<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css"> <script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <!------ Include the above in your HEAD tag ----------> In small greenhouses, the curtains can be opened and closed with a hand crank to save costs. Enclose an insulating layer of air to reduce the volume that is heated. A variable speed fan motor allows for more precise ventilation volume control and reduces overall power consumption. <a href="https://www.autoventllc.com/greenhouse/vent-motors">Greenhouse side curtain motor</a> can quickly become too hot to produce healthy crops, even in winter. Additional cooling may be required during the summer months beyond the ventilation capacity of the fan.