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Community and Q&A

Insulating chilled water pipes.

rhl_ | Posted in General Questions on

When installing an air source water heater/chiller one needs to worry about insulating all the pipes to prevent condensation. If one installs a pipe through a piece of wood, does the insulation need to go through the wood as well?

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  1. this_page_left_blank | | #1

    To prevent condensation, all you would need to do is seal the penetration on both sides. No connection to the ambient air means no moisture source, and the modest heat transfer due to the missing insulation will be averaged out with the adjacent pipe sections.

  2. Expert Member
    Peter Yost | | #2

    Hi Ryan -

    First, right on Trevor!

    While I have never seen air sealing around pipe insulation, that would get you extra building science points. The main way condensation is avoided is by the insulation everywhere but the wood, the wood is not a horrible conductor, and both the moving fluid and conductivity of the pipe averages it all out.


  3. Expert Member
    BILL WICHERS | | #3

    I work with large chilled water plants commercially all the time. I spec continuous insulation on all the chilled water lines, both supply and return. Any wall penetrations that need to be sealed are usually either made tight to the insulation and sealed with mastic or “duct seal” (it has to be a little flexible). If you don’t need a fire rated penetration seal, you can use a rubber sheet with holes cut a little smaller than the diameter over the insulation to make a gasket.

    For hot water lines, I would run the pipe through the wood, seal the pipe to the wood with caulk, then insulate up to the wood on both sides. Don’t worry about running the insulation through the wood.

    The reason for the difference is that cold water lines sweat, hot water lines don’t. I’ve seen any exposed part of cold water lines sweat, and then the condensation wicks into the pipe insulation and causes problems. The chilled water line can chill the material it’s passing through enough to cause condensation on that material sometimes.


  4. Expert Member
    Akos | | #4


    Chilled lines need to be fully insulated and air sealed otherwise they will sweat and cause issues (common to see ceiling damage in commercial places where a someone took the insulation off a valve to adjust it).

    This is the big challenge with chilled setup for house cooling, if you are not meticulous with your insulation, they will cause problems. You can get pre-insulated PEX lines for use with outdoor stoves, about the only way I would run chilled lines inside the house. This means big holes through studs to fish the line with insulation and all.

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