DP Rating Of Windows

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Design Pressure 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.

Dane - Site Editor - Page Last Updated: January 9, 2025

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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.

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

FiberFrame Windows - 30 dp
ProVia Endure Series - 50 dp rating of window
CWS Windpact - 65 design pressure
PGT WinGuard
Simonton Stormbreaker Plus - 65 DP Rating

CWS vs PGT Windows

Dane, I was curious what you thought of the CWS Windpact window? I have a bid on 20 impact windows for $29K installed and didn’t know if this was a good price or not. Also, what do you think of this window in comparison to say a PGT WinGuard. About the same price for this one, a couple of hundred dollars more. They kept mentioning design pressure ratings and how impressive theirs was. Both were 65, which made me laugh, because they were exactly the same. LOL. Anyways, love to get your take. Barbara

Barbara - Homeowner - from 2025

[Site Editor's Answer]

Barbara, the CWS Windpact is an excellent impact windows for and a 65 design pressure is impressive. The PGT WinGuard Is also very good and the 65 DP rating of windows is equally impressive. So their bragging was somewhat justified. Honestly, I would put these two windows on par with one another. When coupled with professional installation, these will serve you well. Therefore, for me, the answer here is to choose the installation company with the best online reviews. This is going to make the much bigger difference over which of these two excellent hurricane impact windows you have installed.

Dane - Site Editor - from 2025

Related Topic: Windows Terminology

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