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Cold bathroom

user-6623302 | Posted in General Questions on

I have been trying to figure out why my large bathroom is always several degrees cooler that the connected bedroom. I suspect it is due to a lack of adequate return air flow.

The space is heated with a high velocity air system. The 3 outlets are located along one wall, half way between the cold shower area and the doorway to the bedroom. The return air duct is located in the hall outside the bedroom. The only door is never closed. I am thinking it is like a thumb on the end of a straw. No air moves from that back area. Your thoughts?

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  1. user-2310254 | | #1


    You may be focusing on the right issue. But my questions may be helpful in trying to troubleshoot this issue.

    What type of flooring in the bedroom and the bath? What is the temperature setting for your HVAC system? Are the two rooms sitting on the same type of foundation?

  2. user-6623302 | | #2

    The cold end is tlle on cement board and the warmer area is hard wood. All over the same foundation, an uninsulated cellar. The thermostat is in the bedroom next to the door leading to the hall. It is set at 68 degrees. The puzzling thing is that the cold are is always within 2-3 degrees of the bedroom.

  3. Jon_R | | #3

    The vents on the outlets need to direct air towards the cool area. With sufficient face velocity to cause good throw and mixing.

    How are you measuring temperature?

  4. user-6623302 | | #4

    I have two thermometers which read almost the same when I switch their locations.

  5. user-2310254 | | #5

    I imagine that the tile is playing a role since it is a better conductor than the wood flooring. The temperature in my home is pretty uniform in each zone, but the tile in my bathroom certainly feels colder than the adjoining wood floors. Have you considered installing electric radiant under the tile or adding some other type of heater?

  6. Jon_R | | #6

    When it comes to bare feet, tile will feel colder, even at the same temperature. But a thermometer isn't fooled by this.

    I think your temperature problem is fixable, but for even more comfort, it might be worth it to seal/insulate the cellar and slightly over-heat it.

    Don't worry about return airflow through an open door (although total return flow from bath+bedroom could be an issue).

  7. user-6623302 | | #7

    The problem is an air temperature issue. I am trying to avoid adding more heat but will if I have to. Going to try moving a supply outlet to blow into the cold end and see if that helps. I am looking for the least expensive solution. If that doesn't work, I may try some other kind of forced circulation. Last resort is a radian panel or a fan coil of some sort.

  8. Jon_R | | #8

    I'd focus more on the vents direction and velocity (vs location). You can experiment with proper mixing by using a portable fan blowing towards the cold end.

  9. user-723121 | | #9

    Why not insulate the cellar?

  10. Expert Member
    Dana Dorsett | | #10

    What Doug said. Air sealing the band joist & foundation sill is a high priority, followed by insulating the basement walls. The room could easily be cold due air leaks into the space under the floor, air sealing and insulating would fix localized cool spots in the floor, and lower the overall load by raising the floor temp a few degrees.

    If the door is almost never closed, always open, the path to the return is as low-impedance as it can possibly be- there's no thumb on the straw with the door open, but with the door closed it could be an issue.

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