We live in the central USA, where temps are often below freezing for several months a time. We have an attached garage which is insulated, so usually stays above freezing due to heat coming through the house walls, as well as off of cars as they cool down after being driven. This causes a lot of the snow and ice debris to melt in the garage. We do have floor drains which drain away the liquid moisture, but due to all of the melting snow/ice, the garage is often very humid, causing condensation on the garage door, exterior windows of the garage, as well as on the cold cars themselves at times.

We really enjoy the above-freezing garage temps to gradually melt the snow/ice, but don't like the high relative humidity in the garage. Does anyone have suggestions on what could be done to help reduce the humidity in the garage without a lot of cost or equipment? Putting a source of heat to raise the normal temp in there isn't really an option. I could put a residential dehumidifier in there, but I'm concerned that since the coils operate near to freezing temps already (which is what causes the water to condense on them and drain away), that the below 40 degree garage air will just cause them to freeze up with the condensed water before it can drain away.

  • I don't know if a dehumidifier would help much. By the time the humidity rises to the point where the dehumidifier would condense moisture, all the other cold surfaces would also be condensing moisture. A vent might help, can test it by cracking a window open. It would also lower the temp a little delaying the snow melt and evaporation.
    – rtaft
    Jan 14, 2022 at 19:28

1 Answer 1


The simplest, cheapest thing to do is to intercept that moisture at the source: remove the bulk of it from the vehicles outdoors. I use a floor squeegee to push the snow off of my vehicles (This is its exclusive use so that I don't have to worry about it picking up debris that could scratch a vehicle's paint.) It's usually not too difficult to kick away the snow that accumulates behind each tire too.

Next, air doesn't hold a tremendous amount of heat energy. If you hold the garage door open for a time (several minutes to half an hour) you could flush out all the air and the water vapor contained within it, without losing too much of the heat that's contained in the concrete floor, the walls, the vehicles, etc. This bulk-flush approach may actually remove moisture and retain heat better than a full-time small vent would.

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