Greenhouse insulation

[Colin Miles]

Pondering the merits of heating a greenhouse I am wondering also about insulation. In particular looking at the bubble-wrap heatsheets that the likes of Two Wests sell. Has anyone any experience of them? What sort of difference do they make to heating costs? Are they easy to fix and unfix? I can imagine that in March they might well help by a combination keeping the cold out and preventing overheating - or do they? When do you take them down?

[Geoff]

When I bought my Hartley Wisley 8x10 in February 1995 I decided to insulate and heat it. These greenhouses have a roof with two angled panels rather than one. The ridge is aligned East-West and I insulated the North Wall, both the North roof panels, the upper South roof panel and both ends with bubble wrap. I bought a UV grade from LBS, not sure if their prices are as good as they were but I go to the site which gives a discount. Many alloy greenhouses have a special channel you can twist clips into to hold bubble wrap which must be easy but the Wisley only has a groove that you can put self tapping screws into, because of this I decided to put the insulation in permanently with drilled plastic discs and stainless self tappers to hold it in place. Also this side of the greenhouse has permanent gravel filled staging so removing it each year would be a pain. For the South wall and the lower South roof panel I made removable panels out of Correx (like translucent corrugated cardboard, I think it is polypropylene) held in place with strips of aluminium and self tappers into the same grooves. On this side I have easily removable wooden staging. The greenhouse has a concrete floor incorporating polystyrene like the floor of a house. When the tomatoes are ready to go into gro-bags I remove the wooden staging and the Correx panels to maximize the light.
You ask how much it takes to run it / how much insulation saves. Unfortunately I don’t know but I have started measuring it. I read my meter regularly in December to get a Winter base load, I now have just the propagator running so I am hoping to spot what difference that makes then when I start up the greenhouse heating I’ll check that as well.
I have replaced the bubble wrap once and I think I shall have to replace it next year so you should be able to get 6 or 7 years out of it (I think the second lot is not lasting as well as the first did). I hope the picture clarifies my description - you are looking West, North to the right. I wouldn’t be without heat in the greenhouse – I would give up lots of other things first.

[Colin Miles]

Thanks Geoff! When I visited my local gardening shop they had the heaters and bubble-wrap there and also sell paraffin, so I decided to go ahead - well with a midi heater which is a little on the small side, but am hoping the bubble-wrap, which I intend to put on the northish side will help overcome that.

[Tigger]

If you've got a local farm suppliers or builders, you'll find rolls of bubble wrap much cheaper there.

[Brooklynodog]

I use the bubble wrap, but find I only get a couple of years out of it as it perishes in the sun and goes brittle

[Geoff]

You must get uv grade.