[cp99]

I am in process of replacing the entire HVAC system. I understand there are few types of DUCTS. What do people recommend?

Thanks

 

[user_12345a]

Doesn't matter as long as they're sized and installed right.

 

[SeniorSitizen]

Ours are the best ( PVC pipe ) and that's how we're able cool the house with a 2.5 ton unit that's 35 years old when the outdoor ambient is 112°F.

 

[roughneck]

I don’t know that PVC pipe is allowed by code.
But ideally you’d have a metal trunkline with either metal or small sections of flex for takeoffs.
The duct needs to be properly sized. Manual D with a room by room manual J is used for this.

 

[surferdude2]

I don’t know that PVC pipe is allowed by code.
But ideally you’d have a metal trunkline with either metal or small sections of flex for takeoffs.
The duct needs to be properly sized. Manual D with a room by room manual J is used for this.

When used in underground installs it works real well. We put it in a single story office building once. I've never seen it used otherwise but I haven't seen lots of things. It would be a lot harder to install above grade for sure. It could very well be shot down for possibility of toxic fume spread if burned.

You can probably find a better answer in the link below... I didn't have time to read it before it bored me to nodding.

Some Duct Info

 

[roughneck]

When used in underground installs it works real well. We put it in a single story office building once. I've never seen it used otherwise but I haven't seen lots of things. It would be a lot harder to install above grade for sure.

Mainly related to fire/flammability as far as its use, or lack thereof, so I remember.

 

[cp99]

This link https://www.allyearduct.com/blog/4-types-of-ducts-for-central-ac/ has the following:
Fiberglass Lined Air Ducts

Fiberboard Air Ducts

Sheet Metal Air Ducts

Flexible Air Ducts

Anyone know more about these?

Thanks

 

[user_12345a]

deleted.

 

[Porsche986S]

I am also going through which duct is right phase as I am going to have my 24 year old HVAC system replaced . I am no expert but it seems like at least here in the south they like to install the flex duct . In my opinion they do so because it is quick and relatively cheap . Does it work ? Yes . Is it the best ? I don't think so . When strapped for support it can easily crease/fold/bend and that creates a restriction . Even if it looks good when new time/gravity work against the sidewalls and it can sag .

Fibre board is also used a lot I think because it is easy to cut and you tape it up and good to go . But I think a metal trunk is much better but is more time consuming to cut/install . I also like metal duct work , it is strong and smooth on the inside . Around here in Georgia I am getting crazy stupid pricing for metal duct . So on my install ( haven't purchased yet ) I will insist on a metal trunk and they can tie into my existing flex duct . At some point in the future I will replace one by one with metal .

 

[surferdude2]

From a practical standpoint, it's good to run hard duct on rough-in stage but on refit jobs it makes flex duct the better choice.

On long suspended spans, it must be supported with the 2" wide straps as opposed the the smaller width stuff or even plumber's tape that I have often seen. Every 16" or 2' is best but no longer than 4' is a good arbitrary maximum for support spans. If done properly, it'll look good and stay good. The ones you see sagging weren't installed properly.

To each his own, hard duct is always better quality but if you aren't doing it yourself, that type of installation will cost more than most people want to pay.