Which one is more effective to add to building envelope: Phase change material, thermal insulation, or their combination to meet zero-carbon-ready buildings?

Abstract

Renovation of old buildings is a key pillar of decarbonization approved in the Net Zero Emissions (NZE) scenario. Based on NZE requirements, the share of zero-carbon-ready buildings should reach more than 85%. Adding phase change material (PCM) or thermal insulation is an effective technique to tackle high energy demand in buildings. Relying on CFD-based techniques, PCM phase transition was formulated to compare the thermal behavior of the building including insulation, PCM, or PCM + insulation. Taking into account warm weather along with significant solar radiation intensity, PCM 22 (melting temperature of 20–22 °C), PCM 23 (21–23 °C), and PCM 24 (22–24 °C) were utilized. The results showed that in summer the thermal behavior of the walls containing PCM were better. While in winter, insulation was superior to PCM. Considering the annual energy consumption, it is better to use insulation than PCM. However, it was found that if a combination of PCM plus insulation is used, total energy demand may be lower than in case of single PCM or insulation. For the Middle East region, where electricity consumption is very high in the hot months, using the combination of insulation + PCM 24 has amazing results. The results showed that if PCM 24 + insulation is utilized, the cooling load will be reduced to zero. Focusing on reducing the annual energy consumption, taking advantage of PCM + insulation is beneficial when the share of PCM volume in combination with insulation is less than 44%. Under the best conditions, annual energy demand declined by 12.6% if PCM 22 + insulation is used.