Conventional greenhouses are run with a combination of solar, electricity and/or fuel to heat the interior of the structure. Many greenhouse owners are looking for alternative ways to heat a greenhouse. There are many methods of alternative heating for greenhouses, using both natural and man-made material.
Heat sinks are any material that can soak up heat during the day and slowly release it at night by sinking the heat into the material. Examples of heat sink materials include tile over concrete and dark brick used in floors or walls. Paint soda bottles, plastic containers or paint cans black, and build stacked walls out of them; the material will gather heat during the day, using the black paint as an attraction to the heat.
Paint 55-gallon barrels black. Line the barrels up around the interior of the greenhouse or use them as part of the walls. Fill the barrels with water. The water in the barrel will heat up as the sun heats up the barrels during the day. The water will hold the heat as long as the barrel surfaces remain hot. During the night, when temperatures cool down, the water will release the heat into the greenhouse.
Run metal pipes through the floor of the greenhouse. Allow hot water to flow through the pipes. The metal of the pipes will help retain the heat of the water and send that heat into the greenhouse through the floor. Using a conductor such as concrete or stone makes this method more efficient.
Dirt is a natural insulator. Dig out a pit using either of two options: dig a pit deep enough to make all four walls of the greenhouse out of dirt, or dig out three walls on the side of a hill then close in the fourth side with heat-gathering material. According to the School of Forest Resources and Environmental Science at Michigan Tech, using this method keeps the greenhouse 10 degrees warmer than other greenhouse methods on a consistent basis.
Make the greenhouse walls out of stacked tires and compacted dirt. Stack the tires using the same method brick layers use to build walls with overlapping rows. Set up the first row of tires and pack dirt tight inside and around them. Set the next row up with each tire resting on two tires below it and pack with dirt. Keep building rows until the walls are complete; then put the glass or solar panels on top for the roof. The tires will attract the heat; the dirt will hold the heat until the sun sets. The heat is then released during colder temperatures at night. This method will also maintain a near constant temperature in the greenhouse.
Stone and gravel are another natural heat sink and insulator. Using stone as walls will help regulate the temperature of the greenhouse to a consistent warmer temperature. Using gravel, slate or patio stone for the flooring helps retain heat inside the greenhouse, and the stone releases the heat after the sun sets. Make sure to pack the gravel or stone tight to keep the heat in the floor during the day.