Energy efficient windows in Florida: what numbers to look for

The short answer

Look at two numbers on the window's label or spec sheet. ENERGY STAR's page for the Southern climate zone lists a U-factor of 0.32 or lower and an SHGC of 0.23 or lower. The criteria came from ENERGY STAR's page for Broward County, Florida. Look up your own county on the ENERGY STAR website to confirm your zone.

A window can meet the energy numbers and still need a separate hurricane rating, and the reverse is also true. Treat them as two questions with two documents.

What the two numbers mean

• U-factor measures how much heat passes through the window from the warm side to the cool side. A lower number means less heat moves through.
• SHGC, the solar heat gain coefficient, is the share of the sun's heat that gets through the glass into your home. It runs from 0 to 1. A lower number means less sun heat comes in.

Florida has a long cooling season, so the sun coming through the glass is the main thing to control. That is why SHGC is the number to watch closely here. The Southern zone limit of 0.23 is a low number on purpose.

Watch the date on older guides

If you read an older article or a publication from a university or a utility, the numbers it lists may differ from the ones above. Check the page date, and confirm the current numbers on the ENERGY STAR website before you rely on any figure you find.

We also could not confirm the values for ENERGY STAR's top tier, called Most Efficient, so we do not list them.

Energy ratings and hurricane ratings are separate

In Florida most window projects raise a second question: will the glass hold up to wind and flying debris? That is answered by impact ratings, not energy ratings. The Florida wind mitigation form, OIR-B1-1802, asks about opening protection and spells out the test standards, including ASTM E1886 and ASTM E1996. It sets the top levels, A and B, for products that pass those tests and are listed in the Florida product approval system or by Miami-Dade County.

Ask for both: the energy numbers and the impact approval for the exact window you are buying. Our guides on impact windows vs shutters and Florida product approval explain the second part.

Will energy windows lower your insurance?

Not through their energy numbers. The wind mitigation form has nine questions: building code, wind region, roof slope, roof covering, roof deck attachment, roof-to-wall attachment, roof shape, sealed roof deck, and opening protection. None of them ask about U-factor or SHGC.

Opening protection can matter, and the insurer sets any credit. Florida law, Section 627.0629(1), says credits for qualifying features must be in the insurer's rate filing, and insurers must post their hurricane mitigation discounts on their websites. We never promise a percentage, because it varies by insurer. The form itself says some items may not qualify for a discount. See our wind mitigation guide.

Cost and savings: what we cannot say

We did not find a current, official figure for how much a low-SHGC window saves on a Florida cooling bill, so we are not giving one. Be careful with any ad that promises a percent. Ask the seller to show the source and the home it was measured on.

For costs, see our guide to impact window cost and insurance. Your own price comes from a written estimate after an on-site visit.

How to read a window quote

A good quote names the exact window, not just the brand. Ask that it list the U-factor, the SHGC, the impact approval document, the frame and glass type, the size of each opening, and who pulls the permit. Compare quotes line by line. Two windows with the same brand name can have different numbers.

If a quote says a window is energy efficient but gives no numbers, ask for the spec sheet. The numbers on it should be at or below 0.32 for U-factor and 0.23 for SHGC if you want to match the Southern zone criteria.

Other ways to cut sun heat

Glass is only one part of the picture. Shade that stops the sun before it reaches the window helps too. A covered lanai or an overhang over a west-facing wall, for example, blocks sun that would otherwise hit the glass. See our page on outdoor living areas for covered structures.

We did not find a verified savings number for any of these, so treat them as options to discuss, not as promises. A contractor who walks the house with you can see which walls get the most sun.

How Hildebrand handles window replacement

Hildebrand Construction & Remodeling is a family-owned Florida licensed general contractor in Palmetto (Certified Building Contractor, license CBC1257253). We install impact windows and doors, pull the required permits, and meet Florida Building Code inspections. See our impact windows and doors page.

We start with a free in-home consultation and a written estimate. The price does not change without your written approval. Manufacturer warranties are passed through. If you have an HOA, you file the application and we provide the specs and drawings.

Questions homeowners ask