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Styrofoam Under Thermostat ?

My thermostat is mounted on an inside wall that has no insulation.  The wall tends to be cold both from an adjacent room that has air infiltration leaks and from the basement which is unheated (except for the heat from the boiler burners).

I have packed as much polyester wool into the hole in the wall where the thermostat wires come through as I can, but I still think the thermostat is picking up some cold from the wall itself.

I am thinking of putting a block of styrofoam under the thermostat to insulate it from the cold wall. Here are my questions:

1. Is styrofoam the right material to use ? In a fire does styrofoam give off cyanide gas or is that just an urban legend ? Should there be a foil backing ?

2. How thick a block of styrofoam should I use ? 0.25 inch, 0.5 inch, thicker ?

3. Should the styrofoam just cover the area behind the thermostat or should it extend a little beyond the thermostat perimeter to shield cold from the edges of the stat also?

4. Where is a good place to find small styrofoam sheets ? A craft store ?



  • EricAune
    EricAune Member Posts: 432
    Heat goes to cold, period.

    The stat is likely doing its job, heat goes to cold and the only way to change that is to tighten up the adjacent room. 

    You could change the location of the stat but the energy spent conditioning the space will always want to migrate to the colder room causing added run time.
    "If you don't like change, your going to like irrelevance even less"
  • SteamHeat
    SteamHeat Member Posts: 159
    edited January 2010
    Can't Fix The Air Infiltration Right Now.

    I have a family member in hospital and the air infiltation problems will require a lot of time hunting them down. It is more than just the window frame. There is no insulation in the walls and the cold air is coming from both an exterior wall and from the basement. I agree that the cold air is cooling off the room, but the wall is cooling down first and faster and tripping the stat prematurely. Thus my desire for a quick band-aid fix of an insulative material under the stat. When more time is available to do it right, I think I'll need an infrared thermometer or a good probe thermometer to hunt down all the leaks, open seams, hidden holes, etc.

    I was thinking of the Extech 445815 as a probe thermometer since it also reads humidity and dew point and that might help me in the basement and in the summer with a/c regulation. Does anyone have a recommendation for a good IR thermometer.
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