Product review (5 stars): A worthwhile investment!
We purchased this product to cut down on the breeze that blew through a straight exhaust louvered vent whenever the wind blew.  Our laundry room was easily at least 10 cooler in the winter and the door had to be closed to keep the draft contained to that room.  The unit installed easily. The best way is to remove the vinyl siding to install the unit, then put the siding over it.  Due to the larger square cut originally made in the siding, we had to replace that piece of siding. We then painted the vent and surrounding caulking to match the siding. I noticed the following day that the laundry room was the same temperature as the rooms on that side of the house, no more walk-in cooler!  The vent works exactly as advertised.  The dryer stays warm after it shuts off and I expect that my drying cycles on cold days to be shorter given the fact that cold air isn't competing with the outside winds.  I have bragged about this device since no one at local hardware stores were familiar with it.  A worthwhile investment! I am considering buying another unit to replace my range hood vent since that is another source of cold air.