We have pulled ten-year-old shingles off Franklin houses that looked twenty-five. The shingles were fine. The attic underneath them was not.
Why a roof needs to breathe
A roof assembly works as a system: cool air enters low at the soffits, rises as it warms, and leaves high at the ridge. Interrupt that and attic temperatures in a Tennessee August climb past 150 degrees. Shingles bake from the underside, the asphalt loses its volatiles early, and the roof ages at roughly double speed.
In winter the same blockage traps moisture instead of heat. Warm damp air from the house condenses on cold sheathing, and over a few seasons that is what turns a plywood deck soft.
The most common mistake
Intake and exhaust have to be balanced. The usual failure is plenty of ridge vent and almost no working intake — because the soffits were painted shut, or insulation was blown in over them, or someone fitted decorative vents with no opening cut behind. A ridge vent with nothing feeding it will pull air backwards down through other roof vents and achieve nothing.
The second most common is mixing exhaust types. A ridge vent plus powered fans plus box vents on the same plane short-circuit each other; the fan pulls from the nearest vent rather than from the soffits.
What to check
Go into your attic on a hot afternoon. If it is brutally hotter than outside, look for daylight at the eaves — if you cannot see any, your intake is blocked. Dark staining on the underside of the sheathing means moisture has been sitting there through the winters.
Fixing ventilation during a replacement costs a few hundred dollars. Fixing the roof it destroyed costs considerably more, which is why we check it on every inspection and put it in the report either way.
