Building energy use accounts for almost 50% of the total CO2 emissions in the UK. Most of the research has focused on reducing the operational impact of buildings, however in recent years many studies have indicated the significance of embodied energy in different building types. This paper primarily focuses on illustrating the relative importance of operational and embodied energy in a flexible use light distribution warehouse. The building is chosen for the study as it is relatively easy to model and represents many distribution centres and industrial warehouses in Europe. A carbon footprinting study was carried out by conducting an inventory of the major installed materials with potentially significant carbon impact and material substitutions covering the building structure. Ecotect computer simulation program was used to determine the energy consumption for the 25 years design life of the building. This paper evaluates alternative design strategies for the envelope of the building and their effects on the whole life emissions by investigating both embodied and operational implications of changing the envelope characteristics. The results provide an insight to quantify the total amount of CO2 emissions saved through design optimisation by modeling embodied and operational energy. (C) 2010 Elsevier Ltd. All rights reserved.