According to the U.S. National Oceanic & Atmospheric Administration, winds more than 50 miles per hour are generally likely to cause window damage, mainly due to rocks, outdoor furniture, landscaping and other debris becoming airborne.
Is there such a thing as hurricane window film? Maybe you’ve seen advertisements touting these as a less costly replacement for storm windows or hurricane-resistant windows.
It is true that window tint films can make your glass shatter-resistant, and give you an additional element of safety. These same shatter resistant properties can help save your life in the event of a tornado or hurricane, preventing them from sending shards of glass flying through your home. But most window films will not bring existing windows up to hurricane code standards.
Following Hurricane Andrew, The Miami-Dade Building Code and Compliance Office instituted rigid standards and test protocols for impact protection in windows and doors. These standards are comprised of two impacts on windows by a nine-pound two-by-four traveling at 50 feet per second, followed by up to 9,000 cycles of positive and negative wind-loading. Windows passing the test can be expected to withstand winds up to 130 miles per hour. Code changes in other areas of Florida, Texas, and the Carolinas followed along the same lines.
Window films are designed to lessen the amount of solar generated thermal transmission through a window into your home’s interior. They do this either by increasing solar reflection or solar absorption through the glass, or both. The film’s tint and mechanical properties absorbs or reflects the sun’s heat energy, thereby reducing the thermal energy in the room.
In the event of high velocity winds, these window films may have important safety value. They can lessen risk of injuries from airborne pieces of broken glass, and have the potential to prevent debris and water ingress through the window depending on the storm’s severity. Effectiveness will also depend on the type of glass, framing system used in your windows.
However, window film is not considered to be hurricane protection, either by insurance companies or building codes. Consequently, a homeowner will receive no reduction in their insurance premiums. If you are looking for ways to save money on heating cost, reduce ultraviolet rays in the house or reduce risk of injuries associated with airborne glass, then window film is a good option.
What about hurricane protection, then? Of course they are better than no protection, but window films offer the least protection of your options. Specially designed hurricane impact resistant windows, accordian-folding hurricane shutters, plywood hurricane panels, corrugated metal roofing panels, roll-down metal shutters, all are far superior.
The one benefit hurricane window film offers is that the glass is held together after breakage. Quite often window frames are not properly fastened in the house or the glass is not fastened securely into the frame, thus no matter how efficient the film is, the glass comes loose from the window frame or window itself comes out of the wall.
Window film also has an advantage in price, generally being the least expensive of the options, and some protection is better than no protection, so it is not without value.
Hurricanes characteristically bring about failure to glass windows when an object hits them or when the outside air pressure suddenly drops radically below the air pressure level inside of the house. A difference of a couple of pounds per square inch induces around one ton of stress on the average size window.
These extreme pressure differentials are actually fairly well tolerated by glass, rather it is the materials of sills and retaining structures that fail. For the window to withstand hurricane force winds, the stress load must be transferred to the building structure itself, which is why specially designed hurricane resistant windows are so expensive- window frame reinforcement and anchoring system are required to meet the codes.