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Insulating a Bathtub: How-To with Photos

Updated on April 15, 2016
Maren Morgan M-T profile image

Maren is a one-person fixer of "TLC Needed" houses. She explains methods simply to homeowners who are not in the construction trades.

No Wonder the Bathwater Cools Quickly

Look at the underside of this bathtub - nothing but air from uninsulated walls and floor.
Look at the underside of this bathtub - nothing but air from uninsulated walls and floor. | Source

Problem: Bath water rapidly drops in temperature

If I weren't ripping my house and bathroom apart for other reasons, I probably would not address the situation of an un-insulated bathtub. However, since I am tearing the bathroom (and adjoining rooms) down to the studs, this is a great opportunity to remedy a pet bathtub peeve of mine.

Maybe in generations before me, a bather did not stay and soak in a tub long enough to feel it chill down, but I doubt that. Perhaps in those days when we were not as conscious about the lim ted resources of the earth, about saving energy and money, people could heat their bath rooms to steam room heights for as long as they wished. But now we are in "today," and many of us living with old tubs that allow heat to escape.

Although I am more of a shower-er than a bath-er, there are times when I want to soak. One instance in particular is after an afternoon of sled riding. I want to be able to warm myself up in a hot tub. Other times, a family member needs to be able to soak a body part (for example, sore back, tukas, leg) for medical reasons. Wouldn't it be good to have the water temperature comfortable the entire time? Thus, we come to HOW to insulate that tub!

Bathtub Insulating Supplies

  • Whatever tools you need to open up the wall(s) touching the tub
  • Whatever supplies you need to close those walls afterwards
  • Work gloves to protect your hands
  • Face mask and googles for the same reasons
  • Utility knife
  • Optional: bubble wrap packaging
  • Fiberglass insulation rolls, unfaced or faced
  • A 3 to 4 foot long sturdy pole, such as a broom handle or a vacuum cleaner pole

Insulating Materials

A utility knife rests on a "Pink Panther" fiberglass insualtion roll.
A utility knife rests on a "Pink Panther" fiberglass insualtion roll. | Source
Common packaging bubble wrap.
Common packaging bubble wrap. | Source
More common packaging bubble wrap.
More common packaging bubble wrap. | Source

Find the trouble spots

I had removed all the layers of my bathroom walls anyway and learned that there was absolutely NO insulation in either exterior or interior walls. In my house the tub sits along an exterior wall. One end rests against an adjoining bedroom. The faucet end rests against a tiny closet in the bathroom. In addition, I have a partial view of underneath the tub from my unfinished basement. At the point where plumbing pipes go through the floor, there is a hole through which I can further ascertain the un-insulatedness of the tub. (Sigh...)

By cutting into each side wall, I was able to crack open the wall enough to see that my tub unit has vertical side walls which are absolutely empty, "unfilled" and available for insulation.

The Spots Waiting for Insulation

A "naked" tub end.  Look at all that air space greedily clamoring to steal the heat from the tub water!
A "naked" tub end. Look at all that air space greedily clamoring to steal the heat from the tub water! | Source
A more distant view.  One can see where the interior wall insulation ends and then: nothing.  No insulation.
A more distant view. One can see where the interior wall insulation ends and then: nothing. No insulation. | Source

The Procedure

(Ok. I decided that I did not want to lift the tub unit up to put insulation along the exterior wall and underneath it. Nonetheless, that is an option for the strong and hardy among you.)

I had read that even common packaging bubble wrap will perform heat insulating, so I gathered up what I had in the house. I figured that those pieces would be easier to stuff into small spaces. So, I shoved them towards the back, exterior wall which I could not reach. Then, I used a broom handle to further shove them into place.

After that, I used my tape measure to roughly estimate the length pieces of roll insulation to be place around each tub end. Then, I cut those lengths with my utility knife and place them inside. The broom stick was again used to help push and position insulation.

Plenty of Potential Space to Insulate

Diagram of tub.
Diagram of tub. | Source

Easy

As I positioned and pushed the insulation around the bathtub, I was pleased to find that it stayed in place. I think that this is because the space is tight to begin with and that the insulation naturally expands a little. One should not cram in so much that the insulation cannot expand. If that happens, it is less effective. Insulation is designed to have copious little air spaces.

Wrap the Tub with Insulation

A roll of fiberglass insulation around a tub end.
A roll of fiberglass insulation around a tub end. | Source
Another view of  roll insulation around a bathtub end.
Another view of roll insulation around a bathtub end. | Source

A Few Words about Insulation Type

I used rolls because this was a DIY project. Faced insulation (it has paper on one side) is NOT needed, but you can see from my photos that this is what I used. The reason is that my local big box hardware stores do not carry much unfaced insulation. Another option for people who have the correct equipment is blow-in insulation. That was beyond my experience at that time and, in my unschooled mind, too dangerous for me to attempt.

Finished Tub Insulation

This is a great improvement over a cold bathtub.
This is a great improvement over a cold bathtub. | Source

Close the Walls

For me, cardboard, plywood and white duct tape are holding the air inside the two walls I opened. That is because more work is scheduled for the bathroom closet and for the adjoining bedroom. However, if you are completely done working on the areas you needed to open, do what you wish to close the wall holes.

Enjoy

The next tub bath is going to rock!

Photos and text copyright 2013 Maren E. Morgan.

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      Michael Bourke 3 months ago

      Would we have to worry about condensation getting the insulation wet, since there is a big temperature difference between the hot water (thus tub), and the indoor temperature?

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