© 2014 The Authors. Published by Elsevier Ltd. During the last decade, housing construction in Mexico has increased dramatically, despite the economic and financial crises, it is one of the main drivers of the Mexican economy; the government has supported programs to develop social housing in order to assist low-income families. This type of initiatives has allowed low-income people to own a place to live, but it has also promoted the spread of housing developments with house models of similar characteristics in the very diverse geographical and climatic zones of Mexico. Even though some of the dwellings have few differences depending on the region they belong to, they do not reflect climatic adaptations. The correct selection of the envelope materials is one of the first and most effective passive strategy that must be considered in the design of a housing. However, just selecting the materials by knowing their thermal properties is not enough to make an appropriate decision about the construction system. For this reason, we need a tool like Ener-Habitat, which allows a quick assessment of thermal and energy performance of a building system consisting of several layers, through the time-dependent calculation of heat transfer, suitable for high thermal mass materials, such as those generally used in Mexico and the climates of Mexico with high solar radiation and large temperature swing during the day. The study propose a method to analyze the cost and energy benefit of building systems, and as example analyzes some walls building systems, in a hot-dry climate city of Mexico, during the air conditioning season. This tool allows, at early stages of architectural design, quick assessments for decision taking on the building systems choice, in relation with better energy performance. Ener-Habitat was created by researchers from six academic institutions in Mexico and was funded by the National Council for Science and Technology and the Ministry of Energy of Mexico.