The design of self-built houses in the city of Campinas, Southwest of Brazil, is discussed in relation to the value given to comfort elements. Considering that a large percentage of the Brazilian housing production is self-built, the impact of this construction activity is considerable. It affects the comfort of the occupants of such houses and on a larger scale the micro-climate. Due to specific local Brazilian economic and social structures, as well as urban growth patterns, self-built houses, houses built by owner families, make up a substantial percentage of Brazilian housing production, around 60%. Due mainly to low-quality design solutions, self-built houses present on the whole a low environmental comfort standard. Ventilation as design strategy for thermal comfort is very important in the city with hot-humid climate in summer. Cross-ventilation refers to conditions where a given space is connected by apertures to both pressure and suction areas of the exterior. Sometimes the expression is loosely used whenever the space has more than one access to the outside. This may be misleading, for when all the openings of a space are facing zones at similar air pressures there will be very little internal air flow. Air flow in a building is determined by three basic factors, size and location of openings, their orientation in relation to prevailing wind and the presence of barriers and other constructive elements near the openings and windows. A survey carried out in five self-built settlements in Campinas shows that only 25% of the houses are suitable for natural ventilation. By applying Givoni's results considering inlet and outlet openings, it is shown that only 40% in average of air flow is related to the analysed ambient. Besides that, lot perimeters are walled, creating wind barriers. Most houses respect the street front setback of 4 meters stipulated by local building codes. Side setbacks are however, even if present in the first stage of building, often incorporated into the house for increased indoor space. From all houses analysed, it can be seen that scarcely 1 % could obtain the desired air velocity and direction to provide thermal comfort for their inhabitants. Site planning with regard to wind direction is therefore a real necessity for the self-builders in the city.1 269274Labaki, L.C., Kowaltowski, D.C.C.K., Bioclimatic and vernacular design in urban settlements of Brazil (1998) Building and Environment, 33 (1), pp. 63-77. , PII S0360132397000243Kowaltowski, D.C.C.K., Labaki, L.C., Pina, S.A.M., Bertoli, S.R., Ruschel, R.C., Favero, E., Francisco, L., Gomes, V.S., (2003) Analise de Parâmetros de Implantação de Conjuntos Habitacionais de Interesse Social: Ênfase Nos Aspectos de Sustentabilidade Ambiental e da Qualidade de Vida, , relatório parcial de projeto de pesquisa FINEPDesempenho Térmico de Edificações - Parte 3: Zoneamento Bioclimático Brasileiro e Diretrizes Construtivas Para Habitações Unifamiliares de Interesse Social, , NBR15220-3, 04/2005Givoni, B., (1998) Passive and Low Energy Cooling of Buildings, , Van Nostrand Reinhold, new York, NYBoutet, T.S., (1987) Controlling Air Movement: A Manual for Architects and Builders, , Mac-Graw Hill, New YorkBittencourt, L., (2004) Introdução A Ventilação Natural Nas Edificações, , UFAL