Energy efficient retrofitting of buildings in Brazil

Abstract

Natural ventilation in buildings is a beneficial passive strategy for conditioning buildings for different climates. Beside its potential to promote energy efficiency it can improve indoor air quality in buildings along with health and wellbeing for their occupants. The achievement of these benefits is related to a good architectural design where type, geometry and location of openings are defined. Different types of openings provide different air change rates. A parameter to distinguish windows regarding their ventilation efficiency is the discharge coefficient. It describes the actual airflow in relation to the ideal airflow. The discharge coefficient varies according to the type of opening, ventilation area besides other physics factors as pressure, velocity and air density. Recent researches on the topic have used the same value of discharge coefficient for different window types. This simplification implies inaccurate results in the estimation of airflow provided by the openings. More reliable values based on experimental analysis can be found in the literature for some types of openings. In order to complement these studies this research aims to characterize additional window types produced in Brazil and Germany. Wind tunnel measurements are performed at the State University of Campinas (Unicamp). With measured discharge coefficients thermal building simulations are done for a typical office room in Brazil. It is found that the use of double glazing halves the energy demand for cooling. A simple control algorithm for air conditioning is developed. In comparison with a usually used constant setpoint for air conditioning units the energy demand for cooling can be reduced up to 93%. Additional tracer gas measurements for direct measurement of the air change rate are done in an office room at the HafenCity University (HCU) are done. A strong dependency between wind flow direction and air exchange rate is proved.