Speedi-Products AC-BD 08 8-Inch Diameter Galvanized Back Draft Prevention Damper

Gravity close doors, no springs. Fiber reinforced tape holds the doors on, no metal hindge. Seems to do the job just fine.

Great concept for closing the damper. The hinge is some type of fiber reinforced fabric or plastic and uses gravity to close the damper. I used this damper in a horizontal position and you have to be careful which direction you install the damper. The hinge has to be vertical and the slant of the hinge has to be such that that gravity will pull the damper shut. If you are installing the damper in a vertical orientation, it will only work for exhaust systems, unless the outside intake is below the damper for intake applications. My only complaint is they should have included directions on how to install or better diagrams on the damper itself.

I had a specific non-typical project I experimented with this damper for--an air exchange system for a low thermal mass attached sunspace. This particular damper didn't work for my application. On windy days the sunspace internal pressure was easily enough to open the damper and keep it open, forcing cold air from the sunspace into my home. In the end I ended up buying an electric/automated damper which has worked great:http://www.amazon.com/review/R1WBBYKN6SD16H?_encoding=UTF8&ASIN=B0015S4LQU&cdMSG=addedToThread&cdPage=&channel=detail-glance&newContentID=Mx1P7WQ89ITNBE7&newContentNum=1&nodeID=16310091&store=industrial#CustomerDiscussionsNRPBThis damper probably works well for most applications, but not for mine. But thought I would post this for the few people who might be doing something similar to my project.

i have this installed on the output of my whole house dehumidifier. per the installation instructions i needed this when ducting the unit into the HVAC supply ducts. mine arrived quickly and in perfect condition. the flaps seal quickly, and make a fairly nice seal on the gasket material. "some" air of course does get through, mostly around the hinge joint, but this thing easily blocks 99% of the air flow.

would be nice if it were crimped on both ends. had to use gorilla tape instead of clamps for one side. other than that it works just fine.

This is a good product, it's very funtional. double damper, I take one off due to flow decrease too much.

When we recently bought a new house (9yrs old actually) my wife kept saying she felt a breeze under the range hood when she cooked. I took apart the vent fan and lo and behold there was no backdraft damper of any kind installed. I could not believe it. This BD damper fit like a glove and only took 5 minutes to install. No more threat of a dead bird suddenly dropping in to the soup.

Not so sturdy, but does the job.