A Better Vent Cap for Range Hoods, etc?
I have a range hood to install and a direct 3 1/4″ X 10″ wall vent cap to use with it. As it’s going to hit -26 Celsius here in Alberta tonight, I think I’ll wait, but that also has me thinking I don’t want this big, uninsulated hole in my wall. It’s simply a galvanized steel channel with a spring loaded cap at the end — I can even see daylight at the edges of the flapper.
Is there a better way to deal with this thermal weak point in the building envelope?
I know Broan has a nice system called the Eco-Vent for dryer vents (an insulated vent cap with a styrofoam ball that blows out of the way when needed), but that’s only a 4″ system, I would need 7″ if using my round top vent option. The equivalent for range hoods would be fantastic (although kitchen grease might muck it up in the long run.)
Thanks,
Geoff
Replies
There are motorized, in-line dampers that would seal the vent pipe better than the flapper on the end. Depending on the power of the blower, you might have to wire in a time-delay relay to allow the damper to swing open fully before the blower motor kicks in.
Thanks TJK, I had googled the 'net a bit before posting, but was looking for "vent caps" etc... I've found a few now looking for "motorized dampers" but generally a bit pricey and oversized. I'll hunt on. Good point about the delay. This is only a 160 CFM fan, so probably okay in this case.
Any low-tech alternatives are still welcome! I was going to tinker with backing the flapper with thin rigid foam, but of course it requires room to pivot so I'd never get a perfect fit.
For your application here is an interesting damper with no moving parts:http://www.rewci.com/noname6.htmlIt has a fabric sleeve that collapses when the airflow reverses.
The fabric sleeve is an interesting concept. How do you know it collapses? Thon
Our Jenn-Air cooktop has a downdraft vent and we installed one of the sleve dampers because on windy days reverse air would always blow though the pipe. It's not as tight as a mechanical damper, but it works well enough in our system.
I know there are through-the-wall exhaust fans with tight seal insulated cover, I don't know if you can just buy the cover and adapt it to the hood vent though.
It is decidedly low-tech, but you could build a foam box/cover that fits over the interior end. Something that attaches up under the hood itself.
Thanks for the input. After searching the 'net for backdraft dampers and so on, I'm suprised there aren't better solutions out there. I'd hate to build a good, tight eco-home and have over 30 square inches of a piece of 28 g. galvanized steel between my kitchen and the great outdoors. That dryer "Eco-vent" sounds promising, maybe Broan will create an equivalent for ranges (I started thinking maybe I could Y off to a pair of those, but even that isn't enough capacity.)
The inline motorized option is pretty good. Still a thermal weak point, but seals better than the flapper unit I picked up. Pricey though for a humble home like mine.
Other interesting things I found in my quest: exterior blowers are pretty nice. The noisy work gets done outside. And some deliver CFM that will suck your visitors' toupees off and toss them in your hedges.
And a thermal break in the actual ducting is recommended in very cold climes, e.g. a piece of rubber ducting in the middle of the run to break up the cold transfer from the steel. Keeps the range hood itself from getting cold.
Geoff
Commercial venting often has the blower outside at the end of the duct run. Perhaps that setup would provide more of a block againest cold? And you could put the thermal break right there at the connection between the duct and the blower.Of course, ugly is in the eye of the viewer.
I've had my range fan out of the wall, and the exterior opening insulated and sided over for about 2 years now, while I think about what to do about the issue you're struggling with. Obviously I'm not thinking too hard--or too much. <G> Let us know if you find something.Thon