Flexible Vs Sheet Metal Ducts

I do agree with what ponytl said about possibly avoiding some duct loss with flex but possibly having duct loss due to flex.

Flexible vs sheet metal ducts. Rigid metal is straight and smooth walled you have to work to crush or kink rigid metal. If any duct product should be banned it s duct board. I still don t believe in duct board. Flexible ducts are fairly easy to install and will often cost less than the rigid ductwork.

In comparison to metal duct flex duct is easier and faster to install. Sheet metal ducts are less likely to incur dangerous mold and growths because their surfaces are non porous and smooth. Most of what s being installed in new houses now is flexible ducts because they cost so much less than rigid sheet metal ductwork. Metal ducts are more rigid due to the nature of steel making them ideal to build an entire hvac system.

Flex must be oversized at least one duct size. Rigid metal is more likely to be installed without constrictions whereas flex duct can easily be pinched down. There s duct board rigid fiberglass with a foil facing but in my opinion that s worse than flex. Air flow in a flex duct tends to tumble probably because of the rib like intrusion every inch or so.

Hard duct is probably the best but most won t pay the difference for it. Flex can be good to help dampen velocity noises and it is relatively air tight but imo mastic on the old sheetmetal ducts covered by a good foil backed insulation is without question the best way to go old ducts or not. Rigid metal is not easily damaged by rodents and uv light. While they tend not to last as long as sheet metal they are very cost effective.

So it may be a wash. Btw we did replace the rusted metal duct with new metal. This is because they re more versatile and flexible. Even when doing this the flex duct creates much more resistance.

Flexible ducts are made out of corrugated plastic often wrapped in insulation. Flex ducts are better for existing trunk and branch heating and cooling systems. Alternatives to flex duct. The installation of hard ducts is also more difficult because.

Air flow in a steel duct tends to travel smoothly in a coil like motion. Well if we re not going to use flex what s left. The inner liner ribs restrict airflow more than sheet metal ductwork but not significantly. Flexible ducts are also the worst type of ductwork for airflow.

That leaves rigid sheet metal often called hard pipe. While sheet metal ductwork tends to be a better long term choice flexible ductwork has the advantage of relatively low upfront cost and versatility.