Insulation half the walls? why


Old 01-12-10, 02:13 PM
Thread Starter
Join Date: Jan 2010
Location: Canada
Posts: 2
Insulation half the walls? why

Hey guys!

I bought an house 6 months ago here in Canada and notice this while doing some renovation:

The basement is almost completed and drywall sheets as been already installed.
There is 2 inch extruded Polystyrene sheets for Insulation between the footing and the drywall but... I'd like to know why it is not fully insulated?

I mean there is an empty space, like 2 feets from the floor where there is no extruded Polystyrene sheets?!?! Basement is like 5 feets deep and there is only insulation on 3 feet out of the 5 wich leaves 2 feets with no insulation.

Is this for the humidity? ventilation? what is the purpose or the theory behind that?

Should I remove the drywall and put some insulation? we are in the middle of winter here and I don't feel it to cold...

Thanks for your input!
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Old 01-12-10, 02:54 PM
Join Date: Oct 2008
Location: New England
Posts: 9,995
Hi Eth and welcome to the forum. There are two reasons to do as they did. One, the majority of the heat loss in a basement is from the exposed concrete down to one foot below grade. Plus of course the rim joist above the foundation. The second reason is to allow a little heat to escape, thus holding off the frost a little and protecting the foundation from being cracked.

heat that is lost to the basement floor and below grade walls has to travel some distance before the northern winds can blow it away. Slowing the loss of heat is exactly what insulation does, so the earth outside acts as a big insulator. The closer to the surface, the more important the insulation becomes. If you want a project, next summer when the ground is a bit softer, bury rigid insulation one foot below grade, sloping out 4' to a depth of 3'. Helps to drain water away from the foundation and protects the foundation against frost and heat loss.

Being in Canada, the 2" is good as long as they sealed the foundation to the rim joist and all wood seals around the perimeter of the walls. As with all well sealed homes, be sure they took steps to provide combustion air for your heating system.

You are all set,
Old 01-12-10, 03:54 PM
Thread Starter
Join Date: Jan 2010
Location: Canada
Posts: 2
Thanks for the input Bud!
Old 01-13-10, 11:59 AM
Join Date: Aug 2009
Location: NY
Posts: 326
Should be fine. Probably the bare concrete isn't that cold, is it?

FWIW, Ontario building code that takes effect soon or recently did take effect calls for full height basement insulation with a maximum of 15" uncovered at the bottom.

There is unfortunately no quantifiable recommendation on when a person should or shouldn't go full height based on various different factors, so to date most people going with partial height have done it to either save money or somewhat intangibly protect against frosting issues. Still, in your case there's no reason in the world to rip out the drywall and put in more foam. You'll save negligible amounts on heating and won't have that anti-frost benefit, even if it isn't always meaningful.

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