Flex Duct Questions

[Dymalica]

Question 1: Is it wise to use flex duct over lighting in a T-bar (2x4') environment? Will the flex duct burn or have problems?

Question 2: Do you size flex duct the same as round duct or is it wise to size it one size larger (12" to 14")due to the high roughness?

 

[ChrisConley]

Question 1: Wise, common and sometimes necessary. Flex duct need to be rated (smoke and fire) for the space and application.

Question 2: We typically give a limit of 1200mm (4') as maximum flex duct length. We also specify a 'hard elbow' to prevent the flex from collapsing at the diffuser. Don't typically increase the size of the flex as 4' is a fairly small portion of the system.

 

[marcoh]

Our standard spec limits velocity in flex duct to 3m/s and min 1500 and max 5000 long. Try to keep the duct as straight as possible, supported so it does not rest on the ceiling, and if it is installed correctly with generous bends there should be no issues.

Longer flexes are good for acoustics and enables easy/cheap grille locations for fitout.