If your electric bill keeps climbing every summer, your attic's R-value is one of the first things worth checking.
What is R-value?
R-value measures how well insulation resists heat flow — the higher the number, the better it slows heat moving through your ceiling and walls. In Florida the goal is keeping blistering attic heat out of the living space, so a higher attic R-value means your AC works less and your home stays cooler longer.
How much R-value do Florida attics need?
The U.S. Department of Energy places most of Florida in Climate Zones 1 and 2. For attics, DOE recommends roughly R-30 to R-49. Many older Cape Coral and Fort Myers homes were built with as little as R-11 to R-19 — and that insulation has usually settled and compressed, dropping real-world performance even lower.
Rule of thumb: if you can see the tops of your ceiling joists across the attic, you almost certainly need more insulation.
R-value by insulation type
- Closed-cell spray foam — ~R-6 to R-7 per inch; highest R-value per inch and it air-seals as it expands.
- Open-cell spray foam — ~R-3.5 to R-3.7 per inch, great air sealing and sound dampening.
- Blown-in fiberglass — ~R-2.2 to R-2.7 per inch; fast, even attic coverage.
- Blown-in cellulose — ~R-3.2 to R-3.8 per inch; dense and eco-friendly.
- Fiberglass batts — ~R-3 to R-4 per inch; ideal for walls and new construction.
R-value isn't the whole story
In our humid climate, air sealing matters just as much. Gaps around can lights, plumbing, and the attic hatch let hot, moist air pour in and undermine even thick insulation, which is why we pair insulation upgrades with air sealing.
Related: Insulating CMU block walls · What is batt insulation?