A new Energy code for office buildings in Israel, currently under development, is presented. This code is based on a prescriptive approach, which can be easily applied as a tool for the design of office buildings through all the design stages including the early ones. The prescriptive approach suggested is based on the results obtained from an energetic-economic optimization model that provides a recommended and preferred prescription for office building under given constraints. A sensitivity analysis of the optimized solution follows. The sensitivity analysis permits modifications of the recommended prescription allowing for the creation of a wide range of design alternatives and in addition to figure out what are the design variables with the highest impact on the building energy consumption and cost. The way of using the prescriptions as a building code is explained as well as the method to determine the energetic rank of the chosen solution. (c) 2007 Elsevier Ltd. All rights reserved.