The effectiveness of phase change materials in relation to summer thermal comfort in air-conditioned office buildings

The incorporation of Phase Change Materials (PCMs) into the opaque envelope of lightweight buildings is a good solution to compensate for the small thermal inertia, which usually entails pronounced overheating and high space cooling load in summer. However, the position and the thickness of the PCMs, as well as their thermal properties, must be attentively selected in order to ensure their effective operation. This paper shows a comprehensive investigation about the effectiveness of a commercial PCM, available in the form of mats, when installed within drywall partition systems in air-conditioned lightweight office buildings. The study is based on dynamic simulations carried out with EnergyPlus on a typical office building, with the aim to calculate the indoor operative temperature and the cooling load under thermostatic control. The performance for the base case (without PCM) is then compared with the case where PCM mats with various thickness and melting temperature are applied. The analysis is repeated in three different locations, ranging from Southern Europe (Rome, Italy), Continental Europe (Wien, Austria) and Northern Europe (London, UK). The results of the simulations highlight that in lightweight air-conditioned office buildings PCMs contribute to attenuate the inside surface temperature peak by around 0.5 °C, while also reducing the peak cooling load by 10% or even 15%, depending on the PCM thickness and on the outdoor climate. The conclusions may help designers to make the correct choices in terms of thickness of the PCMs, scheduled rate of nighttime ventilation and value of the peak melting temperature.