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Best Insulating Method for Bathroom with Outside Walls

cohnaudio's picture


I currently have a bathroom with two outside 2alls and a vaulted ceiling. The bathroom is unbelievably cold in the winter. I am going to be redoing the bathroom and was wondering what is the warmest insulation I can use in a boathroom - i.e. taking into account the greater moisture. I was thinking blown in foam (closed cell?) would be the best for stopping drafts, but I was concerned about the moisture (I live in Westchester, N.T.). I suppose the other option in seal with closed cell to seal up leaks and put in rigid, which I understand has a higher R value. Would I put up a plastic vapor barrier in that case? Would you use the same type of insuraltion in the walls of the shower (which also get very cold because the other side is open to a stairway that gets very cold. any tips would be very much appreciated.

There is no better insulation (post #183651, reply #1 of 6)

There is no better insulation for a wet environment that sprayed foam. It also serves as its' own moisture barrier.

The short version is: strip your walls bare and have a pro do it. Then close up the walls. That's as simple as it gets.

Another part of your problem is that cathedral ceiling. Nice for evacuating moisture, lousy for keeping the heat near the floor.

In a bath, there are few things nicer than a warm floor. Perhaps adding a radiant may under your floor is a perfect solution.

Absent that, you can 'cheat' by putting a heat lamp in the ceiling, and letting it warm the floor while you shower.

thanks. I figured sprayed (post #183651, reply #2 of 6)

thanks. I figured sprayed foam would be the way to go. Should it be open or closed cell? The closed cell I assume will not let moisture pass through either way. Will that create a situation for mold on the inside of the wall board?

I think putting water heated radiant is going to be difficult, so I may explore electric - though not as efficient, nice in the morning.

We have R-21 sprayed closed (post #183651, reply #3 of 6)

We have R-21 sprayed closed cell foam - no mold problems.

Jeff,   Did you also put (post #183651, reply #4 of 6)



Did you also put up a vapor barrier?  I would think that would not be advisable - to allow moisture transfer.



With closed-cell you don't (post #183651, reply #5 of 6)

With closed-cell you don't need, or want, a second vapor barrier/retarder. Closed-cell itself is both a vapor and air barrier and has, in general, the highest R-value per inch. About R6.5 per inch.

I'll rephrase  a bit and just say that you never want more than one vapor barrier in any wall assembly.

With open-cell you would want a vapor retarder/barrier. Open-cell is an air infiltration barrier, but not a vapor barrier. Open-cell also has a lower R-value per inch, about half that of closed-cell.

Closed-cell has a density of about 2 lbs/cuft, open cell is about a quarter of that, 0.5 lbs/cuft. You might seen them referred to as "two-pound foam" or "half-pound foam".

You'll often see people argue that open is better than closed because it's less expensive. Well, it is less expensive, but it's also half the insulative value, and if needed, you'll incur additional expense installing a vapor barrier with open that you don;t need with closed.

Just a few more ideas.

There are 10 kinds of people in this world; those who understand binary and those who do not.

What Mongo said. (post #183651, reply #6 of 6)

What Mongo said.