Exaco Trading  G7105 Automatic Roof Window Opener for the Bio-Star Pioneer Greenhouses (Discontinued by Manufacturer)
The Bio-Star Greenhouse is the second generation entry level greenhouse from Exaco Trading. This automatic window opener attaches to the roof window and opens when temperature gets to about 72 degrees. It does not require electricity but contains a special paraffin oil that expands in heat and pushes the window open.  When the temperature goes down, the oil contracts and the window closes. An excellent accessory that helps monitor greenhouse temperature when you are not home and prevents plants from becoming overheated.