I am not hating on metal pipe but flex duct is more practical in many applications.
Cfm flow flexible vent vs sheet metal ducting.
I am the owner of a home built in the 50 s.
We have the original galvanized sheet metal ducts in our basement for the hvac.
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.
It all depends on the unique needs of your home and your budget.
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.
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.
Duct elbows square throat no.
We can tell it s gotten worse than at 4 compression because the scale of static pressure has increased.
Also i think spider webs are more likely to form in metal versus flex.
Last take off run to be located 12 18 from end.
While flex ducts work best for short runs in a trunk and branch system metal duct works best for entire air distribution systems.
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.
Never locate ducts at the end of the trunk line run.
Use insulated duct or duct board in unheated spaces.
Flexible ducts are fairly easy to install and will often cost less than the rigid ductwork.
Always stagger take off ducts by 12 to maintain pressure.
It was suggested by a moisture control co to have the ducts looked at some needed to be repaired.
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.
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.
So far we have gotten 4 estimates 2 companies say we need to tear out all the old ducts because they are.
While sheet metal ductwork tends to be a better long term choice flexible ductwork has the advantage of relatively low upfront cost and versatility.
Flexible duct work must be stretched tightly for maximum air flow.
I have seen many leaky metal ducts in crawl spaces as well.
Metal ductwork needs design measurement and installation by or with the help of an hvac professional.
At 4 compression it rose to 0 8 i w c.
In order to maintain velocity reduce duct size.
