THE INFLUENCE OF CEILING HEIGHT IN THERMAL COMFORT OF BUILDINGS: A CASE STUDY IN BELO HORIZONTE, BRAZIL

摘要

Buildings are created to provide adequate climate conditions for the activities performed by occupants. According to thermodynamics and heat transfer principles, the thermal inertia of indoor environments is directly proportional to the volume of that environment. Based on these principles codes of practice for thermal behaviour of buildings have been established in different countries allowing to reduce ceiling heights while influencing indoor air temperature and reducing the indoor environment thermal inertia. For hot weather locations, such as in tropical countries, during most of the year, the reduction of ceiling heights causes a small increase in indoor temperature of environments. In addition, studies both in laboratory and based on mathematical models show that the variation in temperature between the upper and lower layers of an internal environment can reach up to 4 ℃. Another consideration to be observed is that internal environments must have openings for ventilation, a mechanism that helps to control air temperature and the human sensation of heat. Taking as example the Belo Horizonte Building Code, a town in southeast of Brazil, in Minas Gerais State, between 1940 and 2010, when the usual minimum ceiling height reduced 40 cm, there were no compensatory changes in the Building Code of Practice related to the ventilation openings or other heat-control mechanism. In the last decade, other standards and technical manuals on the subject emerged, with certification systems and energy efficiency rating similar to the Green Building, such those existing in several countries. Aiming to evaluate the ceiling height influence on the environments' internal temperature, for this study three full-scale models, of 8 m~2 room area, and window area of the 1/6 floor area, according to the minimum standards established by the Belo Horizonte Building Code of Practice were constructed. They were built in of ceramic blocks structural masonry, varying the ceiling height in the range of 3.00 m, 2.80 m and 2.60 m allowed by technical regulations since 1940 up today. In each one, thermocouples were installed at different heights for monitoring the internal temperature without ventilation, collecting data from winter to summer. Preliminary results indicates that temperature increases of 1℃ for each 20cm reduction As the temperature range of human comfort is small, these variations, however subtle, may cause thermal discomfort to users.