Energy Efficiency of a High-Rise Office Building in the Mediterranean Climate with the Use of Different Envelope Scenarios

Abstract

This paper investigates different strategies towards advancing the energy efficiency of a high-rise office building by focusing on the building envelope. More specifically, the focus is on the thermal properties of the building envelope and the effect of altitude on energy performance. The studies are focused on Tel Aviv, Israel, a city with a vibrant high-rise building activity. Studying this typology in this Mediterranean climate will be of relevance for other cities with similar climate (e.g. in Middle East, S. Europe, N. Africa) that undergo similar processes of high-rise development. The study is based on thermal simulations of an office reference model at different heights: 8 m (ground level), 82 m, 168 m, 254 m, and 340 m. Alternative facade scenarios were implemented for gradually upgrading the building envelope and studying its relationship with the changing microclimate with altitude (wind speed increase and dry bulb temperature drop) between ground and top level. The envelope scenarios range from clear single glazing, to LowE double-glazing, triple glazing, the addition of external shading devices, and a double skin facade (DSF). The popularity of DSFs has grown over the last decades, due to their potential of improving a building’s energy performance, when compared to a single-glazing curtain wall. The high levels of solar radiation common in latitudes and climates like the one in discussion, result in high cooling loads, especially in relation to the design of glass facades. As a result, studies on the energy performance of DSFs in comparison to a single-glazing envelope become very important for improving energy efficiency. Moreover, published research on DSFs is currently mainly on cold and moderate climates. Energy consumption between ground-to-top floors alters with the changing microclimate in relation to height: heating increases, while cooling drops. Moreover, for an office building in Tel Aviv the energy loads for cooling are much higher compared with those for heating. Results show that single clear glazing performs the worst, while using LowE double glazing in scenario B reduces energy consumption for cooling by 25% from scenario A. The addition of external shading devices in scenario C reduces cooling loads by a further 50% from scenario B. In scenario D triple LowE glazing performs by 1% worse in cooling loads from the double-glazing option, however, comparing scenario E of triple glazing with external shading with scenario C of double glazing with external shading, scenario E has 20% higher cooling loads. The comparison between scenario F of the DSFs with scenario C shows that scenario C performs 8% better in cooling loads. However, the shading devices shade a large portion of the facades, while in the DSF option transparency and visibility are maintained, as well as improving the energy performance of the building. The results prompt for further studies on the energy efficiency of DSF in warm climates.