Reducing duct size

[rockrbob]

There is a section of basement that I would like to remodel and put in a bathroom. Problem is the 6" x 12" sheet metal ductwork hanging from the joists that reduces the available headroom (1920's style house -- 1950's style ductwork -- looks like asbestos tape at the seams.) I was wondering whether I could a)cut the sheet metal ducts in half horizontally and simply telescope the two sections and refasten to create ducts that are 3" x 12" in depth or b) can I remove the old ducts and replace with thinner models. One section of this ductwork crosses the joists, then it makes an L and runs parallel to but still under the joists. This ductwork appears to feed the kitchen and part of living room, but I can't tell whether it supplies the upstairs.

Any insights or suggestions would be appreciated.

Pictures can be seen here:
http://ductwork.homestead.com/index.html

Thanks.

Jim

[HayZee518]

You may be able to find a trunk reducer at "Duc-Pac" - if not then you'll have to get one made - If you reduce the duct size you may just increase the air flow through the duct or suffer from a back pressure which isn't good either.

[imeduc]

You have two room there on that 6"X12" You cant cut it down to that 3"X12" no way you have 72 sq" there now so you need that big.


ED

My mistakes dont define me they inform me.

[rockrbob]

Thanks for the replies.

So replacing it with a 3"x24" would work? Are those types of ducts available ready made or do they have to be constructed on site?

Jim

[LazyPup]

Do to the increased wall frictional losses a 3 x 24 will not transmit the same volume as the 6 x12