The recent hot weather has led to a surge in calls to windscreen repair companies for replacement glass services, following glass expanding in the heat. When this is combined with air conditioning and pre-existing chips, it causes windscreens to crack. The difference in temperatures between the heat outside and the cold interior of your car can put pressure on the windscreen and cause pre-existing chips or cracks to grow larger and spread.
Direct sunlight is as damaging to glass as it is to humans. The heat itself will not cause cracks in your windscreen, however cooling the glass rapidly when it is heated is a direct cause of extensive cracking. The hot and cold temperatures cause the windscreen to expand and contract respectively, which weakens the structure of the glass, therefore making it more prone to damage.
The process begins when cars are parked in direct sunlight without any method of protection, for example a sunshade. The surging summer temperatures will heat the glass of the windscreen, causing the interior of the car to heat up also. It would then seem natural to blast the cold air conditioning at its maximum setting as you enter your car, however this could be detrimental. It is important to avoid a significant difference between the temperatures of the interior and exterior.
To prevent your windscreen from cracking, it is vital that you take care of the glass, primarily by parking in the shade and avoiding direct sunlight for long periods of time, or by purchasing a sunshade. On the other hand, if your windscreen has already been heated by the sun, do not try to cool your car by ramping up the cold air conditioning. Examine the glass frequently, as small chips can be very difficult to notice, yet can lead to large cracks. It is important to have these repaired as soon as possible in order to avoid them growing, and to avoid having to replace your windscreen.