Some years ago, I insulated the cast iron bathtub in my own home with six can of Great Stuff foaming insulation. Recently, I used the bathtub in the Goldsboro home, which is 30 years older than mine. Although the tub is deeper than the one in my house, it didn’t hold the heat at all, and the bath was not as enjoyable as it could have been.
I decided to insulate this tub as well. We bought six cans of Great Stuff Big Gap filler–I wanted all the fill power I could get. I’m not worried about the insulation expanding too much; there’s plenty of room under the house and the tub will not lose to the foam.
We have disposable gloves on hand. It is not possible to use foaming insulation without getting it on your hands; gloves make it less problematic.
I have worked with overhead foam before. Cover your hair, and wear clothing that can get ruined. (One day, I’ll write up my experiment with an exploding balloon of insulation foam… for now, trust me to know, “bomb voids” are for real.)
I needed better light than a flashlight could give me. We do not have outdoor electricity in this home, so I had to run a cord from the bathroom.
John helped. That’s an underwriter’s knot keeping the two cords together.
Hurricane Matthew took the furnace that’s just to the left of this picture; part of the repair work gave us a new access door to the crawlspace. (The HVAC team had to replace some of the ductwork that took on water. Strictly speaking, what we suffered was rain damage, when 18″ of rain fell onto mostly flat land faster than it could flow away to the river. The water rose into the furnace. This is not good for a furnace.)
Looking into the crawlspace under the bathtub. The white pipe at the left attaches to the bathtub drain. Most of the house is drained with black iron pipe.
I shot one can of Great Stuff directly under the tub, by inserting the tube into the gap between the subfloor and the bathtub at the drain, shooting towards the long end of the tub. I am hopeful that this foam will do the bulk of the work, sealing the cast iron from the outside-temperature air and helping to keep hot water hot.
Sounding the tub from the inside shows that there is respectable coverage, with dull thuds where the foam reached and more of a ringing sound where the tub has not yet been foamed.
There are three cutouts in the subfloor below the tub. They show that there’s a pretty big space to fill between the tub and the wall.
The hooks in this picture are from the worklight.
I really didn’t want to have to use as much Great Stuff as it might take to completely fill a gap this size. (The one at the back of the tub, where it slopes, is even wider.) Unfortunately, Great Stuff will fall with gravity, so I couldn’t simply shoot it along the wall of the tub and trust that enough would stick to make a difference.
For three weeks, I collected “filler”–any clean recycling that was light weight, narrow enough to fit through the hole in the subfloor, and not attractive to bugs.
I used all of the material in the larger of these two bags in one side of the tub, tossing cans and jars into the space, and then shooting a can of foam over them until the can ran out.
At that point, I was noticing the off-gassing fumes, so I stopped. I need to collect more material to fill the other side of the tub, as well as the back. When I worked on my own house, I used 25+ cans of insulation* to seal the sill plate, and I remember my face breaking out and suffering bad headaches if I used too many cans at one time. This project has waited 80 years. A few more weeks won’t make any difference.
*the price difference between using individual cans and buying a bulk tank of foam was not substantial. Using individual cans solved cleanup problems, and let me break the work up into smaller units. I could spray three or four cans and come back without having to take a lot of time cleaning up the spray nozzle so it didn’t clog.
A few weeks and one ice event later, I returned to finish the project. I had collected more filler material.
I tossed as many cans into the open space between the sides of the tub (this is the finished both-sides part of the bathtub), and then shot a can of Great Stuff over everything. It was a painful stretch, to get the nozzle as far into the gap, along the inside of the tub, as I could. Eventually, the foam started dripping out of the gap and I stopped up the gap with a yogurt container lid (not before a big dollop landed on my neck).
The gap between the tub and the house was much bigger at the back end of the tub, so I tossed cans and yogurt containers into the space, and then shot another can of Great Stuff over everything. I stuffed two more drink cans into the space as the foam started oozing backwards.
I used the last can on the other access port, aiming toward the back of the tub. On the inside of the house, knocking on the tub gives a solid thud rather than the former metallic ring, pretty much everywhere.
There’s no way around it. Great Stuff is messy. I tossed the cans and gloves into a paper sack so they could set up and harden out of the way of the dogs, and not get stuck to the sides of the Zarn cart.
I think it’s time to call this sweatshirt “dead.” I have two stained sweatshirts waiting to move into the “yardwork only” category. I don’t need to try to resuscitate this one.
It took about three days and a haircut to get all the Great Stuff off me.