Worker applying spray foam insulation in an unfinished attic.

Attic Insulation

Two Effective Ways to Insulate Your Attic with Spray Foam in South Florida

At Ocean Spray Foam Pros, we commonly use two methods to insulate attic spaces with spray polyurethane foam (SPF), both designed to protect your home from heat, humidity, and moisture-related damage:

1. Traditional Method: Attic Floor Spray Foam (Vented Attic)

This approach follows conventional building science and is typically used when architects or builders specify vented attics. Spray foam is applied between the attic floor joists—where fiberglass or cellulose might traditionally go—creating a barrier that insulates the ceiling from extreme temperatures. However, the rest of the attic remains uninsulated and is ventilated through soffit, ridge, and gable vents.

This is the most commonly used system nationwide, although not the most efficient for energy savings or moisture control. In a South Florida climate, a vented attic can reach temperatures of 130°F or more, putting added strain on your air conditioning system and ductwork. This setup can also lead to condensation and moisture-related issues inside the attic.

2. Sealed Attic System: Spray Foam on the Roof Deck (Unvented Attic)

This is considered by many in the spray foam industry to be the superior method—especially in hot, humid climates like ours. Instead of insulating the attic floor, we apply spray foam directly to the underside of the roof deck, sealing off the attic entirely. Foam is applied between roof rafters, along gable ends, and around soffits and eaves.

By turning the attic into a conditioned space, it stays as cool and comfortable as the rest of your home. This helps reduce energy loss, improve HVAC efficiency, and eliminate common problems like ductwork overheating or moisture buildup.

Some builders have raised concerns that sealing the attic could cause roofing shingles to overheat or that wood "needs to breathe." However, modern research and manufacturing practices, like kiln-drying and sealing wood for furniture, contradict this. In fact, sealed and protected wood typically lasts longer. And according to GAF, one of the leading roofing manufacturers, their shingles are fully compatible with unvented roof systems.

Benefits of a Sealed Attic in South Florida:

  • Energy Efficiency: Less heat enters your home, and your AC runs more efficiently.

  • Improved Indoor Air Quality: Keeps out dust, allergens, and loose insulation particles.

  • Better Duct Performance: Conditioned attics minimize heat loss and duct leakage.

  • Lower Utility Bills: Reduced temperature difference means less energy is required to cool your home.

  • Enhanced Comfort: The attic no longer acts like a giant heat trap.

In hot, humid climates like South Florida, applying spray foam insulation directly to the roof deck can reduce attic temperatures by up to 40°F. That significantly lowers the heat transferred into your living space, reducing both energy costs and wear on your HVAC system.

For more detailed building science behind vented vs. sealed attics in hot climates, check out the ASHRAE publication, “Vented and Sealed Attics in Hot Climates” or give us a call—we’re happy to walk you through the best option for your home.