Environmental performance of buildings is based on social, human, technical and economic aspects to promote sustainability. The technical actions, such as bioclimatic design, adequate flows of energy and water in heating and cooling systems, a specialised selection of construction materials, etc., involve a no conventional way to build, and so, its costs are unknown. An approach focused on the economical influence of these specific criteria would make possible that owners and other public and private sectors put these products into service and place it on the market. This case study provides an analysis and economic evaluation of different altenatives, specifying separately the influence of each criteria. Therefore the study includes a cost evaluation of all processes, passive and active systems of solar energy, items of bioclimatic design, the use of low environmental load construction material s, rain water system, solar heating, natural and passive cooling, plants as fence and microclimate effect, etc. The analysis comprises the real cost obtained from three low environmental impact houses, recently finalised, compared with the standard building in the city of Valladolid, in Spain
