Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

matching suppy and return size

waynemanwayneman Posts: 17Member
I have 1 unit apt. with forced air heat.Furance is in basement. Some rooms have 2 supply lines with floor vents and some have one. The return is one floor return in a room without supply line( kitchen). I would like to add cold air returns in as many rooms as possible. I have read using floor joists is not the right way to go because hard to get good seals.Should returns pipe sizing match supply size?? example. if room feed with 2- 6" duct it looks like 1-8" return would handle about the same volume of air. any thoughts??
sealed Joist??
round vs. Rectangular piping
tin vs. flexible insulated tubing??


  • pecmsgpecmsg Posts: 907Member
    Matching is just like guessing.

    Manual "J" For Load Loss calculations
    Manual "D" covers Duct Design
  • waynemanwayneman Posts: 17Member
    so I have to Hire someone to calculate those?? duct work air volume in- matching duct work air volume return does not work?? 6" duct air flow 120cfm x 2 ducts means 8" duct air flow 300cfm would handle return.
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!