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Depending on the make and model, a windshield provides anywhere from 18 to 20 percent of the structural integrity of the vehicle. Passenger-side air bags rely on the windshield for support. If the windshield pops out during an accident the air bag will inflate out onto the hood of the car and become totally ineffective. That's just one more reason why it is important to have the windshield installed properly. The air bag inflates with such power that if the windshield hasn't been installed properly it can push the windshield right off the car. Also the structural support the windshield provides could prevent the roof from caving in on the passengers during an accident. A cave-in could inhibit any help, i.e. firefighters, from getting a passenger free from the vehicle.

Close to a million windshields are replaced each year in Canada. Thousands of those are installed improperly. A windshield is not difficult to install. There are steps which should be followed to make sure it is done right: the old adhesive has to be taken off; primers need to go on the body and on the glass; then the adhesive, urethane, is applied; and the windshield is put in place and left to sit so the urethane can cure. Curing time is one of the major problems with improper installations. Many installers don't let cars sit long enough to make sure they're safe to drive away. If it is not properly cured the urethane will be wet in the centre. This means weak points and the windshield will let go at its weakest point. Urethanes need up to six hours to cure safely. For maximum protection, to prevent roof crush, urethane has to cure for 24 hours, a lot longer than that in the winter. But for most shop owners time means money and annoyed customers.

There are government standards which govern the installation of windshields when a vehicle is being manufactured but these regulations do not legally apply to replacement windshields or after-market installations. The goal of these standards is to reduce crash injuries and fatalities by making sure as much of the windshield stays attached to the car as possible. Body shops and glass shops can be, and have been, held liable when they don't follow the vehicle manufacturers replacement recommendations.

Some shops don't even use urethane. To cut corners and save money they use things like silicon, bathtub caulking, and various types of adhesives that we don't even recognize to hold the windshields in place. The most common is Butyl. Butyl was used in the early 1970's but it is only a sealant not an adhesive and it never cures. Butyl is half the cost of urethane. But with Butyl there is no strength, it just pulls apart.

There are no government regulations which require an autoglass installer be certified or trained. To combat lack of training the National Glass Association in the United States established a certification program. Also, the glass division of the Ford Motor Company, called Carlite, holds one week installation schools throughout the year which are available free to anyone working within the industry.

So if you have a windshield that needs to be replaced, try to get it replaced the same way the car-maker installed it.

• Ask the shop if they follow the car-maker's specifications.
• Make sure they use urethane.
• If they keep the car for only a short time, ask questions.
• Find out what the proper cure time is for the adhesive they use. Remember it takes 24 hours - longer in winter - to reach a full cure.
• If the shop tells you they use Butyl, take your car elsewhere.