How to Heat Pea Gravel for a Greenhouse

Build a raised bed 4 to 6 inches deep and fill with pea gravel. Use dark colored pea gravel for maximum heat retention. Black pea gravel is ideal for a greenhouse floor if available in your region as the gravel will heat naturally and efficiently with exposure to the sun.

Install a heat sink pit by adding a 3 by 3 foot pit of pea gravel in any corner of the greenhouse. Run an open pipe from near the ceiling of the greenhouse to the bottom of the gravel pit. Attach an electric fan at the top of the pipe. The fan recirculates warm air from the top of the greenhouse to the gravel. The air heats the gravel pit during the day and the gravel floor warms the greenhouse at night.

Place electric space heaters in each corner of the greenhouse. Run the heaters for a few hours in the evening to heat the gravel and turn off the heaters at night. The gravel will release heat throughout the night.

Install a wood burning stove in the greenhouse and run the stove in the evening to heat the gravel. Stoke the stove before you go to bed and allow it to burn out during the night. As the stove burns out the gravel will release heat throughout the greenhouse.