This paper presents an experimental determination of energy requirement for greenhouse heating. The overall heat loss coefficient, heat input, the control factor for air-tightness, the rate of heat loss and the thermal screen effectiveness were calculated. The relationships between the overall heat loss coefficient and the wind speed, and the outside temperature were modelled, including the measured and calculated values. It was found that the thermal screen effectiveness was 16 and 19.8% for the polyethylene (PE) and polyester screens, respectively. Copyright (c) 2005 John Wiley & Sons, Ltd.