Ridge vents v.s. attic fans?

[Charlie99]

I put in a ridge vent that runs the length of the roof into a house in Sunnyvale about 3 years ago. It does a pretty good job of venting excess heat from the attic. It's hard to do a direct comparison though, because it was installed with a dimensional composition (similar to asphalt) roof that replaced a shake roof. The triple layer dimensional shingles are a lot better insulator than the old cedar shakes.

Another type of fan that you should consider is a large capacity fan that sucks in air from the ceiling of a hallway and exhausts it up through the attic. This does wonders for cooling off the house once the summer sea breeze finally works its way down the bay to Sunnyvale around 3PM. IIRC, it's about a 1/2 hp motor with about 2' diameter fan. It draws air from the living area of the house via a set of spring loaded louvers that snap back shut when the fan is off. It's a good alternative for house cooling in places where the evening and nighttime temps are nice and cool even in mid-summer.

 

[cool_hardware52]

I put in a ridge vent that runs the length of the roof into a house in Sunnyvale about 3 years ago. It does a pretty good job of venting excess heat from the attic. It's hard to do a direct comparison though, because it was installed with a dimensional composition (similar to asphalt) roof that replaced a shake roof. The triple layer dimensional shingles are a lot better insulator than the old cedar shakes.

Another type of fan that you should consider is a large capacity fan that sucks in air from the ceiling of a hallway and exhausts it up through the attic. This does wonders for cooling off the house once the summer sea breeze finally works its way down the bay to Sunnyvale around 3PM. IIRC, it's about a 1/2 hp motor with about 2' diameter fan. It draws air from the living area of the house via a set of spring loaded louvers that snap back shut when the fan is off. It's a good alternative for house cooling in places where the evening and nighttime temps are nice and cool even in mid-summer.

That's called a "whole house fan" They are designed to pull ambient air in through the windows into the living space, and exhaust the air in the house into the attic. The hot air in the attic is then forced out through whatever vents there are in the attic.

Down here in the "Banana Belt" (San Gabriel Valley in SoCal) I use both a thermostatically controlled Gable vent fan, ~1/5 HP, and a Whole House fan.

During the day the Gable vent fan dumps the hot air in the attic out a Gable vent, and draws in ambient air through the rest of the Gable vents. That keeps the attic temps down to about 125 degrees F. That greatly reduces the heat load on the conditioned space below, and reduces the heat stored in the mass of the attic, ceiling, roof structure etc.

In the evening after the ambient temps have dropped below the temps in the conditioned space, which is typical about the time I arrive home, I can open the windows and run the whole house fan for about 20-30 minutes. On a 100 degree day in August the house will be about 85-90 inside when I arrive home, but it will be maybe 75-80 outside. With the whole house fan I can pull the house and attic down to ambient, or close to it.

Now my AC only has to drop the conditioned space from 75-80 down to ~70 instead of having to drop it from 90. That's a huge difference.

Tobin

 

[syntaxerrorsix]

Tobin has the correct answer. The "whole house fan" is really the way to go if you already have typical venting from soffits and ridge vents. Flow is the key. My cats however would not be appreciative to 90 degrees inside while I'm at work therefore AC stays on daily. Sure would like to reduce my bill like that though.

 

[pablordstribe]

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