I recently purchased a slab home with in floor radiant heat. Slow heat up times coupled with fast heat loss & high heating bills make me wonder if the slab was properly insulated. I am considering relying more upon the backup forced air unit to cut costs. My concern is that all of my plumbing runs through the slab. How low can I drop the in floor heat without risk of freezing my water pipes? Could I ever rely upon only the forced air for heating - does that warm the slab enough to prevent frozen pipes - I'm guessing not? Also, I live in Minnesota where January highs are sometimes below 0.

Your frost line may be as deep as 50" but noit under your slab. If the sab is heated even by the back up system the concrete is not going to reach freezing. If homes in your area have had problems you can add a glychol antifreeze to the water in your boiler.

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Originally Posted by harwaaah

I recently purchased a slab home with in floor radiant heat. Slow heat up times coupled with fast heat loss & high heating bills make me wonder if the slab was properly insulated. I am considering relying more upon the backup forced air unit to cut costs. My concern is that all of my plumbing runs through the slab. How low can I drop the in floor heat without risk of freezing my water pipes? Could I ever rely upon only the forced air for heating - does that warm the slab enough to prevent frozen pipes - I'm guessing not? Also, I live in Minnesota where January highs are sometimes below 0.

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A quick follow up question to clarify...


So, just the warm ambient air that is produced by the forced air vents located on the ceiling will sufficiently warm the slab enough to prevent freezing household water pipes?

Thanks!

Right, picture this. 20 below outside will touch the ground and slowly lower the temp, the soil freezes and goes deeper but around 50" down the warmth of the earth keeps the soil temp above freezing. Now for the house, 70 degree air in the home keeps the surface of the concrete at about 60, as you go deeper you are reaching toward that warm earth under the home, it never freezes, the houyse acts like a big isulated blanket on the slab. The only things to caution is near the foundation edges there could be a little frost under the slab because it is so close to the exposed soil around the outside of the home.