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Hurricane Impact Window Ratings Explained: DP, ASTM E1996 & What US Buyers Must Check
Hurricane Impact Window Ratings Explained: DP, ASTM E1996 & What US Buyers Must Check
If you are specifying windows for a project in Florida, Texas, or any coastal region, the words “impact rated” get thrown around constantly — but the actual ratings behind them are what determine whether your windows pass inspection. This guide explains the four ratings that matter and how to read them on a product label.
Why Impact Ratings Exist
Hurricane-rated windows do two jobs that ordinary windows cannot:
- Resist wind pressure — staying in the frame under sustained hurricane-force wind loads.
- Resist flying debris — surviving impacts from wind-borne objects (roof tiles, branches, gravel) without shattering.
A window must pass both tests to be legally installed in High-Velocity Hurricane Zones (HVHZ) and many other coastal jurisdictions.
1. Design Pressure (DP) Rating
The DP rating measures how much wind pressure a window can withstand, expressed in pounds per square inch (psf).
| DP Rating | Wind Speed (approx.) | Typical Use |
|---|---|---|
| DP 30 | ~110 mph | Inland residential |
| DP 40 | ~130 mph | Coastal residential |
| DP 50 | ~150 mph | Coastal / near-shore |
| DP 60+ | 160+ mph | HVHZ / high-rise exposed |
Key point: DP ratings are per size. A window rated DP 50 at 3’×5′ may only be DP 40 at 6’×8′. Always check the rating for your specific unit size, not the product line.
2. ASTM E1996 and E1886 — The Impact Tests
These two ASTM standards are the industry benchmarks:
- ASTM E1886 — the test method: a large missile (9 lb 2×4 timber) or small missile (2g steel balls) is fired at the window.
- ASTM E1996 — the performance standard: defines which missile and speed applies based on building height and location.
Missile levels at a glance:
| Missile Level | Projectile | Speed |
|---|---|---|
| Missile D | 9 lb 2×4 timber | 50 ft/s |
| Missile E | 9 lb 2×4 timber | 80 ft/s (HVHZ) |
| Missile A/B/C | Small (steel balls/gravel) | Varies |
After impact, the window must also pass cyclic pressure testing — thousands of pressure cycles without failure.
3. Miami-Dade NOA (Notice of Acceptance)
If your project is in Miami-Dade County, you need a NOA — the strictest window approval in the US. It confirms the product passed Miami-Dade’s own testing protocol, which exceeds ASTM minimums.
Miami-Dade also requires Product Control — each unit is labeled and traceable to the approved design.
4. Florida Product Approval (FL#)
Outside Miami-Dade but still in Florida, products need a Florida Product Approval number (FL#), issued by the Florida Building Commission. It covers the whole state and is often accepted in other Gulf states.
How to Read a Product Label
A compliant impact window label typically shows:
Manufacturer: [Name]Product Approval: FL# ______ / Miami-Dade NOA ______DP Rating: ______ psf (at size __ x __)Impact Rating: ASTM E1996 Missile EGlass: Laminated, [thickness]
If any of these fields are missing, the window is not documented for HVHZ use — and your inspection will fail.
Common Mistakes Buyers Make
- Buying on “impact rated” marketing claims without checking the approval number.
- Assuming one approval covers all sizes — approvals are size-specific.
- Mixing frame and glass approvals — the assembly, not just the glass, must be tested.
- Ignoring installation requirements — a rated window installed incorrectly still fails inspection.
FAQ
Does a DP rating alone mean the window is hurricane-proof?
No. DP covers wind pressure; you also need the ASTM E1996 impact rating and, in Florida, a state approval number.
Is Miami-Dade NOA required everywhere in Florida?
Only in Miami-Dade and Broward counties (HVHZ). The rest of Florida requires a Florida Product Approval (FL#).
Can imported aluminum windows get these approvals?
Yes — many overseas manufacturers hold FL# and NOA approvals. Always request the actual approval numbers and verify them in the Florida Building Commission database.
How do I verify an approval number is real?
Search the Florida Product Approval database (floridabuilding.org) or the Miami-Dade NOA portal with the number the supplier provides.
Sourcing Impact-Rated Aluminum Windows
If you are sourcing hurricane-rated aluminum windows for a US project, the supplier must provide:
- Valid FL# and/or Miami-Dade NOA numbers
- Size-specific DP ratings
- ASTM E1996 test reports
- Installation instructions matching your project conditions
KINGSHIELD supplies custom aluminum window systems for coastal US projects. Our manufacturing partners hold the required impact and product approvals, and full compliance documentation is provided with every order. Request a project quote →
