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Why You Need To Waterproof Your Hurricane Impact Windows

You’ve got hurricane impact windows, so you are fully protected from water leakage during a hurricane, right?

Not exactly.

Any kind of window, whether they are graded as a hurricane impact window or not, are not designed to be waterproof, but to be water-resistant. This is true even if they 
are installed one hundred percent correctly.

Most windows used in residential and commercial buildings are windows with moving parts that allow you to slide or swing them open them. Due to function and design, they cannot be fully sealed and still be operable. Functional windows have weather-strips and gaskets to seal the moving parts, but these are water-resistant, not waterproof. Some water will pass through the gaskets and weather-strips and enter the frame. The design of the frame allows the water to drain back to the outside of the building. With this in mind, it easy to see why hurricane impact windows can’t be waterproof. Hurricane impact windows, while stronger and more water resistant than ordinary windows, will still let wind driven rain intrude.

Resistance to water leakage is one of the performance standards hurricane windows are tested for to ensure they meet national standard requirements. Water is sprayed on the outside of the window as wind pressure is applied. This replicates the events of a hurricane where there is hurricane-force wind and rain. It is not so much the volume of rain that is applied, but rather the amount of wind pressure the window can withstand without leaking.

The amount of wind pressure used during testing is 15% of the wind load resistance the product is certified for. For example, a hurricane impact window with a wind load of 50 pounds per square foot (p.s.f.) will be tested to see if it can resist water leakage at 7.5 p.s.f. To put this in perspective, a window of 50 p.s.f. will only resist water at wind speeds up to 55 mph. What this means is that this window will likely leak at wind speeds higher than 55 mph!

In preparing your home for hurricane protection, you should take the necessary precautions to prevent water damage. There are 5 key things you can do to prepare your home as if you expect your windows to leak:

  1. Choose hurricane window products with the highest design pressure rating to make your windows as water-resistant as possible.
  2. Seal gaps in cracks or voids (caused by weather or aging) under windowsills with caulk.
  3. Install flashing (a thin metal strip) around your windows and doors to prevent water intrusion in spaces where two different building surfaces meet.
  4. Install shutters over the windows to help to keep water off the windows and window frames.
  5. Apply sealant to the joints of the windows. However, it should be noted the windows would not be able to open from the inside while the sealant is in place.

The bottom line is that there is no such thing as a waterproof window in hurricane-force winds unless you want to install portholes.