Energy conserving is an important issue in greenhouse farming. Because greenhouse operations consume large amount of fossil fuel energy, energy conservation is necessary for securing famers' income and alleviating global warming. Surplus air thermal energy (SATE) in greenhouses exists even in the cold season, but it has not been utilized for greenhouse operations. In this research, a greenhouse system to capture and use SATE for cooling and heating in greenhouse farming was operated and its performance was evaluated. This system consists of a heat pump system including heat storage tanks, fan-coil-units in the greenhouse and an electric heater for supplemental heating. This system was located in Hwasung, Korea and operated in the cold season. The amount of SATE was measured to be between 258.3 and 6259.0 MJ/month for a glass house with a 100 m(2) floor area. The energy conservations were determined to be maximum of daily 76.3% and monthly 25.7%. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.