The Cheapest Thing That Makes a Roof Last Longer

Shingles are rated for a life in years, and that number quietly assumes the roof is being cooled from underneath. An attic that cannot breathe runs far hotter than the outside air in summer, and asphalt shingles cooked from below age from below — they lose flexibility, the oils migrate out, and they start curling and cracking years before the same product would elsewhere on the same street.

The winter half of the problem is worse and less obvious. Warm, moist air from the house rises into the attic. If it cannot get out, it meets the cold underside of the decking and condenses there. You end up with damp sheathing, and over enough winters, mould and softening — all without a single drop of rain getting through the roof surface. People find it during a tear-off and assume there must have been a leak.

Ventilation works as a system with two halves, and it only works if both are present. Air has to come IN low, at the eaves, through soffit vents, and go OUT high, at or near the ridge. That drives a continuous flow up the underside of the roof. Exhaust with no intake does very little: the vent at the top has nothing to pull, so instead of drawing air from the soffits it pulls conditioned air up out of the house through every gap in the ceiling, which is worse than doing nothing.

The commonest failure we find has nothing to do with the vents themselves. Somebody insulated the attic properly and packed the insulation right out to the eaves, sealing the soffit vents shut from the inside. The vents are still there, still visible from outside, and completely blocked. Baffles at the eaves are the fix and they cost very little; the point is that a roof can be perfectly ventilated on paper and have no intake at all.

There is also such a thing as too many kinds of exhaust. Mixing ridge vents with gable vents, or with powered fans, can short-circuit the flow — the ridge vent starts drawing air from the gable vent a few feet away instead of from the soffits, and the far end of the attic gets no movement at all. One exhaust type, sized for the attic, beats three types fighting each other.

You can check some of this yourself. On a hot day, put your head into the attic: it will be warm, but it should not be dramatically hotter than outside, and there should be perceptible air movement. In winter, look for frost on the nail points coming through the sheathing — that is condensation, and it means moist air is sitting up there. And from the garden, check whether the soffits actually have vents in them, because plenty of houses have soffits with no openings whatsoever.

Ventilation is worth sorting out at the same time as a roof, because the decking is exposed and the intake and exhaust can both be corrected for a fraction of what they cost as a separate visit. If you are already thinking about a roof, message us on WhatsApp at (309) 336-9329 or send the details through the form on this site and ask about the attic at the same time.