In article ,
Andrew Gabriel wrote:

Considering the bottoms of most baths are boxed in with panelling
I just don't believe there is any significant heat loss from them
compared with the wide open top.

We used to have an iron/steel bath in our icy
cold dormer house in Cheltenham. I do have to
say that, when sitting in it in winter, your
bum was the first thing to feel the reducing
temperature. In that warm air heated? house
I regularly pondered the technical problems
of a) heating the bog seat, and b) heating
the underside of the bath.

--
Tony Williams.