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Community and Q&A

Insulating Hot Water Lines

artisanfarms | Posted in Energy Efficiency and Durability on

Does it make sense to insulate Pex A hot water runs of 30 – 50′ which will have intermittent use?  For example, a guest bathroom where the shower might be used just a few times a week at the most.  If it makes sense to insulate, is their sufficient benefit to the pre-insulated tubing to justify it’s cost?

My first thought is it doesn’t make sense, but I have missed benefits for a practice in the past, so figured I would ask.

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  1. Expert Member
    BILL WICHERS | | #1

    You're really supposed to insulate all the hot runs. Insulation WILL help, it will help hot water to get hot a little bit faster, and it will help the hot water to ultimately reach a higher temperature at the remote fixture too (both due to reduced heat loss along the length of the run).

    I don't like the preinsulated lines, it's too easy to damage them and things get fussy at hangers and any holes they have to go through. I like the split insulation with the adhesive strip in the split. That stuff installs quick, it's cheap, and it does a good job.

    BTW, insulating cold water lines can help with condensation issues too if you expect high humidity levels.


  2. charlie_sullivan | | #2

    The heat loss from PEX is not significantly different from the heat loss from copper, and it's probably worse than shiny copper (which doesn't lose much heat by radiation). The convection and radiation processes limit the heat loss, not the thermal conductivity of the pipe.

    The insulation is cheap and easy enough that it probably does pay, even for an occasional use scenario, if you are doing the labor yourself and don't mind spending the time. But of course at some point the use is infrequent enough that it's not worth it.

  3. Expert Member


    I don't think I've ever seen insulated hot waterlines. Maybe in a cooling climate it might make sense? My guess is the losses and benefits aren't appreciable enough to bother.

    1. Expert Member
      NICK KEENAN | | #4

      Insulated hot water is code here in DC.

    2. dan_saa | | #5

      There is also the goal of reducing water usage/waste by running water waiting to get hot water. Insulation helps reduce heat loss even with intermittant use such as a kitchen.

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