Don't worry about it.

We have had 2 contractors tell us that we need special insulation, so I am worried about it. Has anyone done this that lives in a semi-cold climate?

Thanks alina_1, I have had these same discussions and worries. The contractor I am using said there is special insulation that can be used for that wall, however, speaking with a friend (contractor) in another state, he said that it's all about how that insulation is used that makes or breaks its effectiveness. I am using a rainshower from the ceiling and a handheld shower on a bar on the the one interior wall. The shower will be about 40 inches deep, so I am thinking of putting 2 tall and narrow niches on both sides of the valves. Not sure how that will look. Do you have pics of yours? Or does anyone else out there have pics to show?

I'm in CT, so I'm a bit north of you.

Niches are typically sized to fit in a 2x4 stud wall. If you have 2x6 stud exterior walls, then use a sheet of 2" thick rigid foam board in the stud bay right up against the exterior sheathing.

My first choice is polyisocyanurate insulation, its about R-6 per inch. That would give you R12 between the niche and the sheathing. Second choice would be extruded polystyrene, or XPS. That's about R5 per inch for a total of R10. Note that the second one is extruded polystyrene, not expanded polystyrene. Big difference between the two.

You can also use a sheet of 1" thick foam and just double it up to get your 2" thickness. They come in 4' by 8' sheets, so the 1" thick sheet doubled up might result in less waste for you.

Then you can fill the remainder of the stud bay with whatever insulation you are using in the rest of the wall; FG batts, cellulose, etc.

Doba,

I live in a very mild climate, the PNW, where it very rarely freezes, certainly never as cold as Washington, DC. We are almost finished our Master BR, and NO we didn't and wouldn't put a niche on an exterior wall.

We dealt with niches, (which I love, can't believe I ever survived without them...LOL), in two different ways in the two BR's we've renovated so far.

IN our basement guest bath, we built a shelf on top of the foundation walls, so in essence we have a four foot niche...love it! The original BR just framed in the exterior wall straight up from the foundation hiding/wasting about 8" of space, so when we gutted the BR, we moved back the upper wall and gained shelf space, we continued it all along the whole length of the 10 foot wall, this pic shows the 4 foot shower section before we put up the glass walls.

In our Master BR, we built out the one interior wall the width of a 2 X 4, ie 3 1/2" which turned out 4" wide with the thickness of thinset and tile added. DH then cut the existing 2 X 4 by half and routed the copper pipe for the shower head in the space left, and built the niche into the cut out space of the 2 x 4's, with the thickness of the cement board, the thinset and the limestone mosaic, the inside dimensions of the niche are 5" deep, and with the granite overhang the bottom shelf is a little over 5 1/2" deep.

HTH