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Mike W 123
insulation advice needed

I have an old Adirondack camp and am in the midst of a Bathroom remodel (original install was 1973). The exterior walls are all 2x4 studs and I am looking right at the backside of the exterior wood siding once the sheetrock and old insulation is removed. What is the best way for me to insulate this bathroom with such a thin cavity available to me?

thanks for your help!

Re: insulation advice needed

Closed-cell foam is ideal for this. Second best is fibergalss batts (facing to the inside) with a plastic vapor barrier on the inside over them. The foam will be a contracted job because of the equipment and skills needed, the fiberglass can be DIY and in this small of an area should be DIY if you go that way. Remember to use the correct type of sheetrock, the regular stuff is not moisture resistant and will fail quickly in a humid bathroom. I like seeing it everywhere in a bath even though codes here do not require that- it's cheap insurance against possible future moisture problems. If you really want better insulation then furr out the walls or stagger-stud them to add thickness but really I think that's overkill unless the rest of the house is up to that standard.


Re: insulation advice needed

If you are tiling your shower or tub surround you do not want a vapor barrier over the insulation behind any shower waterproofing. A small 6 inch overlap is OK, but you don't want a moisture sandwich. The shower waterproofing provides the insulation vapor barrier

Re: insulation advice needed

If you have the space, I would first get some Timbor and mix it with water or an antifreeze water mix and treat the wood. You can use a product called Boracare if you don't want to do all the mixing yourself, but it costs a lot more. That will stop rot, mold, and insects (termites) from getting into the wood. The install unfaced fiberglass batts with any gap to the outside wall, not the interior side. In fact, leave it slightly proud of the studs to the inside.

Next, cover the studs with a 1/2" thick, 4x8 foil faced foam board panels. That may not seem like much but it breaks the conduction between the inside wall surface and the outside wall surface through the studs. For the wall sections that are not behind a tiled shower, tape the seams with a foil tape. Behind a tiled shower, leave the seams open for the reasons in the earlier post.

Then sheet rock or cement board as appropriate and finish.

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