Enhancing thermal performance of cross-laminated timber using phase change materials and biochar composites

Cross-laminated timber (CLT) is an excellent structural material. However, when used in building envelopes, its low thermal storage performance makes indoor environments sensitive to external temperature changes. In this study, phase change materials (PCMs) are utilized to enhance the thermal performance of CLT, and biochar is employed as a supporting material to address PCM leakage issues. To apply the mixture of PCM and biochar to CLT, this research utilized gypsum board, which is mainly used for fire resistance in CLT, and additionally manufactured and evaluated a binder mixed with cement considering the structural part of CLT. TGA analysis of PCM/biochar composites shows weight loss rates of 41.05 %-48.60 %, indicating significant PCM impregnation and thermal stability below 120 degrees C. When PCM/biochar boards are integrated into CLT as exterior and interior layers, a gypsum board exhibits slow heat transfer with a reduction of 1.5 degrees C in the maximum surface temperature compared with a cement board. In addition, the gypsum board requires 350 min to reach the peak temperature. In contrast, the cement board reaches a maximum temperature of 14.8 degrees C in 300 min, thus showing a faster thermal response. The improved thermal performance of the PCM-integrated materials enhances the heat storage performance of CLT by approximately 40 % compared with conventional CLT. This study demonstrates the potential of hybrid CLT with PCM/biochar composites for advancing sustainable building practices.