To keep the Greenhouse at a constant temperature day and night the best way is to use heat banks.
Heat banks come in many forms from the concrete in the floor to commercially available heat trap systems.
Fundamentally heat banks are a storage system that stores
the heat from the sun during the day and releasing the heat at night very much like your Hot water Cylinder in your house. The difference is the hot water Cylinder uses electricity or gas to heat the water, where heat banks in the Greenhouse use daytime heat.
We recommend using 1000 litre Cubes or 200 litre drums painted black as a cheap alternative to a commercial system.
The cubes and the drums are available through out the world New or old and once painted and filled with water will store large quantities of heat for the Greenhouse. Another benefit of cubes and drums they make great supports for the work tables etc
We have been using heat banks for over ten years now and believe the results you will see will truly amaze you.
With this method and the extra insulation that we recommend you will be able to grow all your Favorite fruit and vegetables all year round.