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Mon, Oct. 14

Hot Garages - Part II Fans and Evaporative Coolers

Last time I wrote about hot garages. We talked about insulated overhead doors and attic insulation, both of which can help control the temperatures inside garages.

Last year we had insulated overhead doors installed, which helped a lot. Last week we had Advantage Home Performance install R-30 cellulose insulation in our garage attic, which had no insulation. The next morning the garage did not seem much cooler to me. I think it was because the garage kept the heat it already had. I opened all the doors and windows and cooled it off with a large fan, and now we can tell the difference! The garage used to be over 90 degrees on very hot days, now it’s ‘peaking’ at about 83 degrees.

I had an email asking about installing a whole house fan in the garage ceiling. Whole house fans are not that common, but you’ve probably seen one. They are in the ceiling, often in an interior hallway, and usually have a two- or three-speed wall switch. They have louvers that the airflow forces open when the fan is turned on. They are quite noisy, but they can be quite effective at cooling a home. Before you start writing me, I know house fans have gone high tech. There are models with dampers or covers that open electrically, rather than louvers. The new models are much quieter, and some have a fan/blower in the attic and ducts to different rooms.

But whether you have one that looks and sounds like an airplane propeller, or a new auto-damper thermostat controlled fan, you should not install one in your garage! The walls (common with the home) and attics in an attached garage have to be well sealed, to serve as a fire and gas (carbon monoxide) barrier. Even the door from a garage into a home should be metal or solid wood (fire resistant), and should be self-closing with weatherstripping installed.

Installing a fan pulling air from the garage into the attic would pretty much guarantee you’ll lose the whole house if a fire starts in the garage. A fan in a window or an exterior wall would be OK, blowing in or out. There are fans designed for this with louvers to keep out hot or cold air when they are not in use.

I was also asked about using a portable evaporative cooler in a garage. I do not have much faith in these. Everyone knows evaporative coolers don’t work in humid areas - my clients from New Jersey have never even heard of one.

Evaporative coolers need hot dry air pulled over the media to cool the air. So an evaporative cooler in a small room that is recirculating the air, rather than pulling in dry outside air, will quickly increase the humidity in the room. The more the humidity increases, the less an evaporative cooler can cool the air.

Common sense (and science) says eventually it becomes more of a humidifier than a cooler. (I expect some ‘feedback’ from that comment.) A window or wall evaporative cooler in a garage would work much better.

Randy West owns Professional Building Consultants in Prescott. He is state-certified and has performed more than 7,000 home inspections in the Prescott area. West serves on the Home Inspector Rules and Standards Committee for the Arizona Board of Technical Registration. Contact him at randywest2@gmail.com or visit http://inspectprescott.com.

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