Insulation in the bedroom

[coff33NMilk]

My sister finally moved out of our parents' house last week, but I’m still feeling worried, especially about her place

She shares a house with two of her friends. I checked there yesterday, her bedroom is the type that’s cold in the winter and hot in the summer. I found out that two interior walls don’t have any insulation in them, so I decided to insulate using pink foam and think about a vapor barrier.

One drywall shared with the bathroom and another with her friend’s bedroom.
What do you guys think about the vapor ? is it a good idea or a no no? need advice guys!

 

[guvnur.jake]

Skip the vapor barrier on interior walls, you'll just trap moisture where it doesn't belong. Pink foam (assuming you mean fiberglass batts) is fine for sound and thermal comfort between rooms. The bathroom wall might need different thinking though

 

[purdil21]

My sister finally moved out of our parents' house last week, but I’m still feeling worried, especially about her place

She shares a house with two of her friends. I checked there yesterday, her bedroom is the type that’s cold in the winter and hot in the summer. I found out that two interior walls don’t have any insulation in them, so I decided to insulate using pink foam and think about a vapor barrier.

One drywall shared with the bathroom and another with her friend’s bedroom.
What do you guys think about the vapor ? is it a good idea or a no no? need advice guys!

For the bathroom wall specifically, you might want to be more careful since moisture is involved. What's the wall construction like now? Is the drywall in good shape?