How Are Impact Windows Rated? What Florida Homeowners Need to Know

Oct 1

When living in a hurricane-prone state like Florida, protecting your home starts with your windows. But not all impact windows are created equal. If you're considering upgrading, it’s essential to understand how impact windows are rated and what those ratings mean for your home’s safety, comfort, and energy efficiency.

In this guide, we’ll break down the key rating systems that determine a window’s performance, and how to make an informed decision when shopping for replacement windows in Florida.

1. Design Pressure (DP) Rating

What it is:
Design Pressure (DP) is a structural rating that measures a window’s ability to withstand wind pressure without failing. It reflects the maximum wind load a window can handle before its structural integrity is compromised.

Why it matters in Florida:
Florida building codes, especially in coastal and hurricane zones, require windows to meet minimum DP ratings. A higher DP rating means better resistance to strong winds and pressure changes caused by storms.

What to look for:

DP 35 or higher is generally suitable for inland Florida homes.
DP 50+ is recommended for coastal or high-wind areas.

2. Impact Resistance Testing: Large & Small Missile Tests

What it is:
Impact windows are subjected to rigorous missile impact tests to simulate storm conditions. These tests are part of standards developed by the American Society for Testing and Materials (ASTM).

Large Missile Test (ASTM E1996 / E1886): Simulates debris like a 2x4 launched at high speed during a hurricane.
Small Missile Test: Simulates smaller objects like roof gravel or broken glass striking the window.

Pass criteria:
The window glass may crack, but it must remain intact within the frame and continue to protect the home’s interior from air and water infiltration.

3. Florida Product Approval & HVHZ Certification

Florida Product Approval:
All impact windows installed in Florida must have state approval and be listed in the Florida Building Commission (FBC) database.

HVHZ Rating:
HVHZ stands for High-Velocity Hurricane Zone, which includes Miami-Dade and Broward counties. Products rated for HVHZ meet the toughest standards in the nation.

Tip:
Even if you don’t live in an HVHZ area, choosing HVHZ-rated windows ensures maximum protection.

4. Energy Efficiency Ratings

In addition to storm protection, impact windows also affect energy usage.

U-Factor: Measures how well a window insulates. Lower values = better insulation.
Solar Heat Gain Coefficient (SHGC): Measures how much solar radiation passes through. Lower values = less heat buildup.
ENERGY STAR Certification: Verifies compliance with energy efficiency standards for your climate zone (Florida is in the Southern region).

5. Sound Transmission Class (STC)

While not part of hurricane testing, many Florida homeowners appreciate the noise-reducing benefits of impact glass.

STC Ratings:

25–30: Typical for standard windows
35–40+: Common for quality impact windows

If you live near a busy road, airport, or commercial area, higher STC ratings offer noticeable noise reduction.

Bottom Line: Choose Certified, Florida-Approved Windows

When shopping for impact windows in Florida, look for:

A DP rating that meets your area’s code
HVHZ or Miami-Dade approval for maximum protection
Compliance with ASTM impact standards
Strong energy efficiency metrics (U-Factor & SHGC)
Bonus features like soundproofing

Need help choosing? At Artisan Windows & Doors, we specialize in Florida-approved impact-rated windows from trusted brands like CWS/Pella Storm Strong. Our experts provide low-pressure consultations and handle everything from permitting to flawless installation with no repairs needed after.