What is the Design Pressure Rating of a Window and Why is it Important?

When you buy windows, you look at a number of different factors in order to determine which is the best window possible for your home. In addition to the color and style, one element that’s important to think about is the design pressure ratings of windows.

design pressure ratings

You don’t want to make an essential purchase for your home that isn’t durable. Read on to learn all about design pressure ratings and why they’re so important.

What is Design Pressure Rating?

The design pressure rating is a way to measure the impact that a window is able to tolerate. This impact, or the load, can come from a number of sources, primarily from wind, snow, rain and other environmental factors.

The load is measured for the end-use of the window. In other words, the rating is for the load that the window can carry once it’s installed properly in the home, not just for the window sitting on the store’s shelf.

The methods that they use to come up with a design pressure rating are clear, research-backed ways. It’s not just a number randomly given in order to boost a window’s sales. The number has been come up with by a lab that has been vetted and declared fit to give ratings.

Organizations such as the American Architectural Manufacturers Association, the National Fenestration Rating Council, and the Window and Door Manufacturers Association all make sure that the number that testers come up with for the windows’ design pressure rating is scientifically determined.

Different labs will put the window through a series of tests. The tests seek to determine how many pounds of pressure a window can take per square foot. One test will hook up the window to a wooden frame, which is then attached to a wall that has been designed for this specific test.

The researchers then lower the pressure in the window, which increases the outside pressure. They do this until the window shatters, and record their findings. The pressure tested must be at least 1.5 times what the design pressure is for at least 10 seconds.

Your Home’s Required Design Pressure

design pressure of windows

Rather than just buying the prettiest window or the cheapest option out there, you want to be sure you meet the design pressure rating for your area in order to avoid potential problems. Your home could be flooded or destroyed during a storm if your windows aren’t strong enough.

Also, windows that are too weak could pose a safety risk. Sometimes strong, sturdy windows that can withstand pressure are enough to save your home from major destruction during a storm.

If your windows aren’t within the design pressure minimum and an event occurs that threatens those windows, your homeowners’ insurance may not cover the destruction since your house wasn’t within legal standards.

Every area will have a different minimum design pressure rating that must be met in order to meet the legal building requirements. For example, the geographic location of the home plays a major role.

Different Design Pressures For Different Areas

A house that’s in a hurricane zone or in an area with a lot of rainfall may have a design pressure rating requirement that’s much higher than a house in an area with relatively calm weather throughout the seasons.

Another factor that is considered is the height of your home. The height, depth and length of a building will play a role in how much pressure can be applied to that window, therefore impacting the design pressure rating. Where the window is to be placed is also essential to considering the DP needed. A window that’s in a lower area on a home may need a different DP than a window in a higher up area.

To find out your area’s minimum DP rating, go to your municipality’s website or building to find out if they have paperwork for you to read. Usually, there are charts and literature that lists the window requirements.

Another place to seek help is to ask a company that specializes in professional window installation. They’ll be able to help you figure out the required DP rating.

Not the Same as Energy Efficiency

Keep in mind that the design pressure rating isn’t the same as how energy-efficient your window is. The design pressure rating specifically addresses how strong your window is and how well it’ll hold up to the need to bear weight.

This could be different from a window that’s built to lower your energy bills by keeping out unwanted hot or cold air. A window with an excellent design pressure rating may very well also provide energy-efficiency, but the two don’t necessarily go hand in hand.

For example, some storm windows are a great idea for people who want energy-efficient options. A storm window may have a low-e coating, which means that a coating has been applied in order to lower the emissivity of the glass. This coating will also help to lower the amount of heat that can escape through the window.

If you live in an area with warm weather, solar control storm windows can be a great option. One measure for energy efficiency that, as you’ll see, is quite different from the design pressure rating is the U-factor. This measures how much non-solar heat flow passes through a window. You want a low U-factor in order to get the most energy efficient window.

However, a window that has a low U-factor and that has been labeled energy efficient is not necessarily strong. If you want a window that meets the design pressure rating for your area and that is energy efficient, you need to consider all of the measures possible.

It’s Important to Understand Design Pressure Ratings

The design pressure rating may seem like a concept that’s difficult to understand, but it’s truly a subject every homeowner should know a bit about. Each area of the country will have a different design pressure rating, since numerous factors go into it.

One major element to consider is your area’s weather. If you live in a coastal area where your home faces bad storms and strong winds, your windows may need to be a bit stronger than someone in an area with milder weather. Talk to people who work in your municipality to find out what kind of windows you need to buy so that you can avoid a disaster.

For homeowners in Chicago, the choice is easy. Feldco has been serving the area for over 40 years with the best window replacement available. Our windows are specifically designed for the weather in Chicago.

Start your window replacement project today with a free quote online and join the over 350,000 homeowners who trust Feldco.

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