michael adams wrote:
"Easynews" wrote in message
...

Hi Michael, yes, I know what I want to use the greenhouse for- as for the
cost of running, it is a hobby, hence does not have to be profitable or
particularly cost-effective- and there shouldn't be much difference in the
running cost of heaters with the same power rating (or correct me if I'm
wrong there?) The temperature I want is based on what is comfortable to
work
in for long(ish) periods, rather than what is going to be grown,

NB You only really need that temperature in the daytime then... and it
would be a lot more cost effective to run in at 5C and wear an extra
layer of clothes. Or work in the greenhouse only on nice sunny winters
days when 10-15C is likely inside.

safe temperature for some insects that are more used to the Mediterranean.
There is also the option of just heating one part of the greenhouse, which
has a partition - but I need some help choosing a heater / type of heater.

Unless you really do need something special with a large slow fan or
huge power consumption I found the cheapest 3kW one operated with a
remote thermostat to be perfectly adequate fro a 10'x10' warm end of a
10'x20' greenhouse.

Frostshield 3kW fan heater with thermostat costs £50; a Bio Nevada 3kW fan
heater (with a thermostat & tube) costs £260. A Camplex 3kW fan heater
with
thermostat costs £120. Apart from the shape I'm having trouble seeing the
benefits / disadvantages.

A one minute Google reveals that the the Bio Green Nevada incorporates
an air re-circulation system which is claimed to save up to 50% of energy
costs, whereas the Frostshield is a straightforward common-or-garden fan
heater.

I would take all such energy saving claims with a huge pinch of salt.
The main losses from a greenhouse are leaks and drafts (or essential
ventilation for gas or kerosene burners) and conduction/convection
through the glass windows. Twinwall insulated polycarbonate gives a
worthwhile improvement in thermal insulation as does much cheaper
bubble wrap.

Regards,
Martin Brown