Attic Fan, Should I get one?

[feet_]

noticed my upstairs in my 2 storey house is hotter than the ground level.
should i install a attic fan?
1/2 the roof faces south.

house is 4 years old

[arisk]

What do you refer to?

My best guess is a "whole house fan", which mounts in the ceiling and sucks air from the living area into the attic.
You might mean a powered roof fan though, which sucks air from the attic to the outdoors.

I've had both and suggest neither.
I've removed both.

The whole house fan seemed like a wonderful idea until actually put into use.
It is difficult to seal and insulate adequately in cool weather.
Their origins are warmer climates, where I'm sure they work better.
I suspect what I gained in the summer on AC costs, I lost in the winter on heating.
It was nice to open lower level windows as temperature cooled in the evening and purge the hot air in the house though.
It was also very noisy.

The power roof vents don't last very long before they seize up, and of course require electricity to run.

In the end, I was just as ahead running AC as required

[aqnd]

noticed my upstairs in my 2 storey house is hotter than the ground level.

You can fight physics all you want, but your second level will always be warmer because hot air rises.

If there is excessive heat buildup in the attic, it may help. But if the heat is coming from anywhere but the attic, it will do nothing for you.
You need to balance AC ducts (if using AC), get blackout curtains, whole home air circulation (some people run the furnace fan a bit), etc.

[venice_it]

I have a bit of an amateur set up but it works well. My attic access is in my linen closet on the top floor and for the spring- fall period I remove the insulated attic access panel and put another panel that has a fan installed. When in use, I have to prop open the linen closet door a few inches so the fan has adequate air flow. The fan is about 350 cfm, so not massive, but on warm days it is noticeable whether it is on or off by how the house feels.

When the a/c is running, I shut the fan down and leave the linen closet door closed.

I think the the system works well as the hottest air is exhausted and cooler air is drawn in through the windows. The hot air from the house being exhausted into the attic is much cooler than the attic air, thus further helping reduce attic temperatures which should help lower the home temperature. It should also extend the life of the roof and reduce days that you need to use the a/c.

I do believe in using the a/c when necessary and have a lot of ceiling fans as well as power vent the attic air outside on hot days. You simply can't beat an a/c for humidity reduction and cooling on very hot days, but if you can create good air flow throughout your home you can reduce the days you need to rely on a/c.

[RETD]

I have a bit of an amateur set up but it works well. My attic access is in my linen closet on the top floor and for the spring- fall period I remove the insulated attic access panel and put another panel that has a fan installed. When in use, I have to prop open the linen closet door a few inches so the fan has adequate air flow. The fan is about 350 cfm, so not massive, but on warm days it is noticeable whether it is on or off by how the house feels.

When the a/c is running, I shut the fan down and leave the linen closet door closed.

I think the the system works well as the hottest air is exhausted and cooler air is drawn in through the windows. The hot air from the house being exhausted into the attic is much cooler than the attic air, thus further helping reduce attic temperatures which should help lower the home temperature. It should also extend the life of the roof and reduce days that you need to use the a/c.

I do believe in using the a/c when necessary and have a lot of ceiling fans as well as power vent the attic air outside on hot days. You simply can't beat an a/c for humidity reduction and cooling on very hot days, but if you can create good air flow throughout your home you can reduce the days you need to rely on a/c.


This sounds like an interesting setup. How do you power the fan? Hopefully not with an extension cord that runs through the hallway all summer. One could get a similar though partial effect by running the bathroom exhaust fans though that wouldn't help purge the attic space.

I've considered powered attic exhaust fans but dismissed them because of the cost (capital and operating), questionable reliability and hassle/cost of repairs in case they fail. While the idea sounds good in principle I wonder how much heat gain you would actually reduce coming in via your attic as your attic is generally the best insulated area of the house. Running the a/c a bit longer is probably the most cost effective solution.

One could also install a whirly-bird turbine exhaust vent but those work best when it's breezy and they are ugly as sin. Bearings do go on those units too but they do seem to last quite a while before they fail.