keith ;-) wrote:

Hi Martin,You presume right! I am keeping my 10 x 8 greenhouse to around 15c
24/7 for growing orchids.The greenhouse is green aluminium ,I have put 4 ft
close board fence panals around the out side so the bottom half is clad &
inside has bubble wrap ,apart from the double door end.

OK. That is a mistake you need to insulate the double door as well.
Hanging a curtain of bubble wrap on the inside to stop drafts and so
that you don't let too much hot air out when you open the doors will
help. I had an internal door in mine with the hot end half heated.

You roughly double the heating bill for every 5C above ambient.

I will have to insulate between the cladding & glass.And think of a way of
insulating the double door end(two 2 ft wide sliding doors)with 2ft glass
panes either side.

For the outside if you can stand it being opaque and not especially
pretty B&Q do cheap 2" & 4" polystyrene slabs that stand up to the
weather well and have superb isulation properites.

This is my first winter with the greenhouse so its a learning curve!
Its an expensive hobby.

Orchids certainly are!

I grow mainly cacti so I can get away with frost free except for a few
of the touchy exotics and they spend winter either in a hot box or
indoors. You should be able to get the bill down a bit.

Cacti never really liked paraffin heaters the condensation tends to
encourage fungi on dormant plants. I guess orchids would love it!

Regards,
Martin Brown