How can I seal this

I have had issues for years with my upstairs unit not being able to keep the house anywhere near what I have it set for. after 2 extremely high light bills and Multiple service calls and $2000 almost to replace a recalled evap coil and no matter what it never worked correctly. Today I was halfway in the intake looking at the coils while the system was running and realized if I block the entrance to the intake the insulation sucked in and it started pulling 130 degree air from the attic. I started pulling on the stiff fiberglass board (don't know the name of it lol) and it's not secured in any way.

The air handler is built into a closet that is open to the attic above it. I guess they built the filter and intake box after the closet was built and it's not taped together or anything so it's just pulling attic air in once I put a filter in it.

The 2 hours it ran while I was looking at it the house cooled to the set temp and satisfied. It never does that on the 105 Florida days lol.

So my question is how can I seal these pieces together without tearing down the wall and rebuilding it all?




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It's duct insulation.

The thing is that the duct itself is sealed, well mostly, so the seams/joints of the insulation are not really open to the exterior environment so I would not think your getting that much leakage. You could just seal any openings in the metal ducts with electrical putty or foil tape to make them air tight.

But that being said If you wanted to seal the insulation an exterior caulk could be used.

 

i think my issues is they are poorly friction fit together then, if i cover about half of the intake you can see some for insulation move and physical feel the streams of hot air. the bottom seams are the worst. where the tape is is about a 1/4 inch gap and all 3 sides of that seam. bad enough that the upstairs stays 3 degrees hotter all day than the thermostat with a week old filter in but satisfies fine all day if the filter is out.

I just needed something that could properly stick and seal this stuff as i cannot access the other side of the box without tearing out drywall. i have plenty of caulk and expanding foam lol

 

Hi, it’s a bit hard to tell what’s going on from those pics, but you don’t want any return air going into the AH that’s not coming from the conditioned space, so do what ever it takes to accomplish this.
Geo🇺🇸

 

what im thinking about doing today is getting some 1/4-1/2 backed foam board and putting over the current insulation. i have a 3/4 inch lip all around it so itd fit and id easily be able to tape and seal that.

it was just 82 degrees up there when its set for 78, pulled the filter and in 20 minutes it dropped to 78 and satisfied.

 

I recommend picking up a bucket of duct mastic to seal that duct.


https://www.amazon.com/Red-Devil-084...s%2C379&sr=8-3

 

Hi, not sure if that insulation is fireproof.
Geo🇺🇸

 

There doesn't appear to be a flame retardancy issue.

Red Devil 0841dx safety data sheet - pdf