Dog and Cat Pet Doors are items you should really think about before purchasing. No matter whether the item will be used in your house on one of your doors, windows, etc. or whether it will be used for one of your pets in their outside house, you want it to last a long time and be impervious to weather......also sometimes to varmints. It should be an extremely weather and wind resistant door, etc.
Below, you will see pictures of an actual test made by a blower and a windmeter.
I am the one who conducted the test, not the manufacturers. So, I can honestly say that I stand by what the manufacturers say.
If it is to be used IN your house, it should be of the highest quality in order to save you on power bills. What you may save buying a "cheap" pet door, you will lose many times down the road because of poor insulation, cheap materials, or inadequate closure. You also want a door that will be longlasting as some of you will not be able to install your own due to lack of skills and equipment. Therefore, you want the one you pay to install to last forever, LOL!