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laundry room – inside/outside thermal envelope?

mikhailwatt | Posted in General Questions on

Good day all,

I’m getting to the point of running new hvac ducting for what has turned into a complete interior revamp/reconfiguration…

Currently the laundry room (plus storage/pantry closet) is within the conditioned space, with a door to the garage – rough sketch attached. The plan was for dryer exhaust, room exhaust fan and a/c supply.

Now I’m re-thinking combustion air and issues with drawing conditioned air from the living space, etc.

(Hot/humid Central Texas, not super-tight construction)

Comments/suggestions welcome!

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  1. severaltypesofnerd | | #1

    You thinking of adding a tight door to the laundry, and leaving it out of the conditioned space? Seems fine.

    Consider getting a blower door test and working on air leaks first, before sizing your systems.

    1. mikhailwatt | | #4

      Might be overthinking - how "conditioned" does the "pantry" want to be?
      Perhaps a tight door on the pantry as well. Or switch to an electric dryer, problem solved.

  2. Expert Member
    DCcontrarian | | #2

    The only thing I would worry about is freezing weather. It will wreck you washer.

    1. mikhailwatt | | #5

      Ha - the plumbing manifold in the (unfinished) utility room froze up in the Big One a couple winters ago - that room will be insulated plus a just-in-case electric heater.

      1. Expert Member
        BILL WICHERS | | #6

        Try to keep all your plumbing on interior walls, and if you have to run plumbing on exterior walls, make sure the plumbing is on the INTERIOR side of the insulation. Don't run the plumbing "inside" the insulation, since the insulation then acts to keep the plumbing colder, by insulating it from the interior of the room.

        It might be worth putting heat tapes on the water supply lines if you've had freeze issues in the past.


        1. mikhailwatt | | #7

          Right - the supply comes in on an interior wall, but the exterior wall in that room wasn't insulated yet. No cracked pipes, but an O-ring let loose on the manifold, so it was a harried trip to Lowe's for shark-bites and pipe insulation to rig a bypass. We got off easy, a lot of people here weren't as fortunate.

          1. Expert Member
            BILL WICHERS | | #11

            If you want to build in some extra insurance, put in some shutoff valves with bleed ports on the inside of the main structure where the branch lines for the laundry rooms start. If you expect some unusually cold weather, or the power fails during cold weather, you can shut those valves and use the bleed ports to drain off enough of the water in the branch runs to prevent freeze issues. For this to work, you want to slightly pitch those branch lines back to the valves with the bleed ports to aid with draining.


          2. Expert Member
            DCcontrarian | | #13

            Bill --

            You also have to get the water out of the washing machine itself, particularly the valves and pumps. The way I do it is to blow compressed air into the water inlets while starting a warm water cycle. Then pour about a quart of plumbing antifreeze into the washer drum and run a spin cycle.

  3. Andrew_C | | #3

    Assuming the shaded areas are currently outside the air barrier, I'd leave things where they are and just get an electric dryer instead of gas. And replace the gas HW heater with electric or HPWH when the time comes.
    I can't think of what you'd store in an unconditioned pantry in Texas, other than rocks.

    1. severaltypesofnerd | | #8

      How does the electric dryer improve things? In Texas are external air sourced dryers a thing, to avoid heating air conditioned air?

      1. mikhailwatt | | #9

        No combustion air required.

        No idea if it's a Texas thing.
        Just had the question - in reality, how inefficient/uncomfortable would it be to have the dryer drawing make-up air from the living space vs. an outside source.

        The house originally had the laundry inside, with gas & vent for a dryer hookup and a small HVAC supply register in the ceiling - can't remember if it had an exhaust fan. But it's an older spec home and -every- expense was spared.

        1. severaltypesofnerd | | #10

          No combustion air, but it's still pumping air from inside (through the clothes) to the outside.

  4. jwasilko | | #12

    Would you consider a heat pump drier? No need to worry about venting or the dryer pushing conditioned air outside....

  5. Expert Member
    MALCOLM TAYLOR | | #14


    Before going ahead, check what your building code has to say about the idea. Ours precludes both plumbing, and any appliances that connect to it, being located in unconditioned spaces.

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