Energy is wasted in domestic buildings when rooms that are heated are not occupied. Allowing those rooms to cool reduces the inside - outside temperature difference and therefore rate of heat loss, resulting in an energy saving. This suggests a cost effective way to upgrade an existing modern heating system, especially in older properties where other energy saving possibilities are limited. Assessing the savings achievable requires an analysis of a range of influencing factors, such as house type and age, location and occupancy patterns. Door opening has a major influence due to the impact on air exchange between heated and unheated zones in a house, so this was also considered. Annual simulations were carried out on dynathic models of the thermal and air flow interactions, for all combinations of influencing factors, to compare the potential energy savings of zoned versus non-zoned control. Savings of between 12% and 31% were obtained in the case of a semi-detached house model, and between 8% and 37% for a single storey bungalow. The largest percentage savings occurred in older properties, with interconnecting doors kept closed, and for the more intermittent types of occupancy. The average saving obtained for both house types was around 20%. (C) 2016 Elsevier B.V. All rights reserved.