Plastic in wall between different rooms in garage with significantly different temperature

[sir_erken]

I'm insulating the garage. It will have 95+45 insulation in the walls with plastic between the 95 and 45 layers, I was thinking.

The garage will be kept around 8 degrees in the winter.

What I'm considering now is a wall already insulated in the garage that separates the garage and an insulated guest room. Should this be plasticized on the garage side, on the guest room side, or not at all?

The trick is that currently, the guest room is not heated except for a few days a year, so it will be colder in the guest room than in the garage.

However, in about 5 years, the guest room will most likely be used as the oldest son's bedroom and will then be kept at around 20 degrees all year round, so it will be colder in the garage then.

How should one think?

 

[KnockOnWood]

I think you should plasta.

 

[Rabbithole]

And the plastic is normally placed on the warm side

 

[sir_erken]

But in this case, for the next 5 years, the warm side will be the garage which stays at 8 degrees. Then it will probably be the room that is the warm side, maintaining 20 degrees. So, on which side should the plastic be placed?

 

[sir_erken]

Any thoughts on how to think here? Plastic on the garage side or in the guest room?

 

[KnockOnWood]

Or actually, skip the plastic entirely.
Insulate with, for example, cellulose, which can handle moisture transport.
And boards/paneling that can manage a little moisture transport.