Solar energy is considered one of the most prospective sources of renewable energy for greenhouse heating in cold period for Mediterranean climate. In this paper, the thermal performance of a north wall made with phase change material (PCM) as a storage medium in east-west oriented greenhouse is analyzed and discussed. CaCl2 center dot 6H(2)O was used as a PCM. A numerical thermal model taken into account the different components of the greenhouse (cover, plants, inside air and north wall PCM) and based on the greenhouse heat and mass balance, has been developed to investigate the impact of the PCM on greenhouse temperature and humidity. Calculations were done for typical decade climate of January in Marrakesh (31.62 degrees N, 8.03 degrees W). Results shows that with an equivalent to 32.4 kg of PCM per square meter of the greenhouse ground surface area, temperature of plants and inside air were found to be 6-12 C more at night time in winter period with less fluctuations. Relative humidity was found to be on average 10-15% lower at night time. (C) 2011 Elsevier B.V. All rights reserved.