I am in the process of renovating my kitchen. I removed everything down to the studs. One of my bathrooms backs up to my kitchen. Once I opened up the wall behind my bathroom shower stall (a fiberglass one piece tub and surround), I see that there is no insulation, drywall, or cement board around my shower stall. It is just sitting in the open on the other side of my kitchen studs.
The bathroom is a small 3 fixture bathroom that has 1 exterior wall. This exterior wall is about 10’ long and the foot end of the tub is on the exterior wall. From what I can see, there is no insulation in this exterior wall. This bathroom was remodeled about 20 years ago and they added this stall. I think they removed the insulation only in this area–not the entire length of the wall.
This stall does not go all the way to the ceiling so it has drywall from around the top of the shower to the ceiling. Is it possible to put some type of insulation in this void around the stall? I have often said that this bathroom didn't feel as though is was insulated. It is always cold in this bathroom in the winter.
I do not want to tear out the shower stall at this point, but am hoping to be able to do something with the access that I have from my open kitchen walls. I do not know anything about vapor barriers or appropriate types of insulation for this situation.
Best Answer
There are two issues: 1) yes, you should add insulation, and 2) no, it should not have a vapor barrier.
1) Yes, insulation will help with the temperature comfort level you’re complaining about. It will help to maintain a constant temperature.
It will be difficult to install because it’s not very accessible.
2) A vapor barrier should not be installed.
Most people don’t understand that “vapor” moves both ways through a wall. That is to say, vapor moves from the warm side to the cool side. As the seasons change, vapor will move through the wall reaching its Dew Point, and turning from a vapor to a solid (water).
If this water is trapped in the wall, it could create dryrot or mold. With a vapor barrier, vapor will enter the wall but not be able to escape. In fact, poly sheeting can accelerate the problem and is no longer recommend, except in the coldest year-around climates.
Here’s an article that explains it better:
https://www.energyvanguard.com/blog/75130/What-Happens-When-You-Put-a-Plastic-Vapor-Barrier-in-Your-Wall
It’s very important to understand this concept for bathrooms with excessive moisture. That moisture needs a way to escape from the wall. (Even the best installed poly sheeting will allow vapor into the wall around outlets, joints in sheeting, top and bottom plates, etc. )