# Best way to patch removed collar hole in plenum



## WyrTwister (Jul 22, 2013)

Probably a dozen ways to do it . If careful , you could even use the " plug " you cut out at the new location for the collar .

I would cut a " plug " to fit and use shiny aluminum foil tape to seal the " seam " . 

If you cut the " plug " about 3" - 4" too large & then cut back the fiberglass leaving the fiberglass the same size as the hole . You then have a foil " flap " to overlap the existing duct board . Seal with foil tape .

If you are concerned , cut a larger rectangular piece to cover it . Tape it into place .

God bless
Wyr


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## supers05 (May 23, 2015)

I would never use duct board, so it would be a square piece of sheet metal, 8 screws, and tape. If I'm really lazy, I'll leave the takeoff there and just put on a cap. 

Cheers!


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## tearitup (Jan 4, 2015)

Thanks guys.
* WyrTwister - correct, a bunch of ways.
Using the plug from new hole - problem is, it's same size & both have square sides. Nothing to keep from falling thru, unless plug is screwed to something larger, like sheet metal or...

Only question about cutting away fiberglass & leaving a flap is, sometimes the paper / foil isn't hard to separate from the fiberglass. Esp. a patch on top of plenum - only thing holding the fiberglass up (dangling in the hole) is its adhesive to the paper skin. Which may be OK?!

* Supers05 - don't you then insulate over (or under) the sheet metal patch?
Which seems like as much work as using duct board.
Here, metal will sweat like hell ( NO good), even if you don't care about the cold / heat loss thru uninsulated metal.
Maybe I misunderstand your process?

Or ?... screw / fasten a (correct size) duct board plug TO sheet metal - slightly larger than hole? Then tape or mastic the sheet metal to plenum.

In humid climates, I'd worry if cold AC always got to HOT bare metal in attic, drips inside the plenum (not a drip pan) - cause mold. Mold in systems here can be a big problem.


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## WyrTwister (Jul 22, 2013)

tearitup said:


> Thanks guys.
> * WyrTwister - correct, a bunch of ways.
> Using the plug from new hole - problem is, it's same size & both have square sides. Nothing to keep from falling thru, unless plug is screwed to something larger, like sheet metal or...
> 
> ...


 Again , many ways to do it . We have spent more time talking about it than it would have taken to do it .

God bless
wyr


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## tearitup (Jan 4, 2015)

> many ways to do it . We have spent more time talking about it than it would have taken to do it


You are correct, Sir! (ala, Ed McMann).
Except in many yrs of construction, remodeling, repair (not HVAC), I've seen many "fixes" for given problems. When there are structural and / or water, moisture issues involved, a large % of the quick fixes lead to problems.
The builder, repairman or installer is long gone, w/ the $.
The homeowner or next buyer foots the now extensive repair bill.


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## supers05 (May 23, 2015)

We would buy the duct with insulation already inside it, to the depth required by the situation. (typically 1-1.5") The insulation is not used structurally. 
For a patch like that, I'd tape a piece of insulation on the outside. 

For your case, you could screw the patch onto a sturdy substrate, and it'll hold the patch in place. 


FYI: The duct would sweat on the outside during the a/c season, and may or may not sweat on the inside during the heating season. It's common in flue vents, In the worst cases I saw, the droplets would freeze and clog the vent. 

Cheers!


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## tearitup (Jan 4, 2015)

Thanks all.
Was mainly concerned of patching the wrong way.
Sounds like several ways will work.


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