I had one of these valves in another location and really liked it. In the winter, we vent the dryer in the house to take advantage of the heat, in the summer we vent the dryer to the outdoors. I caution to use only on electric dryers because gas dryers will put carbon Monoxide in the house and could cause great health harm to the residents. I gave it 4stars because it is not completely sealed due to light construction but adequate.
should have better stronger seams and the screen should snap or screw on does not want to stay on the one I got and should have a flat back so if you want to drill a hole to mount it to the wall you can and should have a seal around the flapper to help keep the air from leaking out on the up side it does work and for the cash its worth the money and in the winter time I can see this keeping a small room a tad wormer so you do not need to run a heater as much win drying your cloths to keep a room worm
This helps recover heat loss from using your dryer in the winter. It also helps to bring humidity into your home as well. It does have a lot of excess plastic on it from the mold used to make it. If you remove this excess, be careful as not to take to much off where the filter screen goes as it will leave it hard to attach.