Thermal efficiency of passive building designs can be improved using phase change materials (PCMs). This study was focused on the development and lab-scale thermoregulation performance of wood fiber(WF)/capric acid-stearic acid(CA-SA) eutectic mixture as low-cost and eco-friendly composite PCM for thermal energy storage (TES). The composite including 52 wt% PCM showed leak-proof property. The structural/morphological characteristics, TES properties, cycling TES reliability and chemical stability of the leak-proof CPCM were investigated by SEM, FT-IR, XRD, DSC, and TGA techniques. The lab-scale thermoregulation performance of CPCM board was also evaluated experimentally. The SEM results indicated that the eutectic PCM was successfully impregnated with WF as the spectral findings confirmed the good compatibility among its constituents. DSC results demonstrated that the CPCM had a melting temperature of 23.38 degrees C and latent heat of 92.1 J/g. TGA measurements revealed that the servicing temperature of the CPCM was much over than its thermal decomposition limit. It had stable TES properties and chemical structure after 600 melting-freezing cycles. Furthermore, lab-scale performance test exhibited that the temperature difference at the inside center of CPCM cubic cell and WF cubic cell was ascertained as averagely 2.67 degrees C during a 72 min-heating period and 1.18 degrees C during a 100 mincooling period. (C) 2020 Elsevier Ltd. All rights reserved.