Insulation Missing Behind Bathtub

[AllanJ]

1. I noticed that my bathtub is really cold in winter and I suspect there is no insulation in the outside wall against which it is installed.

2. I saw a "This Old House" TV episode showing "them" installing a bathtub before the insulation guys came.

Seeing that the escutcheons for the tub faucets, etc. do not make an absolutely airtight seal, is it really undesirable to insulate the space behind and under a bathtub for fear moisture could accumulate?

Also I am seeking advice on the best way on correcting the situation: Drill small holes in the exterior wall and squirt in expanding foam? Would I get a uniform fill? Would the vapors emitted as the foam dried warp the (fiberglass) tub? Cut large holes in the exterior wall and blow in cellulose? Would it slowly settle under the tub require a repeat performance? Would it slowly settle under the tub exacerbating moisture problems?

[Bumblerazz]

If going to use foam do not use the expanding foam type. It has unexpected destructive powers if not blown in properly (collapsed an icebox I was installing on a boat).

I've used iceyene (sp?) on a similar problem. Worked great to seal and insulate. R value for the stuff ain't great, R5/inch I believe, but it is not affected by moisture and will seal any air holes (also insects don't like to chew on it!!). It is also very easy to cut and shave if it overflows in unexpected areas. Problem is, I don't think it can be blown in through small holes, the area to be sprayed has to be accessible for best results.

I've also used blown in cellulose, but only small areas. As you say, it settles and packs, it is not moisture resistant (to any significant degree) and won't seal any air holes.