Underslab insulation

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swayampadhi
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Underslab insulation

Post by swayampadhi » Tue Jan 22, 2019 1:03 am

Hi

I have purchased a pre construction semi detached home in Brampton, ontario.
The basement is unfinished.
My builder is providing a strayfoam underslab insulation as an upgrade for $3000.
Just want to know if it is beneficial for maintaining the heat and cold in the basement

Considered the price and my basement is unfinished if its worthwhile to do it now.
Secondly while finishing my basement at a later stage, are there ways available i can insulate my basement floors and walls

Thanks
Swayam

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Shannon
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Re: Underslab insulation

Post by Shannon » Tue Jan 22, 2019 8:21 am

These are all good questions. I am not fully sure about this . I am used to slabs on grade (garage floors) with hydronic heating being insulated . I usually see rigid foam used ,likely because of the cost of sprayfoam? Slabs on grade are different because they are right on the cold surface that is frozen in winter where as when you start to sink the basement floor into the ground the deeper you go the closer to a consistent temp year round you get if you are below the frost line. Rigid foam will not be sealed as well because it has T&G seams where as the spray foam is sealed completely. Also rigid foam may give you some waste from cutting to fit.I would say rigid foam is cheaper to purchase but will take a little more labour to cut ,fit and install.

Now the real question is it worth it under a basement slab? That is something i'm not completely sure about .Some new energy codes in certain areas may require that the slab is insulated and in that case you have no choice other then which product to use SF or rigid. If your area does not require it by code and you are using carpet for flooring then I don't think it is worth it IMO if you are using hard surface flooring like LVP then I could see a definite benefit .

Can it be done in different ways later on? ...yes . Are they better? ...not likely. In the over all scheme of things I guess it is up to you but I guess I look at it this way. You are spending hundreds of thousands of dollars for a new home, this cost of $3000 is likely less then 1% extra in cost to the total of the project so i think it could be worth it just in comfort alone. I know there are always lots of extras when building a home and you have to pick and chose. IMO when it comes to energy efficiency these are important factors for your entire future living there . Even though most of those are not as evident and rewarding as spending $3000 dollars on a new TV they are likely more important I would say.
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Aaron
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Re: Underslab insulation

Post by Aaron » Tue Jan 22, 2019 10:41 pm

My dad has underslab insulation done for the basement of the lake home he built 3 years ago in northwestern Wisconsin. I think he just use like 2" thick foam board under the poured concrete. I'm guessing maybe the re-bar had to stake it down so it wouldn't float but I didn't see it done.

My dad is an insulation freak, and he spared no expense in that regard. The whole house is spray foamed and pretty air and vapor tight.

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Shannon
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Re: Underslab insulation

Post by Shannon » Wed Jan 23, 2019 9:14 pm

When I built my garage 15 some odd years ago I used cut outs from exterior doors. We had a door company here and they where giving them away. So I got a whole bunch and laid them on the compacted gravel installed my rebar and then tied my infloor heat pipes to the bars. Not sure how effective it really is but it was cheap. Lol
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Aaron
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Re: Underslab insulation

Post by Aaron » Fri Jan 25, 2019 11:06 am

Insulated exterior door cutouts? The cutouts that are done for the windows? Wow. Nice way to "upcycle" that waste. In-floor heat is a great idea, I am surprised my dad didn't go with that for the basement of the lake house. I think he figured the insulation was good enough. He heats and cools the lower level with a split system; the ductless thing. On the first level he has ducts but it apparently still uses the same split system. It's like a different zone or something.

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