Ingenious temperature-sensitive devices automatically open and close cold frame lids, greenhouse windows and even skylights throughout the day and maintain a constant interior climate, something impossible to achieve by manual adjustments. Requires no batteries or electricity, it starts opening between 55 to 75°F, depending on how you have adjusted the vent. Strongly recommended for all our glazed season extenders because it dramatically improves plant growth. Screw directly into polycarbonate panels, wood, or metal frames. Use the Standard Vent Opener to lift up to 15 lbs, and the much stronger Gigavent, with black and silver all metal construction, to lift up to 65 lbs.