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Old 01-02-2020, 09:24 PM   #16
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Re: Basement insulation for the Enbridge Home Efficiency Rebate


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Originally Posted by user_12345a View Post
New homes in ontario come with full height R20 basement insulation.

That being said...

1. Spray foam has great properties for basements, but is flammable and toxic. Foam must be covered by something non-flammable.

I would only spray foam the rim joist area as it's near impossible to get that part well sealed with a barrier.

2. Vapor barrier with batts against the wall doesn't perform well in basements. The barrier traps the moisture in the wall assembly, reducing r-value and increasing risk of rot.

Vapor barriers only work well above grade due to drying potential to the outside.

If you have wall framing all around, remove the existing batt insulation.

Put 2" of rigid foam or roxul board directly on the wall to provide a thermal break. The thermal break stops thermal bridging to the studs and also stops condensation from forming.

Rigid foam has a higher r-value than roxul board. Both are unaffected by moisture.

Put roxul batt insulation between the studs, and only if required by the auditor/codes, put a vapor barrier on loosely.

The barrier is not needed when there's a thermal break.

Your gross r-value will be R-24 with foam and a bit lower with roxul board.

Insulate the rim joist area with rigid or spray foam. Cover that insulation with cut roxul batt to comply with codes re: exposed foam.
My wall is 2x4, so it will be R-12, not R-20, right?
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Old 01-03-2020, 07:13 PM   #17
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Re: Basement insulation for the Enbridge Home Efficiency Rebate


The pictures show a gap between the framing and the foundation's wall.

If you can, get rigid insulation behind the framing and put batts between the studs to get the r-value up, create a thermal break to stop condensation and reduce thermal bridging.

It may be hard to slide insulation behind the framing.

Roxul 2x4 insulation R-14.

Combined that with R8 to R10 of rigid insulation and get R-22 to R-24 gross and outstanding thermal performance.
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Old 01-03-2020, 07:22 PM   #18
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Re: Basement insulation for the Enbridge Home Efficiency Rebate


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99% of the houses I have built have basement with some most all below grade, they are all built with a plan for living space in the basement.

I live in one without a problem

I have only seen a few done with out fiberglass insulation.
BC climate is different than ontario's. With the exception of the coast, BC is dry.

If a house is well built from scratch, it will have better than normal water/damp proofing, so moisture coming from the foundation won't be as much as a problem.

30+ year old subdivision mass produced homes in ontario can have a lot of moisture coming into the basement from the foundation. The older the house, the worse it is.

You can insulate in a way that is less than ideal and not have major issues, but the r-value is still diminished.

Fiberglass plus vapor barrier simply sucks for basements. You don't get anywhere near the stated r-value once moisture gets in the wall assembly.

You can have a thermal break with sufficient r-value to stop any condensation and use fiberglass or roxul batt without a vapor barrier.

I think building science courses should be mandatory for general contractors/carpenters/code enforcers/hvac guys to maintain certification - the way things are now people justify poor practices simply because they worked before and never learn.
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Old 01-03-2020, 07:42 PM   #19
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Re: Basement insulation for the Enbridge Home Efficiency Rebate


Quote:
Originally Posted by user_12345a View Post
The pictures show a gap between the framing and the foundation's wall.

If you can, get rigid insulation behind the framing and put batts between the studs to get the r-value up, create a thermal break to stop condensation and reduce thermal bridging.

It may be hard to slide insulation behind the framing.

Roxul 2x4 insulation R-14.

Combined that with R8 to R10 of rigid insulation and get R-22 to R-24 gross and outstanding thermal performance.
Would you mind suggesting a Youtube video to do this?
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Old 01-03-2020, 10:25 PM   #20
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Re: Basement insulation for the Enbridge Home Efficiency Rebate


Won't be any videos of sliding rigid insulation under framing. You have to assess what you have and see if it's practical.

It won't be easy - may need to remove studs and reinstall, particularly if you use foam.

The gap between the frame and foundation may not even be large enough to provide a good thermal break.


Roxul board gets fastened:

The video shows installing a vapour barrier to comply with code. See my previous comments about that.

Foam gets glued with special adhesive.
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Last edited by user_12345a; 01-03-2020 at 10:27 PM.
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