On Mon, 30 May 2011 10:20:59 +0100, The Natural Philosopher wrote:

Hot air systems are very very good at getting a space up to temperature
quickly with very few hot spots.

But unless all the rooms are conveniently arranged directly around the WA
unit there may be permanently cold spots. Some otherwise very nice 60s
Modern flats round here have the unheated bathrooms because they don't
adjoin the WA units!

They also are compact.

Er, eh?! A full-size cupboard devoted to the WA unit and ducting compared
to a suitcase-sized gas boiler? Plus a HW cylinder and storage tank
because you don't get 'combi' WA units.

Their efficiency and cost depends on how they are driven..

The gas-fired units I've seen have permanent pilot lights on both the
main WA unit and the separate water heater part, hence dinosaur levels of
efficiency. I'd guess newer models might get up to standard efficiency.
Do they even make high-efficiency (condensing) models?

--
John Stumbles -- http://yaph.co.uk

It's bad luck to be superstitious.