Although every greenhouse is a solar greenhouse to some extent, there are differences in the type of solar heating and lighting that you can use. The covering you use, whether it is fibreglass, glass or heavy plastic, traps the heat from the sun inside each day. The trick in having a successful greenhouse is learning how to store this solar heat to keep the temperature the same during the night. A traditional greenhouse captures the solar heat during the day, but it loses significant amounts of this heat at night.

One way of maintaining the heat during the night is to use what is called passive solar heating. This consists of collecting water in barrels. The water retains the heat and allows it to escape during the night and heat the greenhouse. Another way, which involves more expense, is to have a concrete wall or rocks that can supply the needed heat.

You can also revert to using electricity to power a heater during the night. If you use a heat pump, it will pump the stored heat from the water into the greenhouse, thus maintaining the humidity that the plants need. Without having humidity of some kind in addition to the heat, the plants may become dehydrated.

If you have your greenhouse attached to a building, you can consider having that wall covered with bricks. Those that use this system paint the bricks black so that they absorb the maximum heat from the sun during the day. Although this method does work well, it takes a lot of extra time getting the greenhouse set up.

Recent research has looked at using cheap chemical compounds called eutectics to maintain the solar heat in a greenhouse. These are salts that store the heat from the sun at a constant temperature for use during the nights and for cloudy days.

You do need to have a backup system for heating in greenhouse because you can't rely on receiving heat from the sun on a continuous basis.