By Dwight Barnett
Scripps Howard News Service
Question: I built my house with ridge and soffit vents for ventilation in my walk-up attic, which contains about 1,000 square feet. However, the temperature in the attic sometimes climbs beyond 120 degrees. Would an attic fan help, in conjunction with the combination of the ridge and soffit vent system? In a recent column you wrote, "You can use a fan with gable, canned or soffit vents or any combination of the four, but not with ridge vent."
Answer: If you install a roof/attic fan and the home has a ridge vent, the fan would pull air through that portion of the ridge vent closest to the fan. Therefore, the soffit areas below the fan and the ends of the attic with gable vents would have little or no airflow.
Do not use a vent fan, canned vents or turbine vents with a ridge vent. The ridge vent is designed to promote airflow from the soffit vents. Because air is leaving the attic space, outside air needs to enter in to replace it. This "make-up" air enters each soffit vent, where the make-up air absorbs heat from the attic, rises to the ridge vent and, voila, you have free thermal attic ventilation.
In winter, cool, dry air enters the soffit vents, absorbs warm moisture from the attic and vents through the ridge vent. An attic fan that has a thermostat would not be working in cooler temperatures, and all the moist attic air would remain to be a source for mold and decay.
Along with proper venting, make sure the attic floor is well-insulated to avoid thermal airflow being from the home's living areas and not from the soffit vents. Conditioned air from the home will exit through the ceiling and out through the ridge vent, wasting energy without proper attic floor insulation.
(Dwight Barnett is a master inspector certified by the American Society of Home Inspectors. Questions may be addressed to him at P.O. Box 14091, Evansville, IN 47728, or e-mail dbarnett@insightbb.com.)
