Roof Deck & Unvented Attic Insulation in St. Petersburg, FL

Roof deck and unvented attic insulation moves the insulation from the attic floor to the underside of the roof. In many St. Petersburg homes, the air handler and ducts sit in a vented attic. In summer that attic air is far hotter than outdoors, and the ducts running through it pick up heat and can sweat. Foaming the roof deck and closing the attic vents turns the attic into a semi-conditioned space, close to indoor temperature, so the ducts work in cooler, drier air.

Open-cell or closed-cell on the roof

Open-cell foam is the most common choice for roof decks in our climate. It is lighter, costs less and lets the roof deck dry to the inside if a leak ever happens, which also makes leaks easier to notice. Closed-cell foam adds strength and vapor control and suits low-slope roofs and certain assemblies. We pick based on the roof and explain why.

What we check first

Before spraying, we inspect the roof deck from below for leaks, rot and storm damage, check that bath and dryer fans vent outside rather than into the attic, look at gas appliance venting, and remove any wet or contaminated insulation from the attic floor. Some shingle manufacturers have warranty conditions for unvented attics, so check your roof warranty.

Gable walls and the rest of the envelope

An unvented attic works only if it is sealed. That means foaming the gable end walls, closing soffit and ridge vents, and sealing the transitions between the roof deck and walls. We include all of that in the quote.

Cost

HomeGuide lists foam on the roof deck at $1,500 to $9,000, and Fixr lists foaming an existing home's attic at $2,500 to $12,000. Roof size and pitch, foam type and thickness, gable walls and removal of old floor insulation set the total.

Roof replacements

After the 2024 storms many St. Pete homes got new roofs. Once a new roof is on and has been checked for leaks, it is a good time to consider roof deck foam, since the deck is sound and dry.