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Old 05-28-2009, 10:33 AM   #1
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attic ventilation

I have read several articles recently on the ineffectiveness of powered attic ventilation.........however my home is older with no soffits (so no soffit vents) and only two passive gable vents. Articles seem to indicate that to much air removal via powered ventilators can suck cold A/C air out of your home therby increasing your A/C usage, as well as the constantly running vent fan (increasing your electric bill even further) that will have little impact on the temp in your it worth having any powered ventilation in this attic (perhaps something not powerful enough to suck all the air out of the home , just the attic) or adding a rigde vent or any other type of passive ventilation not requiring soffit vents????
It gets very hot up there in the summer and I am putting a new energy star rated shingle on the roof , but am unsure about improving the ventilation.


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Old 05-28-2009, 03:41 PM   #2
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There are solar powered vents.

If your home is insulated correctly, then how can the power vent suck the cool air out?


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Old 05-28-2009, 04:55 PM   #3
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I agree with previous post. Unless there is a physical connection between your house and the attic, there is no way for air within the house to be sucked out through the attic. In my house, I do not have central air, but I do have a power attic fan in one of the gables. Essentially the fan draws relatively cooler air from the far gable vent through the attic, and out through the fan (which is in the gable).

The fan is set to start when the attic gets above 95 degrees F, which happens on sunny days in the summer. By drawing cooler air through, the attic can be maintained at not more than 100 degrees, which is still pretty high, but I have a lot of insulation between the second floor of the house and the attic, so there is no problem.
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Old 05-28-2009, 07:23 PM   #4
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You are correct. There are many gaps in the Building Envelope which will allow the interior conditioned, (And Paid For), climatized air to transfer directly from the living quarters to the attic.

Some, but not all, would be the top wall plate, ceiling can lights, exhsust fan penetrations and any outlets cut into the wall areas.

Even if you CAN NOT get a Balanced Amount of Intake Ventilation to correspond to your continuous Ridge Exhaust Ventilation, as long as you choose one with external baffles, such as the Shingle Vent II, or it's knock off, Cobra Snow Country, then the minor forces of air passing over the external wind deflecting baffle will increase the amount of air being discharged from the attic.

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Old 05-30-2009, 06:09 AM   #5
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Older houses will tend to lose air in many places especially if the suction is more than the intake can provide
The newer houses may be a little more difficult.
Got any soffit pictures, maybe the intake could be corrected.
Also out there is a verry good product called Smart Vent but would be best installed with a new roof
Dale Chomechko
DC Roofing Inc
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Old 05-31-2009, 09:33 PM   #6
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The powered gable end fans make a big temp difference in my attic (used for storage) which is both walk in at second story for about 800 sq feet and above the 2nd story for the remaining house. Have continuous vented soffit. In Alabama in summer with fans running in 2 of the 4 gable ends temp stays at 100-105 (fans thermo-Humido stat set around 100 temp and rh at 70%). Without these temps ran 120++ in attic in summer with outside temps 92+. Liked them so well, put one in my garage floored attic also, set at 100F keeps garage cooler during outside temps approaching 90F already this year.


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