http://brewwiki.win/wiki/Post:Fitting_a_Cat_Flap
A door made of upvc that has a cat flaps can help reduce draughts in your home. By keeping your pets warm and out of cold air, you can reduce heating costs. It is possible to fit cat flaps into the upvc panels as well as double glazing glass sealed units, however it is more difficult than for doors made of timber. This is due to the fact that there are different thicknesses of Upvc. Benefits A cat flap placed on your door will allow you to keep your pet inside or out of the house, while let other people in. It also helps keep out stray c