https://wizdomz.wiki/wiki/Fit_....a_Cat_Flap_in_a_UPVC
A door made of upvc that has a cat flap can help to reduce the amount of draughts that enter your home. You can save money by keeping your pet inside and the cold air outside. It is possible to put a cat flap into the upvc panels as well as double glazing glass sealed units, however it can be more difficult than with timber doors. This is because upvc comes in various thicknesses. Benefits Having a cat flap fitted to your door is a great method of keeping your pet in or out of the home while still allowing people to enter. I