Cfm Flow Flexible Vent Vs Sheet Metal Ducting

I have seen many leaky metal ducts in crawl spaces as well.

Cfm flow flexible vent vs sheet metal ducting.

Flex ducts are better for existing trunk and branch heating and cooling systems. 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 duct size. Flexible duct work must be stretched tightly for maximum air flow. 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.

In this video i ll make a case for going back to rigid metal ducts for your trunk lines and keeping your flexable ducts to the last 10 or less of a. Never locate ducts at the end of the trunk line run. Always stagger take off ducts by 12 to maintain pressure. In comparison to metal duct flex duct is easier and faster to install.

Like regular hvac duct flex duct work needs to be sized appropriately in order to flow the air volume which is measured in cubic feet per minute cfm correctly. Flexible ducts are fairly easy to install and will often cost less than the rigid ductwork. I am not hating on metal pipe but flex duct is more practical in many applications. Use insulated duct or duct board in unheated spaces.

Last take off run to be located 12 18 from end. Without it there would be tons more labor and material to make that final connection. The rectangular dimensions and the air flow volume are adapted to the equal friction loss. Also i think spider webs are more likely to form in metal versus flex.

This is because they re more versatile and flexible. Metal ducts are more rigid due to the nature of steel making them ideal to build an entire hvac system. The table below can be used to compare equivalent diameters for rectangular and round circular ducts. The table is based on the ducts friction loss formula.

Sheet metal ducts are less likely to incur dangerous mold and growths because their surfaces are non porous and smooth. Flex duct allows easy connection from the main duct trunk to the hvac grille. In order to maintain velocity reduce duct size.