The best ways to vent an attic
Q: We're about to have a new shingle roof installed, but our roofing contractor says out attic is not adequately vented. We currently have a ridge vent and a power exhaust fan on the roof, but our contractor says we should eliminate the ridge vent. Is this good advice? If not, what do you recommend for attic ventilation?
A: Most attics are marginally vented, because minimum requirements for attic ventilation are truly minimal. This can be verified by entering an attic on a hot summer day. Insufficient attic vents can increase heat gain in a home, driving up the air conditioning costs, while shortening the useful life of composition roofing materials.
Industry studies of attic ventilation, published in the Journal of Light Construction, have shown that the best type of ventilation is soffit and ridge venting. This involves the natural process of convection: the tendency for heated air to rise. In this case, hot air in the attic rises through the ridge vents and is replaced by cooler outside air that is drawn into vent openings in the eaves. The more heated attic air becomes, the more quickly it vents outward at the ridge and is replaced at the lower vent openings. In these same studies, it was found that power fans provide the least effective ventilation, no matter where the fans are placed.
Another effective means of convecting hot air from an attic involves air turbines - those round spinning devices commonly seen on the roofs of commercial and manufacturing buildings. Turbines can also outperform mechanical vents, as long as there are vent openings in the eaves.
Q: Before buying my home, I hired a professional inspector. He said something was wrong with the heating and air conditioning system and recommended review by an HVAC contractor. The seller had his home warranty company check the system and they left a receipt saying that it was in working condition. Shortly after moving in, the system stopped working. The warranty company came out again and said that the problem is not covered because it is a preexisting condition. How can they say that when they found it to be ok just a few months ago? How can I get them to honor this claim?
A: The home inspectors recommendation was "review by a licensed HVAC contractor," not by a warranty company. Unfortunately, that advice was not followed.
If the warranty company inspected the HVAC system and certified it as operative, they cannot justifiably claim that the current problem is preexisting. Hopefully, you kept a copy of the receipt that declared the system to be functional. If they refuse to take responsibility for their previous finding, you should file a complaint with the state agency that regulates insurance companies.
• Email Barry Stone, certified building inspector, at barry@housedetective.com.
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