Mold proff Insulation around Tub

Which is the best insulation to use around a bath tub which is
resistant to mold growth ? (for remodel tub install)

Thanks, Ron

That’s an interesting question. I look forward to the responses, of which mine is not one.


I’m not sure why you want insulation around the tub. Are you talking about in the wall behind the tub or in the actual cavity under the steel of the tub?

In general terms mold will grow on just about any surface that remains wet for long periods of time. Organic particles in the air will land on the wet surface and “stick” there as food for the mold to grow.

Having said that, moisture resistance insulation, insulation which does not loose its insulating value when it gets wet, would include mineral wool and most foamed plastics (ie spray foam, XPS, XTPS, etc). There are some others. If you are insulating around pipes and other components that may need future servicing the mineral wool may an option to look at.

Do not use fiberglass (loose fill or batts) or cellulose as these loose their R value when they get wet and all you’ll have is a big mess.