Puzzling ice formation on outside of walk-in freezer ceiling

[jbannert]

I need some ideas to explore. Why would ice form on the topside of a walk-in freezer? The walk-in freezer enclosure is constructed of plywood with sprayed-on foam insulation facing the freezer space. Over the years, over a foot of ice built up leading to the ceiling collapse. There is about 3 feet of unvented space above the freezer ceiling to the roof.
Thanks.

[US Iceman]

Why would ice form on the topside of a walk-in freezer?

This is why this happens.

The walk-in freezer enclosure is constructed of plywood with sprayed-on foam insulation facing the freezer space.

Plywood and the foam is porous. Moisture travels through the materials until it finds a cold spot below freezing. Then the ice starts to form.

Before you ask what can I do, my suggestion is to call a professional refrigeration contractor and ask them for a quote on freezer room built for this purpose. There is no comparison to the metal preinsulated panels with what you have. Anything less than this is just throwing good money after bad.