# Detached garage foundation insulation worth it or no?



## veeps (Sep 7, 2017)

My detached garage foundation frost walls were just poured. I’m in Connecticut and plan to only heat the garage intermittently when I go out there to use the workshop. My inspector says rigid foam on the foundation walls is a waste of money. What are your thoughts? I plan to at the least damp proof it.


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## stick\shift (Mar 23, 2015)

Above or below the slab?


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## veeps (Sep 7, 2017)

stick\shift said:


> Above or below the slab?


I’m referring to the foundation walls below the slab.


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## Nealtw (Jun 22, 2017)

intermittently and between those times both sides of the insulation will be cold. It would take weeks if ever for heat to get to what would be the warm side.


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## u2slow (Feb 9, 2012)

I had mine damp proofed because one end is 30" below grade. Vapour barrier under slab. No foam. It doesn't get brutally cold in the PNW, but lots of wet. I'm not heating my shop yet, but the concrete seems to take on ground temperature more than it swings with outdoor ambient.

Of course... if doing in-slab hydronic heat, you'd want to insulate.


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## veeps (Sep 7, 2017)

u2slow said:


> I had mine damp proofed because one end is 30" below grade. Vapour barrier under slab. No foam. It doesn't get brutally cold in the PNW, but lots of wet. I'm not heating my shop yet, but the concrete seems to take on ground temperature more than it swings with outdoor ambient.
> 
> Of course... if doing in-slab hydronic heat, you'd want to insulate.


Well my footers are 42” below grade. Now I’m debating if it is worth damp proofing it or not.


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## Nealtw (Jun 22, 2017)

veeps said:


> Well my footers are 42” below grade. Now I’m debating if it is worth damp proofing it or not.


The only reason to insulate would be that deep frost that might transmit inside. You would be protecting the heat that is n the dirt as mentioned by @*u2slow.* It is usually in the mid fifties like your incoming cold water.


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## Old Thomas (Nov 28, 2019)

I am in western NY and I have 2 continuously heated outbuildings. One is 36x48 and the other is 40x60. Neither has insulation below grade or under the slab. I built one in 1993 and the other was built in 1999. No problems yet. With continuous heat it might be better with an insulated perimeter but the heat bill are modest and I don’t care. With occasional heat, you will never drive the heat into the ground so it will have a minimal benefit.


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## veeps (Sep 7, 2017)

Thanks for the info.


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