Too many vents on roof
Q: I recently had a new roof installed and the roofers included a ridge vent at the peak of the roof. Now I understand a ridge vent should not have been installed because I already had the flat roof vents, gable vents and overhang vents. Should I be concerned?
A: The main problem you might experience is unbalanced ventilation. When winds pass over the roof, the ridge vent could, under certain conditions, allow rain or snow to enter through the ridge vent to the attic space. According to Cor-A-Vent, a leading manufacturer of venting products, “When installing a ridge vent system, all other vent openings (except soffits) must be closed off.”
By using a ridge vent balanced with an equal amount of soffit vents, each rafter space in the attic will be ventilated.
How does this work? When the wind is blowing over the roof, the attic is under a negative pressure. To equalize the pressure between the outside air and the interior of the attic, air enters through the soffit vents and travels up through the spaces between the rafters where it exits through the ridge vent removing warm moist air from the attic.
If your home also has a gable vent, canned vent, electric fan or turbine vent -- or any combination of these -- the thermal airflow will be interrupted and the ridge vent can become an intake opening.
Where possible, the gable, canned and turbine vents should be sealed from inside the attic using cardboard, foam board or blankets of fiberglass insulation.
If the attic has a power ventilation fan, the fan should be disconnected from the electrical service by a qualified electrician before the opening is sealed. When having a roof replaced, make sure the roofing contractor understands the problems associated with mixing types of vents and either removes or seals unwanted vents if a ridge vent is to be installed.Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 268, Evansville, Ind. 47702 or email him at d.Barnett@insightbb.com. Scripps Howard News Service