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Community and Q&A

Insulation for below-grade polyethylene pipe?

lance_p | Posted in Mechanicals on

CZ6A, Ottawa ON

When installing a ground loop for a heat pump, what is typically used to insulate the PE pipe where it travels under the slab and footings?  I don’t want the loop freezing any soil below the house, and I don’t want heat transfer between the incoming and outgoing pipes.

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  1. GBA Editor
    Martin Holladay | | #1

    Are you an installer of ground-source heat pumps? If not, trust your contractor.

    If your ground loop is properly designed, the fluid in the loop (which is often ordinary water, but is sometimes water plus glycol) shouldn't freeze. That said, I've heard of situations where the ground loop experiences very low temperatures at the end of winter.

    You can buy pipe insulation rated for burial if you want. That type of pipe insulation is often used for installations of outdoor wood-fired boilers.

    1. lance_p | | #2

      Martin, I am the potential installer of a future heat pump system. We are building on a lot with plenty of space for a horizontal loop, and the lot will have plenty of fill, up to five feet at the foundation. Installing a ground loop makes sense now as it likely wouldn't be possible in the future, or would at least not be practical.

      The house will initially be built with a gas furnace, but I'd like the option to go to a GSHP in the future. Having the ground loop already in place and slightly oversized is the plan. We'll need about two tons of heat, so a 3-4 ton ground loop is the goal, between 1500-2000 ft of pipe. In our climate we'd likely end up using a mix of water and glycol.

      Long story short, I don't have a contractor lined up to install a heat pump but I'm planning to install the ground loop. I'll check into the boiler line insulation as you suggested. Thanks!

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