In article ,
The Natural Philosopher writes:
John wrote:
Can anyone give me a quick idea on the BTU requirements for a radiator for a
bathroom - approx 2metres square. insulated ceiling - 1920's walls - double
glazed window.

About 500W.

I calculated 875W for a bathroom 1.2m x 2.4m, 9" brick walls
(two external), insulated ceiling, small double glazed window,
using the Myson calculator. In practice, the Myson calculator
seems to have over estimated throughout the whole house (it
was a beta version), although that has meant I can run the
boiler at only 45C once house has warmed up, making the
condensing boiler very efficient, so I'm not complaining.

--
Andrew Gabriel