Hello, all. We have a 25-30 year old attic fan that is very inefficient at venting air through the attic. We need to do something. What product would you recommend to improve the situation?
The gable vent openings on my roof are very small, otherwise I would get an attic fan from www.jetfanusa.com They're based in Chicago (I'm in NY), so you'd need to get an installer or be handy. Still, the have good reviews online and they actually make the fans in the USA.
The only attic ventilation that has proved truly effective is vented soffits combined with ridge vents. Or converting to an unvented attic if you are in a warm climate.
Attic ventilation is for removing moisture not cooling the attic. An attic fan can draw humid air into the attic so be careful to consider the climate in your location.
To reduce the temperature in the attic add insulation to the rafter bays and/or a radiant barrier.
Here's how it works:
The sun heats up the roof shingles and sheathing and the bottom of the sheathing emits infrared energy into the space without heating the air. When the energy hits the attic floor it heats it and the floor then heats the air. Removing the heated air from the attic space and drawing outside air into the attic might reduce the air temperature of the attic but it does little to reduce the heat gain to the floor below. For that you need insulation and a radiant barrier. Therefore, fans and large openings are not a part of an effective energy conservation system in an attic.
Well, here's a link with a good explanation of how ventilation plays a part...
But a previous answer recommending proper insulation and possibly a radiant barrier is key. But if you already have these, better ventilation will help. My neighbor's thermostat controlled fan would run all day before he added eyebrow vents and soffit vents; now it comes on only in the late afternoon.
Also, if you re-roof, a light colored shingle will help a lot, if you can stand the look. I just went from wood shake to a black asphalt and my attic is now almost degrees hotter.
Here is a link that might be useful: Summer Heat Build-up
The misunderstanding about mechanically cooling attics with fans is very common especially with home inspectors who are often former contractors who are the source of so many specious heating and cooling ideas.
Instead of forcing hot air out of the attic you should be trying to keep the cool air inside the house. If you don't believe me listen to Joe.
Here is a link that might be useful: Lstiburek's Rules for Venting Roofs