Insulating an acrylic bathtub
SwissCarpenter
| Posted in Construction Techniques on
I’ve heard of some plumbers filling the interior voids of actylic bathtubs with either fiberglass insulation and/or spray foam insulation prior to installation. It sounds like a good idea to retain heat in the tub. Has anyone done that and is there any downside? I assume low expanding foam is the way to go to prevent bulging or cracking of the acrylic but I’m curious as to other people’s experices and techniques.
Replies
school of hard knocks
Let me help you with that...This summer did a total rehab. Installed a new acrylic tub (and surround with 30# felt, then durock, then latex waterproofing, then subway tile). Looks GREAT.
I read up and saw the caveats/cautions about insulating, but wanted to preserve warmth. I braced the edges and sides, filled most of the cavity with EPS (white styrofoam) and went to town with minimally expanding foam, just to fill up the voids. It looked like it all stayed in position.
Except, when I laid the floor the next day (maple 3/4 t&g), lo and behold, the damn thing had sprung out in the middle, about 1".
First, the fix: Laying on my side, I spent THREE hours drilling, chiseling, scraping, CUSSING, to get all the foam chipped away and removed, little bit by little bit. Fortunately, I had an okay access by the plumbing. It was easy going the first 18"-24", but then, weirdly, it got really hard. I ended up with a 30" crosscut saw just shaving off layer after little layer. This was NOT fun.
How did this happen?Apparently, the little 6" block of foam that came from the factory, that was attached in the middle of the tub to keep the front apron relatively in place and the right distance from the "bowl," had a really weird chemical reaction with the expanding spray foam and it turned into a sticky, but hard, and massively expanded blob. And some of that happened 12 hours or so after I removed the bracing (and the other foam had long ago cured up and I thought I was safe).
So, when all was said and done, I lost a few pounds of sweat, I restored the tub to it's proper shape, and I filled the cavities with Roxul (rodent resistant mineral wool)
My wife just took a bath and said it was wonderful.
Please, don't use foam.
My impression was that the foam was to prevent the "drum" effect of the relatively flimsy acrylic. Acrylic is a better insuator than cast iron and shouldn't really need "insulation" to speak of.
The wonderful software did it to me
Hung when I pressed "Post", so I pressed it again.
Similar experience as user.
Even 'low expansion' will move the tub, low does not mean zero and there is a hugh surface are being pushed on.
Our custom 6 foot tub moved enough so it would not drain properly, left a puddle at back of tub.
Like user, spent a few hours with an old 6 ft long crosscut saw getting the foam out from under the tub.
Forget trying to use any spray in foam would be my advice.
Enough said
Damn. Excellent advice guys. Looks like I'll be saving a few $$ by not buying any expanding foam!
well then
I feel a bit less stupid if a wise expert like junkhound also had this happen. Funny that we both ended up using saws to fix this...