Powered attic vents

slowrev · Jul 1, 2004

Has anyone seen studies on the powered attic vents. Do they really save on AC costs over adequate natural flow type of attic ventilation. Or do they just cost more to buy/replace, and electric consumption. Also they are noisy. I prefer the low cost natural quiet way but if the powered ones really save money then I will go that route.

Ben

BB_TX · Jul 1, 2004

Haven't seen any studies on it. I installed a powered ventilator myself many years ago. When we had the house reroofed a couple years ago, they put in 2 wind turbine ventilators in addition to the powered one. Mine is not noisy. I never notice when it is running and not unless I am in the back yard just below where it is located. It runs on a thermostat cycling on/off based on attic temp, and will run when there is not enough wind to turn the wind turbines. My guess is it saves more electricity than it uses.

California · Jul 1, 2004

If the attic is insulated and vented to modern standards I don't think it will do much.

For about the same cost I prefer a 'whole house fan'. This is a 36 inch exhaust fan in the hallway ceiling, with louvers that are sucked open when the fan is on. When you turn it on you can draw a large volume of cool air into every window in the house at the same time.

In hot weather we run it any time the outside temperature is lower than inside. Usually this is after sunset, or midnight to dawn in the hottest weather.

This accomplishes a lot more than just a pleasant breeze in the house - what it really does is chill the structure and furnishings so the house stays cool all day long. I've only used the A/C one day this summer, when we neglected to run the fan one morning.

I think it is far more energy efficient to chill the house with cool outside air at night, compared to running the A/C all day.

slowrev · Jul 1, 2004

California,
Due to the high summer humidity and hot summer nights in KY the whole house fan thing is not a good option for me. I grew up with one of those and spent many miserable summer nights.
Mold will actually grow on your books and stuff if you do not control the humidity here.

slowrev · Jul 1, 2004

BB,
I had a powered gable vent in NC qand it was noisy. Well noisy is a relative term, what is not viewed as noisy in an urban environment could be viewed as noisy in a country environment where you can hear a car go by on a road 3 miles away in the evening. Are some quieter than others. I was just looking thru the latest Lowes sale flier and saw several powered vents advertised, some solar ??

Bird · Jul 1, 2004

It's been quite awhile (1977 to be exact) since we bought our last new house, and I discussed the topic of roof vents with a local fire captain, who recommended I stay away from the powered ones and use the wind turbines instead (which I did). His reasons were that the powered ones use electricity (admittedly very little), they frequently quit working, but the homeowner doesn't notice it and doesn't get them fixed (just as some people fail to replace dead batteries in smoke detectors), and he said they strongly suspect that a lot of house fires are started by the wiring to the powered roof vents. He did say that he had no proof or real evidence they caused fires; only his and some other firemen's suspicion.

slowrev · Jul 1, 2004

Thanks Bird, Makes sense. I wondered about that in my NC house. A fan that draws about 2 amps wired to a 20 amp circuit = lotsa smoke before a breaker trips. Call me paranoid, but I put a 5 amp inline fuse in the junction box where the fan hooked up, while I was wiring a couple of attic lights up. I would just sort of hate for my house to burn down .

BB_TX · Jul 1, 2004

The powered gable vent fans I have seen (heard?) were noisy. But they were pretty good size fans. Mine is one of the small (24" dia??) dome vent fans that go on top of the roof. You can buy different sizes based on attic footage. You have to cut a hole thru the roof. Mine is not noisy at all, again relative, but I do live outside of town. As Bird mentioned about them quitting working, I did have one quit working several years ago because of a bad thermostat. It ran so quiet that I did not realize it had quit running.