DIY ProjectsGreenhouse & Indoor Gardening

How to Heat a Greenhouse Without Electricity

There are two main concepts concerning heating a greenhouse without electricity. The first is by collecting the sun’s warmth as sunlight hits upon a dense material called thermal mass, such as rock and water. Thermal mass will absorb a lot of heat throughout the day and release that heat when temperatures drop at night. Utilizing thermal mass in a greenhouse is easy since it already receives much sunlight.

The second concept is with composting, since compost piles produce heat as the microorganisms within them break down the organic materials into compost.

Materials You Will Need
  • Small stones or gravel
  • White paint
  • Black paint
  • Paint brushes
  • Cinder blocks
  • Water container(s)
  • Ceramic pots
  • Wire mesh
  • Organic materials (leaves, twigs, etc.)
Step 1

Put down a layer of small stones or gravel in your greenhouse. This creates a layer of thermal mass that will remain dry and clean.

 Step 2

Paint all the surfaces in your greenhouse that you want to reflect light, with white paint.

Step 3

Arrange your cinder blocks in the way you want them as support for water containers or to make benches or table supports. The cinder blocks will absorb heat from any sunlight that touches them.

Step 4

Paint the cinder blocks black. This will increase the efficiency in absorbing heat.

Step 5

Put one or more water containers in your greenhouse where you want them to absorb and release heat, and fill them up with water. It isn’t critical but these water containers can also be painted black.

Step 6

Create a more aesthetically pleasing greenhouse by adding ceramic pots. They will absorb and release heat in the same way as cinder blocks and will look much nicer.

Step 7

Put a ring of wire mesh where you want your compost pile. Be very careful with this. Compost piles, especially large ones, are known to create immense amounts of heat. Compost piles can spontaneously combust into flames, so just be aware of what you are doing if you have a large compost pile in your greenhouse especially if it is attached to your house!

Step 8

Add compostable material to your compost bin, such as any plant clippings, fallen leaves and weeds and keep it moist.

 Step 9

Enjoy an increase in your greenhouse temperature without raising your electricity bill!

Mike McGroarty is a Garden & Greenhouse contributing editor, the owner of McGroarty Enterprises and the author of several books. You can visit his website at and read his blog at

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