Guide To Window DP Ratings

Our guide to window design pressure explores the various aspects behind this important replacement window ratings component. DP stands for design pressure and is a measure of the amount of simulated wind or pressure can be applied to a window before the structural integrity is compromised.

A typical replacement window has a DP rating of between 25 to 35. Replacement windows that are made to withstand hurricanes will have a DP rating of 45 or higher.

Basics Behind Design Pressure

DP rating is, in general, an indication of the overall strength of a replacement or new construction window. A DP30 rating means that the window is tested each way for 10 seconds for structual integrity at a maximum speed of 130 miles per hour (which is the top wind speed of a category 3 hurricane). A DP40 rating means that the window is tested for 10 seconds for structural integrity at a maximum speed of 155 miles per hour (category 4 hurricane). A DP50 rating means that is windo is tested each way for 10 seconds for structural integrity at a maximum speed of 173 miles per hour (category 5 hurricane). Most residential windows are fine with the DP rating of 30. homes that are located in hurricane or severe storm prone areas typically require a higher DP rating.

Achieving DP Rating

There are a number of steps that a window manufacturer can take in order to achieve a higher DP rating. The first, and most important, is to upgrade from a low-e to a laminated glass. Laminated glass is much stronger than low E glass and does not shatter if struck by a hard object (as might happen during a hurricane). Instead, the laminated glass may crack, but will remain intact in the frame.

Other steps include better weatherstripping, seals and components that all work to create a stronger and more durable window that can stand up to storms and even hurricane type conditions.





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