Garage dehumidifiers and opening the garage doors.

by Todd Drury
(Redding, CT, USA)

I am noticing a lot of condensation build up on the floor of my garage this spring. This is a two car garage and is opened and closed several times a day, I store my 97 Porsche in one of the bays and would like to control the humidity if possible. Is there any hope of doing so when the doors are opened and closed several times per day?


Hi Todd and thank you for your question.

Opening and closing garage doors does complicate moisture control since water vapor will move from more humid to less humid air if it is allowed to do so.

The most obvious issue here is to minimize the length of time the garage doors are open and I am sure you do that already.

The problem may be less acute than it seems at first since your main concern is to prevent condensation. As it is cooler at night than in the day most of the condensation is formed at night. If your life follows a typical pattern your garage doors probably remain closed from anything between 8 and 12 hours every night during most 24 hour periods.

In addition to removing moisture from the air a dehumidifier will indirectly draw water from the contents and structure of your garage. As humidity falls more of that moisture evaporates and can be removed from the air by the appliance.

It follows that running a dehumidifier in your garage will be effective in reducing if not eliminating condensation despite the need to open the doors several times per day.

To further ensure the protection of your car and other items I would recommend an appliance that has a higher water removal capacity than the floor area or volume of your garage would indicate. In other words if your garage is, say 600 square feet pick a model that is rated for areas of nearer 1000 square feet. That way the unit will remove the water faster and, thereby, counteract the effect of influxes of moister air during the day.

If it was my garage I would set the humidistat at a lower level than I would use in the house, around 40% as opposed to 50%. 40% is needed to give full protection from corrosion.

A final point is that the unit you choose must be able to operate at the ambient temperature inside your garage at those times of the year when you have a problem. If this temperature is less than 60-65 degrees for extended periods a typical portable model will not be fully effective.

I hope this answers your question but please feel free to come back with a supplementary of two if I haven't answered all your concerns.

Tom (Webmaster)

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