Thermal mass and the effects on heating and cooling demands – an experimental study of an exposed concrete floor

Abstract

The increase of thermal mass in buildings is discussed as a useful measure for reducing the energy demand for heating and cooling while contributing to improve the internal comfort. Several studies confirmed its positive effect, but few conducted a solid comparative measurement campaign and rarely in comparative conditions. The present work reports the results of an extensive comparative campaign in a test cell facility, where the internal conditions are measured in two identical rooms. One of the rooms was equipped with a large concrete mass while the other was constructed with a thin wooden floor. Measurements were conducted for circa a month, divided in four phases. The internal temperature of the two rooms was kept within typical boundaries of actual office rooms by a water-based cooling and heating systems. The energy demand of both heating and cooling was measured. Occupancy was simulated by a mannequin and by the lighting, both active only in office hours. The results demonstrated a positive impact of the thermal mass on the energy use. Since the test rooms are highly insulated, the energy use associated to cooling was dominant. During the experimental campaign, a reduction of up to 44% of the energy demand due to cooling was registered.