Back to Blogs
What Is a DP Rating for Windows and Doors?
What Is a DP Rating for Windows and Doors?
If you’ve received a quote for replacement or hurricane impact windows, you probably noticed something called a DP rating listed on the proposal or window label.
Most homeowners aren’t told what it actually means - but it’s one of the most important factors in protecting your home during severe weather.
This guide explains DP ratings in simple terms and why they matter when choosing new windows and doors.
What Does DP Stand For?
DP stands for Design Pressure.
Design Pressure is a structural performance rating that measures how much wind force a window or door can safely withstand once installed in your home.
The rating is defined by major industry standards organizations, including:
AAMA (American Architectural Manufacturers Association)
WDMA (Window & Door Manufacturers Association)
NAFS (North American Fenestration Standard)
DP is measured in pounds per square foot (psf) of pressure applied to the product.
In simple terms:
The DP rating tells you how strong the window or door is.
Why DP Ratings Matter
During a severe storm or hurricane, wind doesn’t just blow against your house - it creates powerful pressure changes. Air pushes, pulls, and flexes the structure.
When a window fails, outside pressure rushes into the home. This is what can lead to:
Roof Damage
Water Intrusion
Interior Destruction
Structural Collapse
That’s why building codes place strict requirements on window performance.
High-performance systems such as WW Impact Series windows and doors are engineered specifically to resist both wind pressure and flying debris, helping maintain the protective envelope of the home.
What Determines the DP Rating Your Home Needs?
Typical Florida DP Requirements
Because Florida experiences hurricane-force winds, its building codes are among the strictest in the country.
General guidelines:
Inland Areas
Typically DP 35–50
Coastal Areas
Usually DP 50–70+
High Velocity Hurricane Zone (Miami-Dade & Broward)
Often DP 70–100+
Impact-rated products, including WW Impact Series windows and doors, are manufactured and tested to meet these higher performance levels when properly sized and installed.
The 25% Window Replacement Rule
Florida Building Code includes a regulation many homeowners learn only after starting a renovation.
If you replace 25% or more of your home’s total window area within a 12-month period, the new windows must meet current building code requirements.
This means:
Required DP rating
Impact resistance
Updated installation standards
Your contractor or building department can help determine if your project triggers this rule.
Every certified window or door includes a permanent label showing:
manufacturer
model
size approval
certification standard
DP rating
You can also confirm requirements with your local building department, which uses wind load charts specific to your address.
Frequently Asked Questions
-
DP ratings are one of those things homeowners hear from sales reps but rarely actually understand… yet it’s literally the number that determines whether a window protects their home during a hurricane or fails.
-
Florida Building Code is based on wind zones, not temperature.
Your required DP rating depends on:- Distance from the coast
- Home height
- Exposure (open water vs neighborhood)
- Opening size (bigger windows require higher DP)
A window can be:
- Impact glass
- Laminated
- Hurricane labeled
…and still fail inspection if the DP rating is too low.
-
DP ratings are verified through laboratory testing - not estimates.
Here’s how it works:
The window or door is installed into a reinforced test wall.
A pressure chamber simulates hurricane wind forces.
Air pressure is manipulated to stress the unit.
The product is pushed to extreme limits.
To pass certification, the window must withstand 150% of its rated DP pressure for 10 seconds without permanent damage.
Example:
A DP 50 window must survive 75 psf of pressure.Only after successful testing does the product receive a certification label showing its DP rating.