We have a typical 24'x44' raised ranch with a "Hip Roof" with two 8'' box vents ..one on each end and no soffit or ridge vents... = Hot attic.
We also had a remote reading thermometer in the attic
before and
after we had a
Master Flow attic fan installed. Before the fan, the temp in the attic in the afternoon would typically be 145+ degrees on sunny days in August. Without the forced ventilation that temp would pretty much remain until 5:00 AM the next morning. It was like a Hot Blanket above all the rooms in the house.
After we added the fan AND 16 soffit vents under the wide roof overhangs, the temp rarely goes over 107 degrees on the hottest days. The fan was less than $100 at Home Depot. We had the fan installed when the roof was re-shingled in 2003. The fan has a thermostat in the attic which turns the fan on at about 90 degrees and there is a manual shutoff switch in the utility room.
BTW: The old 8" box vents were Eliminated and we Did Not have "Ridge Vents" installed as they would interfere with the airflow with the new fan. NB
Hip Roof: http://en.wikipedia.org/wiki/Hip_roof
Master Flow: http://www.gaf.com/Roofing/Residenti...entilator.aspx