Fixing Roof Ventilation While the Hail Roof Is Open

On a July afternoon, an attic with poor airflow can run far hotter than the air outside. That heat cooks the shingles from underneath, drying out the asphalt and making them brittle years ahead of schedule. A brittle shingle cracks under hail that a supple one would shrug off.

Winter flips the problem around. Warm, damp air from showers and cooking drifts into the attic, condenses on the cold underside of the decking and soaks the wood. On tear-offs we regularly find plywood stained dark over a badly vented section while the well-vented part of the same roof is clean. Same shingles, same storm. Different air.

Air has to enter near the bottom of the roof and leave near the top. Intake usually means soffit vents under the overhang. Exhaust usually means a continuous ridge vent, box vents near the peak, or a powered fan. Outside air comes in at the soffits, sweeps along the underside of the deck and exits up high.

The mistake we run into most is plenty of exhaust and almost no intake. Soffit vents get painted shut or buried under blown-in insulation. A ridge vent with nothing feeding it pulls air from wherever it can, including the rooms below through light fixtures and attic hatches. That drags conditioned air and household moisture straight into the attic. Adding exhaust won't fix it. Opening the intake will.

The second mistake is mixing exhaust types on one roof. A ridge vent and a few box vents a short distance apart can short-circuit each other, one drawing air in through the other while the lower attic sits stagnant. On a replacement we normally pick one exhaust system and close off the rest.

With the shingles stripped, cutting a ridge slot takes minutes. Closing an old box vent hole takes a scrap of decking. Baffles at the eaves, which keep insulation from choking the soffits, can go in from above before the deck is covered. Each of those tasks costs more later as a standalone job, because someone has to pull and relay shingles to get at it.

Hail also beats up the vents themselves. Metal box vents and turbine heads dent and split, and plastic ridge vent can fracture the way a shingle does. Soft metal on the roof is one of the ways an adjuster confirms stone size, so damaged vents usually belong in the claim already. Our page on hail damage to skylights and vents covers how they get documented.

Shingle manufacturers spell out ventilation requirements in their installation instructions, and inadequate ventilation is a familiar exclusion in their limited warranties. A brand-new roof over a stuffy attic can start life with weakened coverage. As an Owens Corning Platinum Preferred contractor, we install to the manufacturer's requirements, and our own workmanship warranty sits on top of theirs. The steps of a full job are laid out on our roof replacement page.

An insurance estimate typically puts back the vents you had: so many box vents, so many feet of ridge vent. If the old roof had no ridge vent, the carrier usually isn't obligated to add one, unless local code requires it on a reroof and your policy includes ordinance or law coverage. Converting box vents to a ridge system, cutting in soffit intake or installing baffles is often an out-of-pocket upgrade.

In our experience it's among the better places to spend a few dollars on a new roof. We price it as its own line so you can decide with the numbers in front of you. The insurance claim page explains how those upgrade lines sit alongside what the policy pays.

We don't sell powered attic fans as a cure for an attic starved of intake. A fan pulling against blocked soffits draws air out of the living space, which raises cooling bills and, in some houses, can pull exhaust from a gas water heater back down its flue. When a home needs more airflow, the answer is almost always more intake first. Recommending nothing beats selling a fan that makes the house worse.