In article ,
"IMM" writes:
Very few boilers have insulation around the heat exchangers.

Keston does. However, that might be more to prevent frying
the electrics inside the boiler casing, as most of the heat
which escapes from the heat exchanger into the boiler case
would simply serve to preheat the combustion air, since the
case is vented only out through the combustion chamber. Thus
the heat would not be lost -- it cleverly goes back into the
combustion chanber. The front of the casing does get a bit
warm just round the heat exchanger, so a little is lost that
way.

One figure Keston don't give is the heat input to the room
from the boiler casing, which would have been useful to know
when I originally did all the heating calculations (some other
manufacturers do). I just ignored it, and that doesn't seem to
have caused any great error in that room, so it's probably not
a lot.

--
Andrew Gabriel