DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (
-   HVAC (
-   -   Flex Duct Advice (

ssporty21228 07-23-2008 01:06 PM

Flex Duct Advice
I want to replace flex duct in my attic that's old and deteriorating. I have 1600 sq ft. 3 bedroom 2 1/2 bath home with a pyramid style roof and the coil about centrally located in my attic. My question is this... what size diameter flex duct do I use to get the best deliver of cold air to the different rooms of the house....?

Currently in my living room there's 8" diameter duct going to 2 registers one is approx. 15 ft. long and the other about 4 ft long, the room is 336 sq ft. with a 9 ft. ceiling.
The duct going to my kitchen is 8" in diameter and approx. 17 ft. long, the room is 130 sq ft. with a 8 ft. ceiling.
The duct going to my master bedroom 9" in diameter and approx. 14 ft. long, the room is 182 sq ft. with a 9 ft ceiling.
The duct going to my secondary bedroom is 6" in diameter and approx. 19 ft. long, the room is 130 sq ft. with a 8 ft. ceiling.
The third bedroom has a 6" diameter duct and is approx. 15 ft. long, the room being the same dimensions as the secondary bedroom.
I'm a newbie so any help or insight will be greatly appreciated!

geo fan 07-23-2008 05:46 PM

unless there is a problem with airflow in one of the rooms use the same size. R-8
and for runs over 15 feet use hard pipe wraped with 3 inch insulation

ssporty21228 07-23-2008 07:15 PM

Thanks for replying to my post Geo
So, you say replace flex duct with hard pipe for runs over 15 this because of less resistance?
And what diameter of hard pipe should I use?
And the runs that are currently installed that are 6" in diameter, should I up those to 8" also?
Also, these 6" diameter runs branch off of the 8" runs...should I continue these branches or cut new holes in my plenum to run them from?
And...the register closest to the coil is 9 degrees colder than the other registers in my this normal and what if any temp difference should there be?

geo fan 07-23-2008 07:45 PM

r8 is the flex insulation rating not the size , yes less resistance it's code here
the temp difference between registers is a product of inadequate insulation or leaky ducts ,pipe size only effects volume of air not temp. So to start from the beginning replace everything with the same size , excessively long runs should be done mostly with hard pipe of the same size with 3 inch insulation. If there is no problem with rooms being different temps don't bother redesigning the duct's just direct replacement with improved insulation rating

ssporty21228 07-23-2008 08:28 PM

For the info Geo...I'll definitely take your advice!:thumbup:

All times are GMT -5. The time now is 01:34 PM.

User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.

Search Engine Friendly URLs by vBSEO 3.6.1