[OP]
Contributor
Replacing the grill ("diffuser") over an air supply duct in an older home is often a nuisance because the screws that hold it often do into deteriorated wood or sometimes into nothing except plaster or drywall. ( e.g. diffuser: https://www.homedepot.com/p/Venti-Ai...-306351325-_-N )
In remodelling, where the old duct work has been completely removed, what's a good scheme that will avoid this problem? Are there designs of ducts and diffusers that are better than others?
Contributor
When I live in a duplex they had added ac in 1965. The grille on the return as attached to a substantial frame with two small studs welded to the frame. Two acorn nuts held the grille on for filter changes.
I just repalced my kitchen vent hood, it was about twice as heavy as the new unit.
Bill D
Moderator
In the 250 year old portion of our home which is stone exterior and plaster interior, the duct work (added later of course) has wood trim that was put in place to support the registers and returns...it's just simple 1x2 or 1x3, depending on the location, but it provides a solid substrate to support the metal grills and hold the screws. This trim is painted the same as the baseboard.
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
If the old ductwork is gone, why not patch the hole and get rid of the grille? If you want the grille, cut some narrow strips of wood (I use plywood so it doesn't split-1/2" baltic birch works good) and put it behind the sheetrock or plaster overlapping the hole on each side. Use some construction adhesive to hold it in place. Let the adhesive cure good and screw your grille to the plywood strips. I use a similar process to repair holes in sheetrock.
[OP]
Contributor
I still need to heat and cool the rooms. The old ducts were rusted through due to being used for 60 years with an evaporative cooler. They need to be replaced with new ducts..Originally Posted by Bob Vavricka
It easy to find web videos that show installing ductwork in new construction before any drywall has been put up or installing it in basements where it is exposed. However, in this house, the old ductwork was in a framed cavity above the ceiling and below the ceiling joists. I don't see how sheet metal ducts can be installed without tearing open this cavity. There are plenty of videos showing people assembling sheet metal ducts on a tabletop or on the floor. It's a mystery to me how to make connections to sheet metal ducts using "drive strips" when you don't have access to all sides of the ducts. Perhaps my project can be done using only slip-in connections and flexiduct.
Contributor
OK, I didn't understand from your original post, that the duct work was going to be replaced.
Why not just use stainless steel screws....
Lee Schierer
USNA '71
Go Navy!
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Contributor
I would suggest the flexible fiberglass insulated duct. Kind of like dust collector hose. This assumes there is enough room in the chase to use round duct. Does anyone make rectangular duct in flex?
Bill D.
They do make it!
https://www.buyductings.com/rectangular-flexible-duct/
Flexible ducting will increase air flow resistance and can cause a loss of efficiency in you system.
Lee Schierer
USNA '71
Go Navy!
My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute
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