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Discussion Starter · #1 ·
I don't post on this side of the forum, but I recently had a new heat pump installed in the house I'm building for myself and a couple of things look questionable to me. Maybe I'm wrong, but I'd like to know for sure before I confront the installer about it.

He's put the main duct in and it's 14" round metal, stepped down to 12", and then to 10" on the ends. It's got a silver type of bubble wrap looking insulation around it. On the seams of some of the bubble wrap insulation he's put some type of white compound. It's a hard type compound, and I'm not sure what it is supposed to do, but he only put it on the bottom side of the duct ... he put it around some of the flex duct lines running of the main duct where the flex meets the main duct.

Also, where some of the flex duct ties into the main duct line, there appears to be gaps . It looks like the outlets the flex is connected to at the main duct is a metal flange with a thin foam gasket. There's gaps between that foam gasket and the bubble wrap insulation that's on the main duct. Is that going to leak air, or is it sealed better than it appears? The last thing I want is moisture problems in the plenum between my first and second floors.
 

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Sean
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I'm not an HVAC guy

Metal duct seams should have the mastic on them - the insulation should use that special metal looking tape

Both should be around all the seams

I am sure an HVAC guy may be around soon, or they are waiting for someone to state the obvious - this thread is worthless without pics
 

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The white compound could be hard cast. Or another brand of mastic.
It should be on the seams of all duct.

The small area that may be missed between the bubble wrap and take off shouldn't sweat enough in 20 years to damage anything. If the band boards are sealed and prevent fresh air from coming in.

Since no way to know if the band boards will always be sealed properly, if ever. I like to use expanding foam on those areas, just to be safe.
 

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Discussion Starter · #5 ·
The white compound could be hard cast. Or another brand of mastic.
It should be on the seams of all duct.

The small area that may be missed between the bubble wrap and take off shouldn't sweat enough in 20 years to damage anything. If the band boards are sealed and prevent fresh air from coming in.

Since no way to know if the band boards will always be sealed properly, if ever. I like to use expanding foam on those areas, just to be safe.
Thanks beenthere ... there's also a duct installed in the second floor attic, where fresh outside air is coming in all the time through the soffit and then out through the ridge vent. It's a very, very small attic that you have to crawl around in, if that gives you an idea of the volume of space in it.

I'll get some pictures sometime today when it warms up.
 

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The 'bubble wrap' sounds like Reflectix. It is 2 layers of bubble, separated by foil. When installed, 3/4 inch spacers should be placed about every 2 running feet. This provides an air space which doubles the R value from 3 to 6.

You can determine if an air space exists by pressing the the insulation against the duct. Without air space, there will be no 'play' when pressed.

All seams should be overlapped and sealed with wide metal tape (per manufacturer's directions).

Delta
 

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Ductwork

Not knowing how much air your systems is supposed to be handling, one cannot tell if the duct is adequately sized.
 
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