Re: Is it cheaper to leave your heating on?

[Simon Haslam <simon_haslam@xxxxxxxxxxx>]

Yes, that bloke in the Sunday Telegraph is always going on about
condensation in walls reducing the insulation value though I'm not too
convinced myself.

I personally don't run my heating 24/7 but one factor in its favour is that
the heat requirement from the boiler should be relatively lower. Assuming
it's a condensing gas (or presumably oil too) boiler that means it will be
able to run with a lower flow temperature, giving lower return temperature,
hence more condensing. Despite what is written condensing is not a
"does/doesn't" action overall - the lower the return temperature
the better (have a look at the boiler output vs gas input charts). My
understanding is that the more efficiently your condensing boiler is
running the less steam you'll get in the flue (since more water is going
down the drain). This is also why you can get energy savings from weather
compensation controls - it lowers the boiler flow temperature according to
the weather/heat requirement. I wonder whether most central heating
systems, even newer ones, are designed to minimise return temperatures
though.

Certainly heat loss being proportional to temperature differential suggest
maintaining a, say, 15 degree inside-to-outside
difference when no-one is there compared to letting it fall to, say, a 10
degree difference doesn't make sense to me, but as Tim says there are lots
of considerations (a modern, highly insulated house with underfloor heating
throughout could well be be more efficient and comfortable with low level
heating on 24/7 - a passiv-haus might not need much heating at all).


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