The Importance of Understanding Your Home’s Window Design Pressure Ratings

04/14/2023

Why do they matter?

Design pressure (DP) ratings indicate the maximum amount of positive (pushing) and negative (pulling) pressure that your windows can withstand without breaking during events like hurricanes or tornadoes. Understanding the DP of your windows matters because it can help you evaluate the potential performance of your home in a high wind event. Knowing that your windows have a lower DP may also help make a case for investment in hurricane shutters or newer, impact-resistant windows.

Design Pressure (DP) rating on windows is different from impact-resistance ratings. DP only reflects wind pressure, not impacts from flying missiles or windborne debris that commonly occurs in high-wind events.

What do I need to know?

• Use products that are tested and approved using a standard established through a recognized product approval system or evaluation report.
• Refer to your local building department to identify appropriate DP Ratings. DP ratings and requirements vary by your wind zone location and even by the window location in the wall. For example, DP rating requirements in the middle of the wall may be lower as the pressure is lower there compared to windows located near the edges where wind pressure is greater.
• Avoid designs that include large spans of glass, windows with multiple panels, and double entry doors when constructing a new building in areas subject to high winds. Single door widths and windows should not exceed three feet.
• Correct window installation is essential for proper window performance. Choose the correct DP rating, add impact-resistance attributes, and follow manufacturer-provided instructions to ensure windows perform optimally in high winds.

Where do I start?

Replacing your windows

• Check with your local building department for information about the required DP for windows where you live.
• Follow manufacturer specifications when using or installing wind-resistant windows. Improper installation may cause a voided warranty or even product failure that presents a threat to life and property.
• Enhance your window performance by selecting windows rated for both wind pressure and impact resistance from flying debris.

More Resources:

• FLASH. Resilient Design Guide Wood Frame.
• FLASH. Resilient Design Guide Concrete.