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 55-95°F, depending on how you have adjusted the vent. Strongly recommended for all our polykeder season extenders, because it dramatically improves plant growth. Screw directly into wood. Use the Standard Vent Opener to lift up to 15 lbs.
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