Reducing Ductwork Size - Implications? - HVAC - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC


Thread Tools Display Modes
Old 03-24-2009, 05:30 PM   #1
Join Date: Mar 2009
Posts: 1
Rewards Points: 10

Reducing ductwork size - implications?

About a year ago my wife and I purchased a house built in 1959 that has rectangular metal ductwork (uninsulated), the main portion of which runs mainly lengthwise through the middle of the house. This ductwork is mostly exposed in the partially finished basement. It measures approx. 9" high x 20" wide.

We're planning on eventually doing some remodeling and I'd like to replace the ducts with lower-profile ducts and returns, and build soffits around them where they will hang below the ceilings downstairs. I may also want to adjust the location of two or three upstairs vents, but only by a couple feet or so.

Would I be greatly impacting the efficiency of the furnace? Any chance of harming the furnace by it having to force air through a smaller channel? It appears that the current furnace - a Trane XV90 - was installed in 2003. There is also a Trane AC unit on the outside of the house.

I've seen rectangular and tubular ducting. For interior runs (not attic or crawlspace) does insulation matter? What type of ducting should I be looking at? I'm generally pretty handy, but know next to nothing about HVAC systems. Am I biting off more than I can chew?

Thanks in advance for the advice!

HVAC Neophyte


wdbdesign is offline   Reply With Quote
Old 03-24-2009, 06:40 PM   #2
Join Date: Oct 2008
Location: Suburbs of Detroit Mi
Posts: 3,704
Rewards Points: 2,000

I'd have a pro come by and go over that plan. To me you seem to be taking a lot away from the air flow with what you propose.


hvaclover is offline   Reply With Quote
Old 03-24-2009, 07:17 PM   #3
An old Tradesmen
Join Date: Oct 2008
Location: Somewhere
Posts: 34,578
Rewards Points: 8,142

9" high by 20" wide= 8" by 24", or 7" by 29", or 6" by 35".

8" won't gain you enough head room to even notice.

7 and 6" would be special order, or sheet metal shop only.
Its not common.
beenthere is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
need help with package unit ductwork bekind42 HVAC 15 11-04-2011 03:13 AM
Size of whole house fan needed Doug Crf General DIY Discussions 20 02-25-2011 11:29 PM
duct work size justmefixin HVAC 2 09-20-2008 06:59 PM
reducing pipe size for sink drain bluebee1314 Plumbing 5 12-02-2007 12:53 PM
Reducing size of very large air-vent returns in floor? AllGoNoShow HVAC 3 09-19-2006 09:36 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1