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FPSF- insulation under the footings or not. What’s the consensus on here?

Jamie B | Posted in Energy Efficiency and Durability on

Zone 6. Toronto. 

I am getting ready to do a small frost protected shallow slab for a shed. Overkill yes, but I’d like to get one under my belt because I’m a nerd. 

I’m seeing a variety of details on the wild web, where under the “footing”  part of the assembly sometimes does not have insulation spec’d. In my opinion, although its not necessary for heaving protection (like the side wall insulation is), it still would be a cold flanking point in the assembly.  Especially since I’m running radiant heating in the slab. I’m curious/concerned about energy efficiency. 

So, what do people think here. Insulation under the footing or no? 

Jamie

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Replies

  1. Jon R | | #1

    IMO, all FPSFs should use an unheated building FPSF design (which has foam under the whole slab). This will allow you to leave the building unheated, even if that isn't your current plan.

    1. Expert Member
      Malcolm Taylor | | #2

      I agree, and if it's a fairly small shed I'd consider a raft slab, with no thickened footings

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