The recent energy crisis and the environment impacts of building industry have led to the active promotion of principles of sustainable development in recent times. Minimization of energy usage is the key to improve sustainability where the actual impact is assessed on the basis of life cycle cost estimates. In this context, the performance of insulated roof slabs which can be used as an alternative to conventional light weight roofs, have been assessed in detail especially with respect to air conditioned buildings. It is shown that insulated roof slabs could have a desirable behaviour with respect to life cycle performance in addition to providing other benefits such as cyclone resistance and higher robustness to the building. (C) 2009 Elsevier B.V. All rights reserved.