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 exchanger.
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?