Growing Dome greenhouse automatic vent openers are heat activated and require no electricity to operate. Growing Spaces’ greenhouse designs include upper and lower vents that open and close at an adjustable preset temperature due to the expansion and contraction of beeswax in a piston. Cooling of these geodesic greenhouses is achieved as hot air escapes from the top vents and cold air is drawn in through the lower vents. This creates a “chimney” effect and prevents overheating of our year round greenhouses. The window vents open and close automatically, freeing you to go on vacation without worry about your garden.