Reducing greenhouse gas emissions by providing non-fossil fuel energy sources is imminently necessary. The area of particular interest in this paper is the agricultural greenhouse industry. In these structures, significant heating demands are present, especially in cold climates, and are typically met by combusting fossil fuels. In an effort towards a sustainable energy supply, the potential of closed greenhouse systems in a cold climate is explored. In these systems, natural ventilation for cooling and dehumidification is replaced with active systems, and the thermal energy removed can be re-used, reducing the overall heating demand. A transient greenhouse model is created using TRNSYS software and validated with natural gas usage data from a reference greenhouse. The annual heating and cooling demands, effect of varying cover materials and potential for heat recovery ventilation are explored for the most concentrated greenhouse areas in Canada. Copyright (C) 2017 John Wiley & Sons, Ltd.