Thermal performance of naturally ventilated office buildings with double skin façade under Brazilian climate conditions

Abstract

Double skin façades (DSFs) are gaining recognition as a technology that, while giving a modern transparent appearance to buildings, have the capability to moderate the indoor thermal conditions and the potential to reduce energy demands.. A typical DSF consists of an additional fully glazed external skin installed over the conventional building façade forming an air cavity in which sunshade devices are often installed to prevent overheating in the internal rooms. The majority of the existing studies on DSF are based on air-conditioned models under temperate climate conditions, where most DSFs are implemented. However, developments in warmer climate countries such as Brazil are also considering the application of this technology as a solution to improve thermal performance in buildings. Therefore, investigations to understand the DSF thermal and airflow processes and implication of its use in naturally ventilated buildings under such climates are needed. The aim of this study is to determine the thermal performance of office buildings with DSF under Brazilian climate conditions. Firstly, the key parameters affecting the thermal performance of buildings with DSF are identified through critical literature reviews. Using an office building as a reference model, computational thermal dynamic simulations are performed to demonstrate the influence of each individual key parameter on the building‘s thermal behaviour. From the findings of the parametric analysis, optimized models that utilise a combination of solutions to maximize the building thermal performance are developed and analysed. Finally, acceptable thermal comfort levels of the optimized model in different Brazilian climatic regions and periods of the year are determined. This study evaluated the key parameters affecting the thermal performance of buildings with DSF, including: the significance of material selections in design solutions to maximize airflow through the building; the prevention of unintentional reverse flow on the upper floors and maintenance of balanced airflow rates across all floors; the impact of solar incidence and wind conditions on the DSF‘s thermal performance. Results from the simulations of the optimized model under different bioclimatic zones of Brazil indicated that in most parts of the country the thermal comfort acceptance levels are as low as 60%, especially in the hotter areas of centre west regions, coastal areas and north of the country. The outcomes of this research provide insight and understanding on the functioning of the DSF in naturally ventilated buildings in warm and hot climates. DSFs in naturally ventilated buildings under Brazilian climates generally presented lower thermal acceptability when compared to single skin models due to the high outside temperatures and the airflow resistance caused by the application of the second skin. Their application will therefore not have direct benefit to the thermal performance.

Date of Award	Nov 2015
Original language	English
Awarding Institution	University of Brighton