[ddawg16]

After reading some of the posts here on flexible duct, I think I know the answer.

As part of my 2-story addition, I need to run some HVAC ducts in the addition.

Except for the run from my FAU to the addition, all the ducts will be either in the floor (2nd floor) or in soffits. In other words, non of the duct will be in exposed areas. I do have one area...basically it's a 5x1x9' that has a bunch of plumbing pipes in it but the outside walls are insulted.

So...I'm assuming that I'm better off using hard duct instead of flexible inside the walls and soffits...

So...do I insulate those ducts? Is there going to be a significant heat loss if I don't?

Side note...the 2nd story sub floor will be insulated....

 

[bobinphx]

hard ducts (steel, not fiberboard) will out last plastic every time.

insulating ducts in conditioned spaces if often times noted as not needed. If it was me, I would insulate them. The cost is marginal.

I would urge your to be sure to secure and seal all rigid ductwork. There are minimum code requirements about number of fasteners, type of fasteners and various sealing substances (ie mastic and tape).

bottom line, use a lot of sheet metal screws, a lot of mastic and mesh tape and a lot of aluminum tape!!! then insulate, even if the ducts are inside.

just my two cents worth...

 

[SeniorSitizen]

PVC pipe - no leaks - smooth sailing air flow

 

[techpappy]

OP...Quote from your post...."but, the outside walls are "insulted" lol:laughing: hope the walls forgive you:laughing: amazing what some typos result in...sometimes they can be downright embarrassin':laughing:

 

[ddawg16]

That is what happens wind we depend on spell check.....doesn't due much for grammar.

 

[beenthere]

Outside wlls aren't always sealed as well as they should be. So I'd "insult" that duct too. LOL. For the low cost of insulation, its good protection against condensation when your using the A/C.

 

[ddawg16]

A/C? Here? I don't need AC.....I'm 4 miles from the beach....heat only.

So....use hard wall but insulate?

and....PVC? I've never seen PVC for HVAC ducts

 

[beenthere]

I've only ever used PVC duct for under ground.

Yes insulate your hard duct in the sofit at the outside wall.