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Community and Q&A

Insulating copper pipes for a heat pump that run in an exterior wall.

marcjb | Posted in General Questions on

Hi gang. I’ve been installing mini-split heat pumps lately, all as retrofits until now. My latest install is in a new build and I’ve had to run the insulated copper pipes inside an exterior wall. My concern is condensation on these pipes when the unit is used for cooling. My plan is to insulate the back of the cavity with 1.5″ xps, seal the edges and all penetrations into the cavity with spray foam, and then finish insulating with batt. They’re using poly for an air barrier behind the wall finish. What do you think? Should I put xps on the sides of the cavity as well? Many thanks for your thoughts.

Also, this is in BC’s mild marine climate.

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  1. Expert Member
    Dana Dorsett | | #1

    The service temp of XPS is about 160-165F (~72C) , and I'm not sure where the peak temp of the refrigerant lines are (do you?).

    The service temp of spray polyurethane or rigid polyiso is something like 220-225F (over 100C), and is probably the better choice. As long as the peak temps of the refrigerant lines never exceed 100C in either heating or cooling mode you can probably just spray the lines with 3-4cm of FrothPak (1.5lb density polyurethane, available in small kits at box stores), and use rock wool for the cavity fill.

  2. marcjb | | #2

    Fujitsu tells me the peak temp is 150F. Also, the copper pipes are wrapped in Armaflex foam insulation that prevents condensation, so there I go. No worries and thanks for your input.

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