Overnight lows

[Sean Kemball]

What do you do to manage temperature in your greenhouse?

My greenhouse was almost too hot to grow in at the height of summer - even with all the doors and windows open it was heading towards 40 deg. However, now it's winter I have the opposite problem.

This is the temperature yesterday morning - 2 and a bit degrees! And I'm in sunny Auckland. I have tomatoes in there and they are (amazingly) starting to flower. Not sure they will survive if the temp swings between 2 and 20 (which it gets to on a good sunny day) though. The bell pepper plant I rescued from the chilly garden seems to like things, it's fruiting. And the chilis are doing OK, but all they have to do is survive.

- I've tried burning candles under terracotta pots, which probably lifts things by a degree or so at most, and is very localised in effect.

- I've also put fruit juice bottles full of water around the planter boxes, for thermal mass. Not sure if that's making a difference, to be honest. 

- I'm looking for lots of cheap bubblewrap so I can insulate the roof. 

- And I am thinking about rigging up some sort of solar thermal system (once I finish building my chicken coop, and if I can find cheap bits to do it with). Not absolutely sure what I'm doing with this though, but hey, how hard can it be? :)

Any other ideas for very cost-effective greenhouse heating?

[Rana]

After all the inquiries I've made, Ive come to the conclusion the only cost effective way is to share the greenhouse somehow with your home heating or stock (animals).

[Richard Watson]

Or you have a earth mass wall system like i have,stays cooler in summer and never freezes in winter even at -9 outside,look at my photos Sean