Fridge and freezer refit with vacuume panels

[jpendoley]

I'm gearing up for my third fridge rebuild. I've used blue board and pourable foam in the past (with good result)s and want to try a fridge/freezer with vacuume panels. The primary reason is that I can get the same insulation value with a 1" thick panel that I can get with 6" of foam or 4" of aerogel. I would lose an unacceptable amount of space with foam. Also, the panel solution seems to be about 1/2 the cost of aerogel. I understand the risk of loss of vacuume and the need to protect the panels: my plan is to install a 1" layer of blue foam, then the panels, and then another 1" layer of blue foam. I have excellent access to the box. The panels have been manufactured by panasonic for a long time, are relatively affordable and used in critical installations requiring very low temps. They estimate a 50 year lifespan. I'm fully prepared to redo the project if the panels fail...

The one thing I am unsure about is the best way to create a vapor barrier. The VIPS should be vapor proof, but the foam is not nor the outer ply cabinet walls. I had thought of epoxy sealing the ply outer walls, but that won't stop the foam from getting wet. Would it be practical to wrap the whole shebang in a 7 mil plastic envelope, tape that closed and then secure in place? Do I just need to install a barrier on the outside face? I'm having a hard time envisioning securing the plastic bundle to the cabinet frame as nothing seems to stick to plastic sheeting-including epoxy.

I'd appreciate any suggestions on the vapor barrier front and comments about the panels. The link below brings up information about the panels.




https://mm.digikey.com/Volume0/opasd...32/U-Vacua.pdf

[sailingunity]

I ventured down the same path you did before finally buying an off the shelf fridge. I have the box mostly built but stopped when I got to the lid.

In my case I encapsulated the vacuum panels in pour in closed cell foam. I figured this would protect them well enough from damage. I hadn't gotten to the vapor barrier part yet, but you can buy vapor barrier paint which seems a better solution that plastic which you would never be able to seal perfectly.

[jpendoley]

SailingUnity-we’re you using the same panels and if so, what was your impression of the panels? Vapor barrier paint makes me wonder if just rolling epoxy on the foam faces would suffice?

[GordMay]

An impermeable vapour barrier is always installed on the warmer side of the walls. Similarly, the inside surface should never be made vapour tight. Otherwise, moisture that has entered into the insulation, though the outer walls, will remain trapped inside, and would spoil the insulation.

An excellent, and thorough, review of vapor barriers, is provided by Building Science Corporation [1], which refers to US DOE Energy Climate Zones. This is focused on residential and commercial buildings, but the principles discussed apply, generally.
[1] “Understanding Vapor Barriers” ➥ https://buildingscience.com/document...vapor-barriers

[jpendoley]

GordMay, thanks for theresponse and the linki. ts a bit of a treatise to get through though. The vapor barrier on the "outside only" is confusing to me. If cold damp air from the interior fridge space is migrating within the insulation, wouldn't it condense as soon as it hit the cool barrier film? Seems like it would collect on the inside face of the film and soak the insulation, no? Being further from the cool interior the film must be a warmer surface. If the insulation was entirely encapsulated in a vapor barrier wouldn't it be immune to whatever condensate did develop?

[GordMay]

I’m not a reefer’ tech, nor an 'envelope' expert, so I’d refer you back to the treatise.
Condensation happens one of two ways:
Either, the air is cooled to its dew point, or it becomes so saturated with water vapour that it cannot hold any more water [this has to do with vapour pressure].