Evaluation of building glass performance metrics for the tropical climate

Abstract

Increasingly compact high density urban development in cities has allowed urban heat island effect to take root and increase the energy consumption of commercial buildings to cool its interior. Although the extensive use of glass façade has allowed these buildings to harness daylight to light up the building interior, it has also allowed substantial solar energy to enter and heat up the building. This is especially critical in hot and humid tropical regions, where reducing solar heat gain, while minimizing heat loss are equally important.The evaluation of glass performance is often conducted using active measurement, which make use of known radiant source. However, this type of setup cannot be applied for testing under non-controlled weather. Though a passive test procedure can be conducted under actual weather conditions using the outdoor test chamber, it is not suitable for a large-scale testing and fast on-site characterization. In addition, this test is limited to the fabricated glazing and thus could not predict potential issues in the design stage. Advances in simulation techniques have enabled building professionals to evaluate the glass façade of a building at the design phase. However, the typical simulation tools are unable to integrate the high performance glazing description, which is generated thanks to advances in coating technology, using the existing glass models. Furthermore, these tools are often lack of local weather models that plays an important role in accurately assess the solar heat gain admitted into the building.This paper provides useful information on different high performance glass façades and assesses their applicability for green building in a tropical country like Singapore. The research effort encompasses an improvement in the methodology used to predict solar irradiance through building glass that incorporates seamlessly the advanced glass models into the solar irradiance simulation. In addition, this will show how to effectively estimate the actual sky behavior via a measured data-based optimization process. A comparison of the simulation results with the measurements from an outdoor climatic test chamber under tropical climate will be performed. An assessment based on the typical glass performance metrics (e.g. U-value and Solar-Factor) together with measured energy savings obtained with the use of different high performance glass façade compared to clear float glass as a control will also be presented.