This is why in very cold climates the main vent stack is often full-sized and a 4-inch-diameter pipe. The larger pipe size means that much more frost must form to choke off the air supply.

The standard size of a microwave exhaust vent opening is 10″ x 3 1/4″, but you’ll have to measure your old vent pipe diameter. LaurieJean’s was 7.5″ – a rather unusual size (usually ...

The Kozy Kollar is a heavy-duty rubber vent that allows a PVC pipe to go up through it. It will work on a 0 to 12-pitch roof, and it takes about an hour to install from start to finish.