attic fan


Old 12-27-14, 08:21 AM
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attic fan

I have an attic fan that exhausts to part of attic that used to have a large turbine vent Last roof replacement it was removed. Now only place for fan exhaust to go is out ridge vents or gable vents. Concerned that will provide for enough air flow. Fan is thermostatic controlled. Would it be possible to use dimmer switch to slow down fan speed and reduce air flow. Fan serves as a whole house exhaust fan in warmest months
Old 12-27-14, 08:29 AM
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Good that they had the foresight to remove the whirlybird. You will have adequate ventilation through the ridge vents and gables, no worry. Motors of that type don't like dimming controls. You may find a stepped motor controller that has positive positions as far as fan speed goes.
Old 12-27-14, 08:54 AM
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A whole house fan venting into an attic will pressurize that space and if the attic to house ceiling is not very well sealed the results will be some of that hot air being pushed right back to where you don't want it. The more restrictive the exhaust path and the larger the fan, the greater the pressure.

In most cases, a well air sealed attic and lots of insulation will prevent the heat that builds up in the attic from affecting the house below. If you are exhausting warm air from the house, different story.

Be careful with whole house fans as they are often powerful enough to backdraft naturally drafted appliances like a gas water heater or even a furnace during fringe months.


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