Currently, 75% of existing homes were built before the creation of the Chilean Thermal Regulation (TR); hence, these are responsible for the increase in energy consumption in the residential sector. The user pays the cost of energy consumption which supposedly keeps their homes in comfortable conditions, affecting the most vulnerable sectors, where people mostly live in 40 m 2 dwellings which were built without considering any energy or environmental aspects. The energy and environmental retrofitting of this existing housing stock would reduce energy consumption for heating, cooling and other aspect, and it would allow achieving the expected comfort. The aim of this study is to develop performance-based strategies for energy and environmental retrofitting of existing social housing in Chile. It proposes to consider performances which normally are not included in refurbishment programs, such as: hygrothermal behavior of the envelope, reduction of heating demand, air permeability and indoor air quality. In this paper it is explained how a representative sample of houses was selected. Also, it details one of three methods (the experimental one) and its results, to understand the real situation of the existing social housing stock.