Automatic Roof Vent Opener for Palram-Canopia® GreenhousesDESCRIPTION The Automatic Vent Opener was designed to automatically control the temperature in all Palram Canopia Greenhouses. As the air inside the greenhouse warms, the vent gradually opens to allow the correct amount of air to flow into the greenhouse and closes when the optimal temperature is reached. The vent arm was designed with the use of natural wax that expands to push a piston, which raises the window, as the air gets warmer then contracts