Thermal transmittance evaluation of concrete hollow blocks

Abstract

Buildings are worldwide responsible for a paramount consumption of energy. Inside them, electrical power is used for a wide range of applications. One of them is directly related to the equipment required to provide thermal comfort to occupants, which may be responsible for a substantial amount of the whole-building energy consumption. The amount of power required by HVAC (Heating, Ventilation and Air Conditioning) systems depends on several factors and, one of the most important, is the conduction load through the building envelope. In this context, a large range of construction elements has been used worldwide. In emerging countries such as Brazil, concrete hollow blocks have become more usual over the past few years. This can be explained by the advantages such as their higher strength, their large cavities – which can be useful for pipes installation –, the faster execution and the small amount of waste produced during the construction process. For the assessment of building energy efficiency, the thermal transmittance evaluation of hollow blocks is required. In this way, this study aims at obtaining values of thermal transmittance for different cavity configurations of concrete blocks, by performing CFD simulations. The transmittance values obtained are compared to those calculated using the methodology presented in international standards. In the results section, it is shown that large cavities provide higher transmittance values and that radiation effect may play an important role on the overall heat transfer through concrete hollow blocks.