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Ingenious temperature-sensitive device that automatically opens and closes coldframe lids, greenhouse windows and even skylights.
This works throughout the day and maintains a constant interior climate, something impossible to achieve by manual adjustments.
Requires no batteries or electricity. It starts opening between 55-75°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.