Dryer vents, bathroom fan vents, kitchen range hood vents, you know—those hoods on the outer walls of your house with the flapper that keep wind, rain, and critters out of your ductwork. Some are metal, but the majority of the smaller ones are made of plastic. UV rays from the sun will cause the plastic to break down over time. I always use and recommend a steel vent cover. The price of the part is higher, but it’s money well spent. When these fail, it often goes unnoticed. Have a look at yours regularly—you can almost always see all you need to know from the ground. And keep an ear out, as well: if something sounds amiss in the bathroom ceiling when the wind blows, the cover might be the cause.
The failure of this plastic cover was especially dramatic. Not only did the damper flap disappear, so has most of the hood.
I replaced with metal.
These hoods are readily available, and certainly DIY-able, provided you don’t mind ladders. I actually do mind them, so I’ll usually only service first floor vents. If you need a replacement, and have no desire to do so, give me a call (if it’s on the lower level :-).