I live in Michigan and it appears to be a rather frigid winter this year. We are remodeling a mst. Bath and have demo'd to the studs in the shower and the tub deck surround area. Let me add that 3 walls in this room are exterior. Just happened to pull back the faced R-19 insulation to discover that the insulation was damp and the sheathing was frosted and wet. What shall we do? Don't want to have issues down the road after investing all this time and money into this project. Thank you

Can you tell if the moisture is coming from the outside or from the inside? Your Exterior walls show have a moisture barrier, especially since this is a bathroom. What is your house sided with?

You may have a leak in the vapor barrier and humid air is leaking into the wall and freezing or you may also have an ice dam on the roof that is letting melted snow water into the wall.

The exterior of the home is brick built in 1999 but not sure if the home was built correctly with vapor barriers and so on.

One theory is that the walls have been demo's for a 2-3 week period on the interior and the heat from the interior is mixing with the cold air from the exterior creating frost on the inside of the sheathing. If this was a long turn problem I would

Have thought I would have had microbial growth?

Inspected exterior no ice dam. Thanks