Experimental and simulation study of lightweight roof with thermal energy storage for energy-efficient building envelope

The development of energy-efficient, lightweight building envelopes will play a vital role in reducing the increasing demand for energy to improve the indoor thermal performance of buildings. This study compares the indoor thermal performance of a lightweight, energy-efficient building element called a Hollow Polycarbonate Sheet (HPCS). Lightweight material panels containing Polyurethane Foam (PUF), HPCS, Phase Change Material, Thermal Paint, and Bentonite Clay were developed. Their positions were adjusted to optimize heat reduction through them. These panels were used as roofs in six different test houses (TH), namely Reference Test House (R-TH), Bentonite Clay Test House (B-TH), Thermal Paint Test House (TP-TH), PCM Test House (P-TH), Thermal Paint-PCM Test House (TPP-TH), and Thermal Paint-Bentonite Clay Test House (TPB-TH), all of similar dimensions. Experimental results indicate that TPP-TH shows a 9.86 % reduction in indoor surface peak temperature compared to R-TH. Furthermore, TPP-TH exhibits a maximum temperature reduction (MTR) of 15.3 °C, an average temperature fluctuation reduction (ATFR) of 6.5 °C, and a reduction in decrement factor (DF) of 46.52 % compared to R-TH. Similarly, in the indoor thermal comfort analysis, TPP-TH demonstrated the best thermal performance among all the THs. These observations suggest that combining PCM with thermal paint enhances the indoor thermal performance of the lightweight building element compared to other THs. Using only PCM in lightweight building materials negatively impacts discomfort hours. Additionally, a Finite Volume-based Open FOAM ® CFD solver was used to simulate the TPP-TH Test house, and it was observed that the simulation result is in close agreement with the experimental data.