Heat and humidity in the attic
If there is one line in a Florida roofing quote worth arguing about, it is this one. The attic decides whether the shingles above it reach their rated life or retire five years early, and in this climate it does so through two separate mechanisms, one of which almost nobody expects.
- 1 Ridge caps. Full sun, no shade, ever. They cook before anything else on the roof does.
- 2 The field. Shingle, or tile sitting on felt that is doing the actual waterproofing.
- 3 Valleys. Two slopes emptying through one line, every single afternoon.
- 4 Flashing. The metal salt air finds long before it touches the covering.
- 5 The vent boot. Rubber baked brittle by sun, and the bay area’s most ordinary leak.
- 6 Eaves. Where the Florida room ties in, and where the hardware corrodes first.
Heat, and then the surprise
The heat part is straightforward: an attic that cannot exhaust runs far above outdoor temperature through a long summer, and it holds that heat against the underside of the deck all day. The covering ages from below while the sun works on it from above, and cooling costs rise at the same time.
The surprise is moisture, and it works backwards from what people assume. In most of the country, attic condensation is a winter problem caused by warm indoor air rising into a cold attic. Here it is a summer problem in reverse: hot, humid outdoor air meets surfaces cooled by air-conditioned ductwork, and condenses on them. Ducts sweating in an attic, damp insulation around them, and staining on the deck near supply lines are all signs of it, and none of them start with the roof.
Balanced, and done on replacement day
Ventilation is a pair rather than a product: intake low at the soffits, exhaust high at the ridge, sized to each other so air actually moves. The common failures here are ridge exhaust with no matching intake, and soffit vents buried under insulation. Exhaust without intake pulls conditioned air up out of the house instead of drawing outdoor air through, which makes both problems worse.
Correcting it while the deck is open costs a fraction of retrofitting later. On the region’s 1990s and 2000s production housing, where builder-minimum ventilation met code and stopped there, this is the single line most worth paying extra for. “We reinstall the existing vents” is not a ventilation scope.
Want this looked at?
Call (866) 227-2038Say what you have noticed and you will be connected with a provider covering your county.