Updated: June 6, 2019
Though greenhouses are effective for growing vegetables in different climates, heating them during long winter nights can prove quite costly. To reduce heating costs, it’s worth considering a self-heating greenhouse. A self-heating greenhouse does exactly what it says, helping your plants thrive throughout the darker months and helping you by saving energy.
The best way to regulate temperature within your greenhouse is to build a heat sink. To create a heat sink you’ll need to create an insulated pit in the bottom of the greenhouse; people commonly use rubble to fill the pits, however bricks and gravel together work better by reducing the volume of air pockets within the pit. The heat sink is a heat trap storing vast amounts of thermal energy from the hot air in the greenhouse that would otherwise escape during the evening. To aid the heat sink you may wish to draw hot air into the heat sink. Solar power fans that operate during the daytime are an easy way to accomplish this. As the greenhouse begins to cool down, the heat that has been stored within the bricks and gravel or rubble is radiated, heating the greenhouse once more.
Building your own heat sink is a simple process and is extremely cost effective. The only materials you’ll need are the insulation and the object that’s going to conduct the heat (for this you can use bricks, rubble or other dense materials) and some piping.
How to build a heat sink
Dig the area for the heat sink. The hole that you create will depend upon the size of your greenhouse. An average greenhouse (10’ x 10’) will only need a heat sink of approximately 3’ x 3’.
Dig the heat sink towards the centre of your greenhouse as this will ensure that the heat is distributed evenly throughout your greenhouse. The heat sink should also be centralized because if it comes into contact with glass or outside of the greenhouse it’ll lose heat quickly, making it less efficient.
Fill the hole with dense materials such as slabs, bricks, concrete and other materials. Due to the density of these materials they conduct and store heat quite well.
Add the hollow pipe to the centre of your heat sink. The pipe shouldn’t be too thin as this can prevent the natural diffusion of the warm air. The pipe should also be wide enough that it will release an adequate amount of warm air to heat your greenhouse.
- Build your greenhouse facing the sun.
- Paint a wall that’s opposite or adjacent to your greenhouse in white paint to reflect sunlight and heat the greenhouse.
- Consider building beneath the earth, as with a walipini greenhouse, since the temperature below the earth doesn’t vary by more than a few degrees throughout the year.
Video example from the BBC Show It’s Not Easy Been Green: