Ductwork

[gordy]

Is there any reason as to why there is not a use of PVC for ductwork applications for HVAC?

Gordy

[dash]

Doesn't meet the specs of class 1 ,duct,Flame and smoke developed rating.

If there's a fire,not a good thing.Some codes allow it under a concrete slab,little fire danger.

[gordy]

That makes sense to me. So how does flexible duct get around this? Is it the insulation?

Gordy

[dmoneyc22]

i believe there is a type of duct system that is of pvc type construction you may want to contact your local dealer for info

[dash]

Originally posted by gordy
That makes sense to me. So how does flexible duct get around this? Is it the insulation?

Gordy

Just a different material,than PVC,there is a type of PVC that meets this rating,very expensive though.

[tinner73]

Originally posted by gordy
Is there any reason as to why there is not a use of PVC for ductwork applications for HVAC?

Gordy

there is pvc coated spiral duct. i don't quite get your question. what do you want to do?

[tinner73]

Originally posted by tinner73

Originally posted by gordy
Is there any reason as to why there is not a use of PVC for ductwork applications for HVAC?

Gordy

there is pvc coated spiral duct and rectangular. i don't quite get your question. what do you want to do?

[framehvac]

Originally posted by dash
Doesn't meet the specs of class 1 ,duct,Flame and smoke developed rating.

If there's a fire,not a good thing.Some codes allow it under a concrete slab,little fire danger.

Thats only for the first 5 feet.I think the price would be to much.

[Edited by framehvac on 03-05-2005 at 02:19 PM]

[gordy]

Well, I want to install AC in my attic for a 2300 square foot ranch. Looked into Hi Velocity turned off by the reduction in seer rating. So thinking conventional. Not an avid fan of flexible ductwork. Just wondering about the pvc duct work, an avenue that went through my head knew there must be a reason why not widly used.

I have read alot about ductwork in unconditioned spaces. I know its not my best option. But its doable. If done right. I have ceiling radiant heat (hydronic). My concerns with the ductwork would be A. Condensation in the winter or summer, leading to mold issues. B. Lack of performance, ductwork being warm/ hot between cooling cycles leading to longer than needed cycles.

This system would only be for AC. So I'm tryin to get my ducks in row here. Thinking of using two air handlers so I can keep my attic center unobstucted for storage. The ranch is a U shape. HeatGain 40,000 Btu high side. I presently use 30,000 Btu's worth of window shakers and it cools they handle the load.

Thanks for your replies Gordy

[dash]

The heat gain for the ducts in the attic,should have been accounted for in the Manual J,load calculation.Use an R-8 insulation,to reduce the loss.

[tinner73]

any kind of ductwork can be done. it depends how thick your wallet is. i would use standard galvanized metal that would get wrapped on the outside. i too dislike flex systems, Dash would disagree with me.

[framehvac]

Originally posted by tinner73
any kind of ductwork can be done. it depends how thick your wallet is. i would use standard galvanized metal that would get wrapped on the outside. i too dislike flex systems, Dash would disagree with me.

Its a southern thing tinner73.

[Edited by framehvac on 03-05-2005 at 03:09 PM]

[tinner73]

i understand.