Cfm Flow Flexible Vent Vs Sheet Metal Ducting

Metal ductwork needs design measurement and installation by or with the help of an hvac professional.

Cfm flow flexible vent vs sheet metal ducting.

Flexible duct work must be stretched tightly for maximum air flow. Never locate ducts at the end of the trunk line run. 810 cold air boot collar duct 45 65 el air flow dynamics duct sizing reference guide supply or return duct size capacity 09 to 10 pressure drop per 100 el. While flex ducts work best for short runs in a trunk and branch system metal duct works best for entire air distribution systems.

Always stagger take off ducts by 12 to maintain pressure. I am not hating on metal pipe but flex duct is more practical in many applications. I ve only been building since 1995 so i can t say for certain why we left the sheet metal guys behind but i suspect it was manly for cost reasons. Flex duct 05 on most metal duct calculator round metal pipe 06 on most metal duct calculators field duct sizing chart rectangular sheet metal duct 07 on most metal duct calculators.

It all depends on the unique needs of your home and your budget. So far we have gotten 4 estimates 2 companies say we need to tear out all the old ducts because they are. We have the original galvanized sheet metal ducts in our basement for the hvac. Also i think spider webs are more likely to form in metal versus flex.

Use insulated duct or duct board in unheated spaces. While sheet metal ductwork tends to be a better long term choice flexible ductwork has the advantage of relatively low upfront cost and versatility. 16 up to 11 40 el 12 to 15 55 el 16 to 21 75 el 22 to 27 100 el 28 to 33 125 el return air system no. We can tell it s gotten worse than at 4 compression because the scale of static pressure has increased.

In order to maintain velocity reduce duct size. Flexible ducts are fairly easy to install and will often cost less than the rigid ductwork. I have seen many leaky metal ducts in crawl spaces as well. Duct elbows square throat no.

At 4 compression it rose to 0 8 i w c. I don t know why but i have taken metal pipe apart to find a lot of crud which i don t think would live in flex duct. At 0 compression the maximum static pressure was 0 225 i w c. First let me start by saying i am not in the hvac business.

The performance of flex duct at 15 compression is significantly worse than sheet metal and also worse than flex at 4 compression. I am the owner of a home built in the 50 s. Last take off run to be located 12 18 from end.