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
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
- 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?
I could sort of understand the "go fuck yourself" tone of this reply if it
were posed to alt.hvac, wherein the denizens claim, that despite usenet
being an open forum for all, that homeoaners, as they style it, should stay
out, but this is alt.home.repair, and you, PrecsisionmachinisT, should keep
your condesending bullshit tone to the group afore mentioned. Seems to me
he has consulted professionals in the field (several contractors), and that
maybe you should go back to sucking up to pjm or whoever the hell it is that
runs your world. If you need any clarification about where where I stand as
regards to HVAC professionals, I have them out about once a year to check
our system, and defer to their judgement even if I have to tell them what
the problem is likely to be. It aint rocket science, but many HVAC techs
couldn't spell either one.
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 ??
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
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
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.
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 :)
Well, SVL answered your questions..... And you are one cheap
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.
That's one of the reasons the HVAC pro's don't like HO's to do their own
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
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?
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.
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
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...
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.
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.
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