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solarhotairpanels 11-09-13 05:41 PM

Inexpensive Backdraft Damper that actually works
6 Attachment(s)
I have tried the store bought metal butterfly backdraft dampers with the 4 hot air collectors I have plugged into my house.

None of them were stopping the cold air backdrafts that happen when the sun goes away.

After doing some digging, I ended up finding a different Mfg. backdraft damper on the web that I liked so decided to copy their design and see if I could get good results.

After some trial and error with different materials I finally nailed the problem.

I made a pdf file showing the build which is here for anyone interested.

A minimum of materials are needed to put these together..

Attachment 3615

Attachment 3614

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Attachment 3610

Exeric 11-09-13 07:15 PM

Good job! I'm already starting to think about this for the large renovation I'm doing. I'm just glad you posted this before I'd passed that construction point.
Big thanks.

solarhotairpanels 11-09-13 09:48 PM

You're very welcome Exeric,

What's cool about this type of damper is it can be customized on the fly as in sized to any duct size and configuration of ductwork.. or just used to stop drafts in certain areas of your home / shop etc.

round / square.. it doesn't matter as long as the material you use is long enough so after it collapses it just flops flat, sealing the opening.

The ones I made were sized and inserted into 6 inch round pipe.
The material must be suit coat lining type material or something very similar because you can't hardly blow air thru it yet it's so flimsy it collapses immediately flat as a pancake when fan shuts down.

I used plastic For Sale Sign material to create the custom sized tube because it's water proof.

Make sure when constructing your tubes that they are long enough (say 7 to 8 inches) so they do not 'roll over' inside your 6 inch pipe when the fan turns on. There's a lot of vacum inside the return pipe when fan turns on.

I have forced hot air heat at my house.
1 air handler unit is in my attic so I'm going to build one for the 'return' filter register which is 2ft x 2 ft square and located in my 'ceiling' of all places.

When the heat is on the material will lift straight up into the air..
When the heat dies, it'll flop down over the opening to stop any unwated drafts coming back thru the 'return' from my attic air handler.

I'll have to get creative with this one though and use string to stop the cloth from opening 100% when the heat is running cuz I want to make sure the cloth collapses 'in on itself' when the fan turns off.

so great. I'm glad you liked my little kick butt damper.

The ones I've installed at my house are doing a killer job.

I even built one with double layer of material just to see if the double layer of material would allow it to open all the way and it not only opened FULL OPEN when fan was ON but collapsed completely after fan off making even a better seal.

so consider using a double layer of fabric for better insulater when wrapping your custom made plastic tubes.

Just more info here..
for 6 inch round pipe dampers you would want to cut the material 20 inches x 24 inches to wrap around the tube if you are going with a single layer of material. About 2 inches of that material will be overlapped when taping it to the tube.

When you are done taping it to the tube and pushing the cloth back thru the tube you'll have about 12 inches of material sticking out the end of the tube which is the part of the cloth that collapses with fan off.

If you don't leave at least 12 inches sticking out of the tube you won't have enough cloth there to block the opening after it collapses.

Just to play it safe...
After inserting the damper into the 6 inch return pipe I reached in the hole with a piece of duct tape and taped the bottom of the cloth to the metal pipe to stop the cloth from blowing back the wrong way. Highly doubt that would ever happen but just in case.. I taped it down.

Take care and good luck to everyone on your missions.

solarhotairpanels 11-10-13 08:10 AM

Should I decide to build new or customize my current hot air collectors I can tell you this..

The design of my return air flow chamber will be totally different next time around.

I really believe the cold air that wants to drop back into the house from the collector needs to be balanced out with and UP chamber of equal size and height.

My thinking is that cold air can't flow DOWN if it has to push the same volume amount of air UPward.

The cold air becomes 'trapped' in place.
Trapped cold air to me = NO downdraft at all unless you're heating system is forced hot air..

Homes with forced hot air heating are going to want to pull cold air out of the collector into the house anytime their fans are running so backdraft dampers installed in the hot air collectors are a necessity.

but homes with other type heating systems like forced hot water, radiators, radiant heat etc. that do not heat by movement of air are less prone to want to yank cold air out of the collector into the house.

Sure wish I didn't have forced hot air heating here.. (Grrr!)

Any future hot air collectors I build will have both Supply/Return holes at the TOP of the collector probably or designed in a way to TRAP or BALANCE the cold air in the chambers and ductwork.

Incoming air from house will connect to the back TOP of the collector and forced into traveling 'down' to the bottom of the collector then around an internal baffle or 2 prior to being sent back into the house.

Phantom 11-12-13 09:27 AM

Great job I need to take the vent cover off the kitchen vent and see if I can do something similar. The vent does have a flap to help but when the wind blows I can hear the flap bouncing around allowing air to pass into the house.

solarhotairpanels 11-12-13 09:47 AM

If you're talking about the vent over the 'stove' I would be careful there.

I'd use a fire retardant type material if I were building one for that vent.
I'd also make it so you could get in there and pull it out for cleaning or replacement because of stove grease may build up on the cloth over time.

just a thought?

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