DP Rating Of Windows

DP rating of windows - the term, DP, is used to describe the design pressure of a particular window. This is a key term when it comes to judging the overall strength of the window. In particular, this is an important metric as it relates to hurricane windows. The higher the DP, the more resistant the window to force or wind that occurs during a severe storm or hurricane. Obviously, this is important in coastal regions that are subject to these severe weather events. Let’s explore this interesting topics in more detail.

Written by: Dane, Site Editor
Experience: 40+ years in window installation and replacement
Editorial Review: Replacement Windows Reviews Team
Original Publish Date - October 17, 2025
Page Last Update: June 24, 2026

Basics Behind Design Pressure

Design Pressure or DP measures how many pounds per square foot a window can handle or withstand. During the process of getting a window certified by the AAMA as an impact window, the testing crew puts the window through a series of tests that covers air, water, and structural integrity. Obviously, DP rating of window focuses on air.

Related Topics: Hurricane Impact Windows Cost Calculator

Design Pressure Testing

So, to test for design pressure, the testing crew starts with a low level of pressure against the unit and continues to increase that pressure until the window fails (damaged). Specifically, the pressure must reach 1.5x the DP for 10 seconds and not cause permanent damage for the unit to achieve a certain rating. So, for instance, for a window to achieve a design pressure of 30, it must withstand 45 pounds per square foot (1.5x) for 10 seconds.

DP And Where You Live

Most non coastal areas require a design pressure rating of 30. However, there are a number of factors that influence DP requirements. These include the location, height of the building, window location on building.

Most coastal regions or those regions that are subject to severe storms require a DP rating of at least 55. If you are unclear on what the DP rating of window is on your hometown, call up a local window company and ask. They ought to have this information on lock as they install windows on a weekly or daily basis.

Sample DP Ratings Of Windows

FiberFrame Windows - 30 Design Pressure

ProVia Endure Series - 50 dp rating of window

Ellison 1050 Series - 50 Design Pressure

Mercury Excelum Series - 50 DP Rating

Simonton Stormbreaker Plus - 65 DP Rating

CWS Windpact - 65 design pressure

ViWinTech Shoreline Impact Window - 70 DP

PGT WinGuard 70 DP for windows

Hurricane Wind Scale

Here are the basics categories and accompanying wind speeds to the Simpson hurricane window scale.

Here's a helpful rule of thumb - every 10 points in the DP (Design Pressure) rating is roughly one hurricane category. So, for example, for a window with a DP rating of 30, it can withstand the sustained winds of a Category 3 hurricane, while a DP rating of 40 aligns with the conditions of a Category 4 storm, and so on.

Additionally, it’s important to note that these ratings are based on sustained wind speeds only. They do not account for short-term wind gusts, flying debris, or tornado activity that often occurs during severe weather systems.

Also, while Category 5 hurricanes begin at 157 miles an hour, recent storms have brought sustained winds exceeding 200 miles an hour. This has led some experts to suggest the need for a new classification — like a Category 6 — to more accurately reflect the increasing severity of these extreme weather events and storms.

Related Topic: Windows Terminology

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