Clear Protection: The Value of High-Impact Windows

by Kathy Danforth / Published June 2015

Windows and glass doors—those lovely holes in the wall—have long been the weakest point in keeping the elements outside where they belong. Fortunately, the ability to enjoy views and natural light without compromising the barrier’s resistance to wind, temperature, and water has improved greatly with the development of high-impact glass.

“Before 1970, there was very little control over what type of products were used in residential and commercial construction,” says George Hanus, Marketing Manager with WinDoor, Incorporated. “Consequently, there were a great variety of products. With no particular wind, water, or design pressure codes to determine what products should be used, the products were made just to ‘fill the opening.’ These were often the lightest glass thickness, with minimal concern for water and air infiltration.”

Hanus estimates that 35–40 percent of homes in Florida still have these older windows and sliding glass doors, as well as about 25–30 percent of the condominiums built before 1970. “Cost was the driving factor at that time, without consideration for longevity or protection,” he observes.

“After 1970, there were some modifications in the standards, which improved the window and sliding glass door construction industry,” Hanus relates. “Tempered glass was specified for sliding glass doors, but windows and framing materials remained the same.” Standards continued to tighten as AAMA (American Architectural Manufacturers Association) specifications were incorporated into building codes. Hanus remarks, “Still, those standards were far below what is required today. The number of homes that are not up to current standards, from both before and after 1970, is around 55–60 percent.”

“Hurricane Andrew, in 1992, caused such devastation that many different building code changes resulted from that storm. Not only were window and door strengths specified, but also how buildings are constructed, roof supports, and things of that nature,” Hanus explains.

“After Hurricane Andrew, the requirements for window and sliding glass door construction were upgraded to the current impact codes for new and replacement windows and sliding glass doors in the ‘Impact Zones.’ These new codes also included new wind zone codes that required testing to determine if these products would withstand hurricane wind and water loads. Today’s building requirements are guided by the Florida Building Code, which specifies which areas of the state are in an Impact Zone (see map below).

“There are very specific guidelines as to what minimal standards must be met for wind, water, and design pressures for each zone,” Hanus states. “All products in Florida have to follow the installation protocol, which is determined by the state. If someone is using a reputable dealer, an inspector will check for the number of fasteners specified for each side to ensure the product will perform as required. If someone just shows up to install a window with no inspection, that’s what causes problems. You can build the best product, but if it’s installed incorrectly, we’re all in trouble.”

Requirements are also in place for small and large missile protection, with the type of protection required determined by the height of the building. “Up to 30 feet, or the first three floors, glass must meet large missile impact requirements,” according to Hanus. “However, in some cases, buildings may take that protection all the way up for the protection of the residents. If there are two buildings side by side, large debris could fly off one building into the other at a higher elevation than if there was not a taller structure nearby.”

Stringent testing is performed to ensure that glass will not be dislodged and water will not penetrate at the wind rating for the glass. A 2-in. x 4-in. x 8-ft. wood stud is fired at the window or door at 35 miles per hour and must not cause penetration of the glass. “After the window or sliding glass door is hit with this projectile, then the rating (wind load) that the manufacturer is trying to attain is applied to the product. Nine thousand cycles of varying pressure are applied alternately to the interior and exterior of the product to simulate the varying pressure in a hurricane,” Hanus explains. “There must be no failure of the glass or frame.”

Testing for small missile impact resistance is similar, except the projectile is a ball bearing. After shooting the glass three times at 35 mph, the glass is then subjected to 9,000 cycles of pressure applied to each side of the glass. “Some zones in the south part of the state have windows rated for 150 mph wind,” comments Hanus.

While protection from hurricanes is the high-profile motivation for high impact windows and doors, other benefits can be financially and environmentally significant. “Thermally broken windows and doors will be the future to solve the energy codes that will be faced very soon,” says Hanus. A thermally broken window has a thin layer of a polyurethane insulating polymer that stops the transmission of heat (either direction) between the inside and outside of the window frame. This thermal barrier conducts up to 1,000 times less heat than the solid aluminum, greatly improving insulation and energy efficiency of the building. “It also has the side effect of making the windows more soundproof by dampening vibrations between the inner and outer frame,” Hanus points out. “The thermal barrier does not weaken or become brittle, and outside laboratories test to ensure that the extruded material will not come apart.”

Hanus shares, “In areas up north, new buildings and retrofits are required to use windows with a thermal break. Those energy codes are starting to creep down here to Florida, so we are being proactive and designing products that will meet the energy codes of the future. If someone is replacing windows, why spend money on straight aluminum when five years down the road, when you are trying to sell the home, it will not be up to the current code?”

Thermal break windows and doors can result in immediate energy savings, as can low-e (low thermal emissivity) glass. “The newer types of windows and sliding glass doors that use low-e glass typically reduce the electrical costs from 15–30 percent, depending on how the resident sets the thermostat and what types of products were replaced,” observes Hanus.

“By upgrading windows and doors in a condominium, there is the possibility that the insurance company will give a price discount for the whole building because now the entire envelope is protected by impact glass,” says Hanus. “Going from non-impact to impact protection will reduce the insurance costs from 15–20 percent in most cases, and even more in coastal areas. Before the housing market collapse, insurance companies were hammering buildings to take the necessary steps to protect their structure. When the economy crashed, they let up, but, at that time, some buildings were not going to have their insurance renewed if windows were not protective, and that trend may resume.”

Hanus advises looking for the best value rather than strictly the best price; while the initial project cost may vary by only 5–15 percent, the value of the finished product may vary by 50 percent or more. The quality of the products and the reputation of the installation company are determining factors, since the product is only as good as the installation. For warranties to have value, the manufacturer and installer should be stable companies with the likelihood of still being in business should the association need them.

Because of the multiple benefits, impact windows and doors catch the eye of homebuyers. “New windows and sliding glass doors added to a condominium or residence typically increase the home’s value by twice the cost of the investment,” reports Hanus. With their resistance to wind, water, heat, insurance increases, and the occasional thief, a community’s view toward impact windows may come to be as pleasant as the view through them.