ever even heard of that. Ridgid foam betweem nailers is a must as well.
You need to maybe get up to date. Never heard of Tyvek ... like saying you've never heard of kleenex. NOT plastic!! ... he's talking about on the exterior surface of his furred out wall. You are referring to a vapor retarder (AKA barrier), I think (the plastic). The Tyvek is an air barrier ... like Gortex for houses ... let's vapor through but not bulk moisture and it is for the exterior surface of the wall ... they usually put it on after the sheathing (i.e. under the siding).
I think the point he was making was that he has never heard of Tyvek used on basements walls.... and not that he has never heard of Tyvek the product.
For the OP, I am in Northern Ontario and have never seen anyone put Tyvek on a basement wall here ... interior or exterior.
At times I see people add rigid foam on the outside of basement walls, while interior basement walls are for the most part all done using regular fiberglass insulation, with a vapour barrier on the warm side.
Dealing with a leaky basement by waterproofing the interior wall seems like a very poor way of dealing with a problem that originates with water coming in from the exterior.
I've had the Spray Foam quoted - R13 is twice the price of Rigid + Roxul (R14) and R24 closed cell is almost double again -- so how important is the R factor when dealing with below grade applications ?
I'm thinking the R13 Spray foam is the way to go so I get the benifits in the headers of the closed cell without spending more than neccessary to get all the way to R24.
Lose the Tyvek for this application ... it does nothing for you. Waste of money. Install foam plastic insulation (e.g. XPS polystyrene or wnat one of the other posters mentioned).
here's little reading
http://www.buildingscience.com/search?SearchableText=basement
can you spray-foam your walls? Closed-cell foam takes care of air and vapour barriers. Or, instead or tyvek, use 1" foam against block wall, then batts in framing. Just keep water vapour away from dew-point surfaces, but don't let it get trapped in behind (especially basement) drywall. We used to always leave bottom 12 inches of walls in basements uninsulated to keep footings and drain-tiles from freezing, and v-b inner side of framing to floor, but i see more recommendations for semi-permiable(sp?) wall finishes.
We used to always leave bottom 12 inches of walls in basements uninsulated to keep footings and drain-tiles from freezing,
If you're possibly freezing the footings and walls in a basement,...you have bigger problems to solve than finishing a basement
In general, I agree, but this could bea function of his topography and soils and climate variations.There were places in CO, where the official frost depth was 4-6 feet, but once in twenty years, it might freeze to ten feet deep in places.
The presence of ledge nearby can make a difference too. I note that he is in Quebec. I don't know how far north he is, but the local climate may be part of ths.
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Thank you for all the insight -- Actually I'm in Southern Ontario rather than Quebec and I'm getting pricing on the closed cell foam option but at first glance its at least 3 times the price of rigid + batt insulation.
It is worth twice as much , but there is still that initial sticker shock to get over
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when in Canada .. check out NRCs site .. waterproofing on the inside is only done remedially, the pref is to do it outside, as for tyvex, not arround here, not sure if you thought the tyvex would be against the conc inside or outside, iether way it's not necessary. If you do use batts (roxul is better than fiberglass), just make sure it's not touching the concrete, spray foam is still stupidly expensive. We are required to insulate 4 ft below the grade, anymore and your loosing out on free heat in the winter ..
Ontario Boy