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Basement Insulation Options

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Posted by: from Markham
1/2/2014 at 9:12:22 AM

I purchased my home brand new 8years ago. I am wanting to finish my basement and use it as a living space. It currently has your typical builder minimum code insulation.

I initially wanted to use 2lb closed cell spray foam but rececently have read some reviews that is making me think twice about it. The other alternative is to use 2" rigid foam (floor to ceiling) as well as insulating the Rim joists and also adding spray foam for sealing minor cracks.(glued or mechanically fastend). I plan on putting in batt insulation (Roxul) to meet/exceed R20, which I understand is the minimum R value in Ontario.

So my question is, do I need to install a vapour barrier/retarder on the warm side prior to putting up drywall? Is there anything in the Ontario building code on this?

Thanks

REPLIES (3)
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Agostino from Drywall Canada Ltd. in Toronto
Date/Time1/2/2014 at 10:25:35 AM

Hi Rocco and Happy New Years!

Section 9.25.4.3 of the Building Code stipulates.

Batt-type insulation should be protected by a vapour barrier.

Products installed to function as the vapor barrier should protect the warm side of wall, ceiling and floor assemblies.

Where different products are used for a vapour barrier and the insulation, the vapour barrier should be installed sufficiently close to the warm side of the insulation to prevent condensation at design conditions.

Hope this helps out.

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Date/Time1/2/2014 at 3:41:59 PM

Yes, you always need a vapour barrier on the warm side, ie. under the drywall.

Do not tuck tape the joints of the ridgid insulation, that will create another vapour barrier and trap moisture between them.

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Date/Time1/4/2014 at 2:53:02 PM

Hi there,

Spray foam is a great option for insulating a basement as it provides great R values, a complete seal and it is self sealing meaning it creates its own moisture barrier. The down side to spray foam is there are some inferior products on the market, and a small percentage of even the good stuff, will not react properly to each other causing a lot more harm then its worth. The other down side to spry foam is it is high commitment and once finished, the space becomes very tough to re-do as you now have to remove all foam in order to access electrical, hvac, plumbing and so forth. Long term commitment required.

That aside, if you would like to use a ridgid foam which is a great product, you can install them floor to ceiling, tuck taping all seams and joints where you will create your moisture barrier and then spray foaming the rim joists to create an air tight seal as well. Then you can install your subfloor, an option like barricade may work well for you here if you wish to create more thermal break on the floor as it has another piece of foam on the underside of the panels providing more r value to the floor. Then frame all your walls on top of the new subfloor, now you can use 2x4 studs instead of 2x6 studs without the ridgid foam and insulate the walls with an r12 or 14 depending on product and surpass the minimum r20 by the obc. If you do not tuck tape the foam on the walls then yes you need to install a moisute barrier over the studs and batt insulation, if you tuck tape the foam then no you do not need to use a 6mm vapour barrier over the walls.

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