I am planning a work-shed. Garden office, if you prefer.
Fully insulated for year-round use.
I'm looking at 2m x 4m (ish) floor plan and 2m walls.
90mm thick Celotex on walls and ceiling, and as much
as we can squeeze in on the floor.
My back of an envelope calculation is that a perfect
Celotex box of those dimensions needs 250W to maintain
a 25 degree temperature differential. IOW in theory
one person and a computer can stay comfortable when
it's zero degrees outside.
Obv., nothing is perfect, and there will be a number
of double-glazed windows and doors.
But I figure a fairly low-power heater would be sufficient.
However... my eyes were caught by various offerings of
evaporative coolers at ~70 quid. And I thought it
might be nice to have a cool office on those few days
of the year that it actually gets hot.
But it turns out that by most accounts, those things
are useless. OTOH for a bit more wodge one can get
a proper real air conditioner, albeit one where you need
to pipe hot air out of a window, using a pipe and a
(supplied) blanking plate. And then in the winter
you can turn the thing round and use it as a heater.
But then for a bit bit more wodge, you can get a real
proper wall-mount air conditioner with external heat
The big attraction is that these things can (allegedly)
operate in reverse, so that you can get ~3kW of heating
for ~1kW of input. Which could, in the long term, save
quite a lot of money.
So... has anyone got any experience of this sort of thing?
What's the *realistic*
cost of heating a shed-like-this
over the winter months? Can a heat pump (i.e. air conditioner
in reverse) work in sub-zero temperatures? Won't it just
ice up horribly?