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Old 06-14-2012, 10:24 PM   #1
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Seal and insulate or replace ductwork?


I'll make a very long story short and jump to the bottom line. The HVAC contractor did such a poor job with the ductwork that the unfinished basement never gets above 65 all summer. And that's with it being on its own zone that's never been used.

I could seal all the leaking joints and insulate the runs but discovered something. Insulated flex duct costs pretty much the same as just insulation for 6" and 8" round ducts. Obviously, it would also be less work than trying to seal the ducts and then slide duct wrap onto them.

Is there any reason why I shouldn't simply remove the metal ducts and ziptie flex duct to the elbows coming out of the trunks and to the floor register boots? At least then all I'd have to seal are the zone trunks and wrap them with insulation.

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Old 06-14-2012, 10:50 PM   #2
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Seal and insulate or replace ductwork?


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Originally Posted by TheCheezWhiz View Post
I'll make a very long story short and jump to the bottom line. The HVAC contractor did such a poor job with the ductwork that the unfinished basement never gets above 65 all summer. And that's with it being on its own zone that's never been used.

I could seal all the leaking joints and insulate the runs but discovered something. Insulated flex duct costs pretty much the same as just insulation for 6" and 8" round ducts. Obviously, it would also be less work than trying to seal the ducts and then slide duct wrap onto them.

Is there any reason why I shouldn't simply remove the metal ducts and ziptie flex duct to the elbows coming out of the trunks and to the floor register boots? At least then all I'd have to seal are the zone trunks and wrap them with insulation.
poor idea in my opinion....

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Old 06-15-2012, 06:08 AM   #3
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Seal and insulate or replace ductwork?


Basically, if you want to rerun them in flex. You need to go to the next size larger flex duct to get the same air flow.
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Old 06-15-2012, 10:08 PM   #4
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Seal and insulate or replace ductwork?


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Basically, if you want to rerun them in flex. You need to go to the next size larger flex duct to get the same air flow.
Drat! I was afraid of that. All the elbows are on top of the trunks so that would mean dropping them so larger elbows could be installed. Would it also mean the trunks would have to be resized? This just keeps getting better.
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Old 06-15-2012, 10:13 PM   #5
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Seal and insulate or replace ductwork?


Trunks would be ok.
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Old 06-16-2012, 08:46 AM   #6
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Seal and insulate or replace ductwork?


Before you do anything, perhaps you could conduct a little experiment. On a warm day when you won't be home, leave your a/c off. See what temperature the basement gets. Then you can decide if the difference is worth all the trouble.
I might seal the joints but i dont think insulating the ducts will help much, unless they are sweating.
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Old 06-17-2012, 08:43 PM   #7
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Seal and insulate or replace ductwork?


With the AC off the basement has reached the mid to upper 70s. When the AC was turned back on the trunks would sweat -- not to the point of dripping but damp enough to see if a hand was wiped on them. I never "wipe tested" the register runs as they're up between the joints and out of reach without a ladder. The duct sweating stops once the home's humidity drops enough but by then the basement is super chilled. It's been as cold as 57 (that I've noticed).
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Old 06-17-2012, 08:50 PM   #8
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Seal and insulate or replace ductwork?


Yikes!
Well, here's what I'd do:
Paint the joints with duct mastic.
Then wrap with one layer of bubblewrap (also called "reflectix")
Its only R-4, but this is enough to prevent sweating, and its very easy to work with.
Metal ducts are easy to clean, whereas flex ducts aren't. I wouldn't switch.
Hope this helps.
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Old 06-17-2012, 09:01 PM   #9
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Seal and insulate or replace ductwork?


Thanks, that pretty much sums up what I figured. I didn't want to kill the idea of flex ducts but had thought of the cleaning problem they may introduce. I've never had ducts cleaned before but with pets in the house... it could happen.

Thanks again.

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