Why your attic is killing your roof

Most roofs die from underneath

When a twenty-year roof fails at year twelve, the shingles are usually blamed and the attic is usually responsible. Heat and moisture trapped under the deck cook the roof from the inside, and nothing you buy at the material end will stop it.

The frustrating part is that ventilation is cheap. It is the single most cost-effective thing a homeowner can fix, and it is the thing almost nobody is told about until the second roof.

‍

Exhaust without intake is decoration

A ridge vent only works if air can get in at the soffits to feed it. Install the ridge vent alone — which happens constantly — and the system pulls air from the easiest available opening instead, which is usually your living space through the ceiling.

That is why we go into the attic before quoting. Blocked soffits, insulation shoved tight against the roof deck, and a bathroom fan venting into the roof space rather than out of it are the three findings we make most often, and all three are cheap to correct.

What a badly vented attic looks like

You can usually diagnose it from inside on a cold morning, with a torch and ten minutes.

• Rusted nail tips poking through the sheathing — that is condensation, not a leak
• Dark staining or fuzzy growth on the underside of the deck
• Insulation packed hard against the roof, sealing the soffits shut
• Ice building along the eaves in winter while the rest of the roof stays clear

‍

Ice dams are an attic problem

Heat escaping into the attic melts snow on the upper roof. The water runs down to the cold overhang, refreezes, and builds a ridge that backs meltwater up under the shingles. Nothing about that sequence starts on the roof surface.

You cannot solve an ice dam with better shingles. You solve it with a colder attic, which means air sealing first and ventilation second.

Which is why heated cables are a symptom-management tool rather than a fix. They keep a channel open through the ice; they do nothing about the heat loss that made the ice.

Fix it while the roof is off

Balancing ventilation during a replacement adds very little to the job. Doing it afterwards means going back up, cutting the ridge again, and paying twice for the same access.

Ask any contractor quoting your replacement what the intake-to-exhaust ratio will be when they finish. If the answer is a shrug, or a ridge vent with no mention of the soffits, keep looking.