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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 19068
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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I'm reworking my heating duct, and I had a question about

Customer Question

I'm reworking my heating duct, and I had a question about proper sizing. Currently, there are 2 branches of 10" flex duct going to 3 rooms each.I plan on changing this all to rigid, but have just one branch to 6 rooms. Will this be adequate or do you suggest to do 2 10" branches like it is currently setup?
Submitted: 5 months ago.
Category: HVAC
Expert:  Rick replied 5 months ago.
Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.You need to maintain the same cross sectional area that you have now 2 10" round is barely big enough to handle 6 rooms. If you want to do it with 1 branch the duct should be ~160 sq. in. (8' x 20" if you use common prefab sizes )
Customer: replied 5 months ago.
I see. So definitely, stay with the 2 branch lines then.The previous contractor used flex duct for all connections, including the branch. By changing to rigid, would my airflow be better? It's very limited right now.
Expert:  Rick replied 5 months ago.
Changing to round rigid won't make a significant difference as long as the current flex is not squashed at any point.
Expert:  Rick replied 5 months ago.
Do you have any more questions?
Customer: replied 5 months ago.
Hi Rick. Can you please pass me on to a different expert so I can get another opinion? Thanks.
Expert:  Rick replied 5 months ago.
If you'd like a second opinion please post a new question on this topic
Customer: replied 5 months ago.
I'd like to know the benefits of flex duct vs rigid duct... Again another experts opinion.Thanks.
Expert:  Rick replied 5 months ago.
The site requires that you post a new question if you want a second opinion. The advantage of flex over rigid is that you don't have to insulate flex and it's easier and cheaper to install. There is no meaningful difference in flow between the 2.If flow to these rooms is inadequate there are likely other issues at work. They could include, inadequate return air capacity, inadequate blower capacity, poor overall duct design.

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