Replacing flex duct with rigid sheet metal

[Jeffrey J. Kosowsky]

The previous homeowner did a DIY job of installing a new furnace using a twisted maze of flex duct to make all the supply and return runs in the basement.

Several heating contractors have advised us that flex is not intended for long runs and that this is the most flex they have ever seen. Also, there are no dampers and in some areas the flex is pinched and the insulation tearing.

Couple of questions: - Is replacing flex with rigid sheet metal duct work generally worthwile?

- Is it better to use custom sheet metal fabricated to fit tightly between the joists or should we go with standard "round" ducts? More generally are there different qualities of sheet metal that we should be concerned about?

- One contractor talked about "vinyl clad duct insulation". Is that a good insulation solution?

- What types of dampers should we be installing for best results?

- Any other questions we should be asking regarding duct work?

[PrecisionMachinisT]

Sometimes, yes........

If there are no leaks, and its not noisy, why be concerned ???

To find a solution, first one must define some *existing* problem.........

You should get them from home depot, or lowe's.........and dont be shy, be sure to ask em about contractor pricing..........

Nope, forget your local hvac contracter, his son just wants to f*ck your daughter in the ass is all.

[gene]

[Jeffrey J. Kosowsky]

Why waste time responding if you have nothing helpful to say?

Read above... several HVAC contractors and home inspector said it should be replaced particularly since ducts are pinched in several places and insulation is torn in others plus no dampers. So question is whether these reasons justify spending 3K on replacing ducts.

Well, if we replace ducts, should we insulate the new sheet metal ones? If so what insulation should we use?

Do you have problems staying on thread? I don't recall asking about price or supplier source.... If you read the post, you would also know that this is not a DIY project so why the hell would I want to go Home Depot or Lowes?

Take your mind out of the gutter or perhaps such feeblemindedness comes from breathing in too much PVC primer and cement without adequate ventillation :)

[HeatMan]

Well, SVL answered your questions..... And you are one cheap (something-or-other).

Why do you post your questions here? You say that you have had several HVAC contractors look at it. They can see it and we can't.

Read on...

That's one of the reasons the HVAC pro's don't like HO's to do their own work.

That's true. I don't much need for manual dampers around here, though

I don't know. I would in *my* house. I don't have a lot of use for long flex runs and won't warranty them on jobs the HO's or contractor asks for it.

How much money do you want to spend? Custom metal can cost 1.5 times the price of standard metal.

You mean the gauge (thickness) of the metal? Most round duct around here is

28 or 30 gauge. Rect duct is usually 28 gauge, IIRC.

Fiberglass duct wrap is on the way out and something has to replace it. The vynil clad bubble wrap looks like the replacement, but it takes training to do it correctly.

Manual dampers? For air balance? If the ducting is done correctly, you won't need dampers for balancing.

Will you be getting a performance warranty? Will the duct work be sealed? Can I get a contractors discount?

Good luck....

[Joe Fabeitz]

[m Ransley]

3 said replace it, and yes insulate it. Are they also saying it is improperly sized? Do you heat or cool unevenly? Properly sized insulated ducting is going to get you the most efficiency out of a new unit. Flex has the ridges that wont flow as much air as smooth duct so I can see an efficiency issue switching as well as the kinks in the tube and efficiency benefits. Also you posted 2.5 or 3 ton AC, Im no pro but new ducting flowing more air might make the 2.5 ton the right option, 3 might oversize you leaving you humid. What size do you have now, If 2.5 ton you may be able to go smaller with new ducts if it cools well. You need a load calculation done in writing before you proceed.

[Jeffrey J. Kosowsky]

Consider that many of my questions are about getting better quality, not sure why you would get that impression... There is a difference between not wanting to get ripped off and "cheap"

Well, contractors are in the business of "selling" you something. So, when they see something that is not right, their tendency is to sell you a new solution (not all, but many). I was hoping that I would get a less biased opinion on this newsgroup.

Your answers though were *very* helpful. [SEE MY COMMENTS BELOW]

Well, the house is very old, uninsulated, and originally was designed as gravity hot air. So my thought is that the system might need a fair bit of manual balancing.

1.5x is not that bad, considering that materials is only a portion of total cost, right?

Would you recommend going for #28 over #30, if given choice?

So, this is a good quality choice, right? Are there different grades to be concerned about?

You should better read the thread on contractor's discount -- the original question was about DIY projects not about jobs like this where a contractor is used.

[PrecisionMachinisT]

Well, lookie at who is being condecending now..........

And most of the questions were answered in his own mind before he even dropped his post, so what was the point of it all besides being mostly a little fishing expedition ??

...LOL...

Paul dont run my world, its just that on some issues we see eye to eye is all--and one of them issues happens to be in the hacking in of flex duct.......

I dont have them out even that often, but yes I too have run up against one or two techs that were questionable in the knowledge arena--the one I now use I know on a first name basis and he works for a second generation family owned company........

Ive had too many fly by nighters already, and in fact the place I bought has a hacked in mix of flex, ductboard and metal. from a long succession of alterations by hacks.

Thank you very much you can exit stage right now.

[Art]

Whatever you do, don't use the insulation that goes inside the metal duct. Can't believe that crap is even on the market. And don't use the cardboard duct stuff either if that is still on the market. As far the the flex duct, if you can shorten runs and use wider ducts it will help reduce friction in the duct, but metal is always going to be better if done properly. But both need to be planned by someone who knows what they are doing. Many HVAC guys don't even know what they are doing, unfortunately.

[HeatMan]

But you seen to be the cheap kind....

Less biased? Here? Thankfully, I wasn't drinking anything when I read that line. I have nothing to gain by posting here, I'm only trying to help by offering my opinion.

See above lines...

You didn't say that. You have a converted gravity system? They just tied the flex on to that? OMG, that's crazy....

Then you add labor and overhead.

Actually, it would depend on the application.

I haven't used it yet on any FA jobs. The ones I've seen it used on looked sloppy. I don't know about the grades, if any.

That seemed to be your concern, getting it cheap.

FYI, this is the end. Any more questions for me on this topic, email me.

[Jeffrey J. Kosowsky]

Perhaps its a matter of perspective... looking for a fair price does not make one cheap. Of course, many contractors on this newsgroup seem threatened by people who try to get a better understanding of quality and pricing...

Perhaps not less biased individually, but by reading multiple responses, one can more or less average out the bullshit and get some sense of what the real answer is. Of course, one could try to get estimates from dozens of contractors, but that would be wasting a lot of my time and their time...