Impact of natural night ventilation in energy performance of office buildings with windows filled with Phase Change Materials (PCMs) in a semiarid climate

Abstract

Phase Change Materials (PCMs) are materials with high latent heat that solidifying at a certain temperature. When PCMs are incorporated into the glazing façade of buildings are able to reduce cooling loads, control daylight transmission and overheating. Currently, office buildings have fully-glazed façade without opaque elements, so they have a lack of thermal inertia. PCM glazing arises as a solution to improve the thermal performance of the façade. To guarantee the maximum potential of PCM glazing, the phase change must occur during whole work hours. Semiarid climates (Bsk according to Köppen Geiger climate classification) are characterized by high temperature and solar radiation during more than half of months of the year and high fluctuation temperature between day and night. This type of climate has the potential to use night ventilation to ensure the phase change from liquid to solid of PCMs in office buildings. Then, this paper aims to analyze the impact of different night ventilation ratios in the energy performance of an office building with PCM glazing located in Santiago of Chile by means of an energy simulation tool. A Prototype Building Model of a medium-sized office building for Albuquerque of 4980 m2 and a window-to-wall ratio of 0.3 is considered as a case study. To proof the potential of night ventilation, three values of infiltration rate are evaluated, 1 ACH, 3 ACH and 5 ACH; and two different paraffin of Rubitherm® company RT25HC and RT28HC filled the window. Energy simulations are carried out using EnergyPlus and a heat transfer model of PCM glazing previously developed and integrated to EnergyPlus. The results show the benefit of natural night ventilation during the summer season to ensure the complete phase change and decrease the cooling energy consumption for window filled with both PCMs considered.