Supermarkets are energy intensive buildings and present a unique space conditioning challenge because of the interaction between the HVAC system and the refrigerated display cabinets. HVAC system is the largest consumer of energy after refrigeration depending on system design, geographical location and controls. Night ventilation is used extensively as a low energy strategy to cool buildings in climates where night temperatures are suitable. This paper presents a study of cooling benefits of night ventilation for supermarkets with high cooling demand. Energy and environmental data from two stores with high percentage of frozen and chilled goods and with different HVAC systems are presented. Validated models in EnergyPlus are developed for the two stores and their systems. A parametric study of the coupled operation of night ventilation and active cooling for the climatic conditions of south east England is carried out and optimisation strategies are modelled. Results indicate that effective night ventilation can reduce the duration of active cooling during trading times and achieve 17% reduction in cooling annual energy use, 3.3% in total annual energy use while refrigeration energy use is not affected. (C) 2018 The Authors. Published by Elsevier B.V.