Ventilation in Self-Built Houses - A Study Through Wind Tunnel Measurements in Campinas, Brazil

摘要

Natural ventilation of buildings is a design strategy for the passive cooling of buildings that can be considerably efficient if properly undertaken. In Brazil, as in many other developing countries, spontaneous (self build) housing is often of poor quality. Also, each of these dwellings has a negative impact on the neighbouring ones and on the impact on the urban environment. In the city of Campinas, Brazil, with its hot-humid climate, adequate ventilation is essential for thermal comfort. Self-built houses are usually small initially but are often subject to frequent additions that are undertaken without any attention to adequate ventilation. The present work analyses the influence of these non-planned changes on the internal air movement by means of wind tunnel measurements. Two houses situated in an urban settlement in the city of Campinas were studied. In each case the analysis started with the initial situation and then proceeded to determine the influence of modifications. Thus four physical models were constructed and tested. An atmospheric boundary layer wind tunnel was used in which measurements of wind speed were made at one point outside and at five points inside the models, for different angles of the incident wind. Results show that additions to a back-of-the-lot house significantly impair air movement indoors, due to blocking recirculation. In the second house, where a roof was added in the front setback, an improvement was observed only in the internal point nearest to the facade, but internal circulation was actually reduced. In conclusion, it was observed that narrow lots and the lack of design orientation to self-builders lead to houses with no adequate setback, so that the positioning of openings does not promote good ventilation as required for both thermal comfort and indoor air quality.