Duct size

Old 03-18-19, 10:08 AM
Thread Starter
Join Date: Sep 2018
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Duct size

Replacing my furnace with high efficiency. I am not doing the install but am replacing some of the ductwork or all for that matter. Was wondering what size duct I should use. The bedroom currently has 6 metal and the kitchen as well. They are both 125 sq ft. Should I jump up to 7 pipe? According to all the CFM charts I looked at, 7 is the right size
Old 03-18-19, 10:21 AM
Join Date: Oct 2016
Posts: 2,183
Received 199 Upvotes on 181 Posts
There are no generic charts for duct system design. And it’s not about guesswork or opinions.
Duct is layed out via room by room manual j calculation, used with a manual d.
This will tell you the heat load in each space.
Getting off subject but there should also be returns in each room except kitchens, laundry rooms and bathrooms.
Old 03-18-19, 10:38 AM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
Posts: 5,491
Upvotes: 0
Received 8 Upvotes on 8 Posts
use the size that will move the amount of air you need for each room.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: