"Cameron" wrote in message
Efficiency
- the target temp is a room air temp of 19oC - 21oC
- i'd assumed (ASS of U and Me) that the more of the waste heat (the
return boiler tempurature) used, the more efficient the boiler?

Heat will alway seek out the cooler areas and try to reach equilibrium. The
higher the differential, the faster the heat will move. The air will absorb
heat from the radiators and once the air reaches the temperature set on the
thermostat, the circulator turns off. Any heat put into the water is going
to be given up in the house. It may be in the feed pipes or return pipes,
it may be in the room that you want to heat or another room, but all the
heat generated and put to the water will be in the house. Essentially, it
is 100% efficient from the water.

While heating the water, some energy is lost up the chimney. If 20% goes up
the dhimney, the heater is 80% efficient. With carbon based fuel, products
of combustion myst be vented up the chimney so no heater will ever be 100%
efficient.



Boiler Size
Put it in myself 6 years ago - 95btu combi - way obversized for heating
a 2 bed bungalow - but I wanted to fill a bath!
Other than the quality of the thing, I have no complaints - a combi
fan!

Oversized will cycle shorter time. May be some efficiency loss from
constant starting. but toher can better answer that.


Insulation
200mm Loft - no walll - new extension will be to building regs

Look into putting some in the walls. Major savings to be had.


"Hydrotherm Hydropulse boiler" wow! sounds like some body enema
device!


Can I "please" rephrase my question

What would you do?

About what? Oh, heating hte new addition? I'd add some cast iron
baseboard.