Flexible Furnace Ducts

[DebMD (banned)]

I have non flex-metal ducts. What type is yours and what's wrong?

Is the flexible plastic or metal?

[The J]

Flex is normal. It's been used for quite sometime. It's a standard part of HVAC installation.

[The J]

Jan 29, 2011 11:41:17 GMT -5 Lady Gaga Gaga Snerd said:

There are crap. They are aluminun foil with some insulation wrapped over a cheap, crappy piece of coil. Kind of like the the ones used to vent the dryer. Garbage, garbage, garbage. Big mistake. And, when I contracted the furnace, we discussed "duct work" and I said "metal ductwork" and the cold air return is metal but all the runs are the garbage-ola garbage flexible, cheap, garbage "ducts". Did I mention they were garbage?

I did HVAC work in the past. If they used all metal ductwork, it would've cost three times as much, and they would've had to cut and reframe major sections of your walls/ceilings/floors (depending on the location of the unit).

[Jake 48]

I did HVAC for over 20 years, still dabble in it part time. I would recommend insulated metal duct for the main runs, insulated metal ducts for the branch, the last 3-4 feet it is OK to use the flex to make the connection to the diffuser. The major reason for the metal duct is pressure drop( volume of air) through the system, smooth duct= less pressure drop, flex duct has a high pressure drop through it. Too much pressure drop(volume) will cause problems w/ central air, coil icing up. Same goes for the return duct, if it is not sized properly, insufficient air getting back to the system. what did you have installed?

[Mad Dawg Wiccan]

I spent over 20 years in the building maintenance industry. "Flex" ducting is exactly that, flexible. It is by nature thinner than "hard" ducting to let it easily bend, but there is utterly no reason flex ducting cannot be insulated as well as hard ducting. It's all a matter of how well you wrap it in insulation.

[Mad Dawg Wiccan]

<<And, another point is water damage? What if these garbage-ola things get wet?>>


Then you have a leaking roof. Contact a roofer and stop blaming the HVAC contractor for things beyond their control.

[ysi]

They are fun if you have a new kitten. Buy about 10feet worth and snake it around the living room floor.

[Mad Dawg Wiccan]

<<They are fun if you have a new kitten.>>

LMAO, I never thought of that but I'll bet they would be!

[rovo]

Do we have some HVAC people on this board? If so, I also have some questions about ductwork and the terminology used to describe ductwork.

[Mad Dawg Wiccan]

I was not specifically a HVAC worker, but I worked many years in facilities maintenance. Ask away, I may or may not be able to answer.

[rovo]

Sorry for the delay but I was awol.

Ducts located in an unconditioned space (attic) have to be insulated per code. Does anyone know what the "R" factor needs to be on the ducts? Might this be variable depending on the state building codes?

[Mad Dawg Wiccan]

I'm quite certain it varies. You should be able to call a local HVAC contractor and ask what the code for your area is.