Asphalt shingles are designed to withstand direct UV radiation, but they are highly vulnerable to convection heat pressing against them from underneath. A poorly ventilated, under-insulated attic effectively turns your roof deck into a frying pan.
The "Baking" Mechanism
- 1 In July, the sun heats the exterior shingles to 160°F. The heat transfers through the wood deck into the attic.
- 2 If the attic has clogged soffits and degraded floor insulation, the attic cannot exhaust that heat. It pressurizes to 150°F inside.
- 3 Because heat always moves to cold, and the 150°F attic air has nowhere to go, it begins pressing upward against the underside of the roof deck at night. The shingles are now being continuously baked from both sides simultaneously 24 hours a day.
The Symptom: Curling
When asphalt shingles are cooked from beneath, the petroleum oils bake out of the tar quickly. The edges begin to physically curl upward, breaking the watertight seal and exposing your home to massive wind-driven rain leaks.