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Insulating a radiant slab

mburgmburg Posts: 36Member
When building a pole barn with radiant heat What is the recommended way to insulate the perimeter of a slab specifically at the locations of garage doors?


  • ZmanZman Posts: 4,812Member
    The edge condition is tricky. If you put it on the outside, you need to find a way to protect it from the weather and insects. On the inside, it forms a crack that some find undesirable. Here is a detail that works pretty well.At the garage door, it has to go on the outside, the 45 degree bevel at the top will help. You could make a metal slip plate at the transition.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mburgmburg Posts: 36Member
    How high up should you go with the insulation at the garage doors? I would imagine you wouldn’t want to go all the way up to the top of concrete floor.
  • hot_rodhot_rod Posts: 11,259Member
    You want to avoid the raw edge of the foam showing. They make a plastic H cap to go over 1/2" foam for isolation between slabs. After the pour you zip the top and put a bead of polyurethane caulk in the space. Not much R-value but some isolation for het transfer and movement.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GroundUpGroundUp Posts: 482Member
    We always put it inside the perimeter, 24" vertical and flush with the top of the concrete. The 2" raw edge will be buried within the wall cavity so it will never be seen, same with the sides of the poles. At the inside of the poles, it gets beveled up to 1/2" on top which again is covered by interior sheathing and acts as a barrier between the concrete and the pole in case of frost shifting. As for the door location, I haven't found anything better than a 45* bevel to a knife edge as of yet unless there is an apron outside. The local lumberyard here sells a 2" thick composite type plank with an R value of 7 that is similar to the material they use for joint control. It's ugly to look at and doesn't stay put unless there is an apron, but it does a good job IMO. Better R-7 at the surface than R-nothing
  • mburgmburg Posts: 36Member
    It appears there isn’t a great option for insulating between interior slab and exterior slab at garage doors. On another note should I tape my insulation joints? I am putting down a vapor barrier under the foam board and taping that. Wasn’t sure if I should tape foam board too?
  • nibsnibs Posts: 212Member
    I tape mine.
  • hot_rodhot_rod Posts: 11,259Member
    SnapCap is the product I used, this company has the expansion joint trims.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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