Massachusetts roofer Jim Lydon once got a call from a client complaining that the roof Lydon had installed was “leaking like a sieve.” When he arrived to inspect, Lydon found that the homeowner, hoping to save money on her fuel bill, had plugged up all the soffit vents.

Not a smart idea. Ventilation systems remove stagnant air and moisture from an attic. Lack of ventilation can result in premature aging of the roof, warping and cracking of the wood framing and roof deck, buckling of shingles and felt, and higher energy costs — not to mention roof leaks and ice damming. Of course, to many homeowners, the concept of a cold roof makes little sense.

“We tell [clients] it should be nice and cold up there in the winter,” says Randy Brown, owner of Clearwater Home Improvement in Mystic, Conn. “What everybody is taught is to keep the heat in the house.”

What's Good Venting? Roofers agree that not enough good things can be said about attic ventilation systems. A good system, experts say, consists of continuous ridge and soffit vents, which provide for air flow from eaves to ridge.

Mike Guertin, author of Roofing With Asphalt Shingles (The Taunton Press) and a Rhode Island contractor, says that homeowners know more about this now than they ever used to, thanks to the Internet. “People do a lot of their own research before I get the call,” he says. “Ventilation is usually one of their concerns.”

Problems resulting from moisture build-up are not difficult to diagnose when conducting a roof assessment. Black mold on the underside of plywood sheathing and moist or rusted nail ends are both telling signs. Brown says that many homes he services have no attic ventilation or, in some cases, have gable vents, but no ridge or soffit venting. He says he often finds it necessary, when re-roofing, to replace a previously installed ridge vent with a more up-to-date system that effectively prevents wind-blown rain or snow entry. He also points out that if Clearwater is replacing a roof and only gable vents exist, the company typically installs a ridge vent to maintain its 20-year warranty on product and labor. Air movement from gable to ridge vent, Brown says, works in most situations.

Day of Reckoning Homeowners who live in ignorance of the moisture problems in the attic may find their day of reckoning when they go to sell. “When the home inspector comes,” Guertin says, “he may red-flag it and end up telling them they have a problem and that the buyer either wants to back out or hold back money in escrow.” In that case, “it becomes an issue they have to deal with quickly.”