Shape-stabilised phase change materials for reinforced concrete roof cooling: Thermophysical performance study

Solar heat gain through the roof is the primary factor in tropical reinforced concrete (RCC) structures, resulting in high cooling loads that account for a significant portion of the building's overall energy consumption. Advanced retrofit solutions are essential for tackling this scenario by minimising heat conduction and decreasing the reliance on cooling systems. The use of phase-change materials (PCMs) to regulate heat transfer in building envelopes is well-established; however, their application for retrofitting existing reinforced cement concrete (RCC) roofs, particularly in a warm-humid climate, has not been widely investigated. Addressing this gap, the present study introduces a climate-specific, flexible shape-stabilised PCM (SSPCM) developed by incorporating lauric acid (LA) into a natural rubber (NR) matrix to enhance the energy efficiency of RCC roofs. LA–NR composites were synthesised by incorporating LA at concentrations ranging from 10 to 50 parts per hundred rubber (phr). LA–NR composite materials were subsequently analysed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and mechanical tests. The 30 phr LA–NR composite achieved an optimal balance of latent heat storage (34 J/g, melting range: 28– 44 °C), thermal stability, and mechanical integrity, with negligible leakage. Heat transfer tests showed a pronounced thermal buffering effect, delaying the surface temperature rise compared to NR. In controlled RCC slab experiments, SSPCM integration reduced the peak bottom-surface temperature from 50 °C to 39 °C and lowered the lower compartment air temperature by up to 5 °C. These results demonstrate the potential of LA–NR SSPCM as an energy-efficient retrofit layer for enhancing thermal comfort and reducing cooling loads in buildings with RCC roof. • A novel Shape-stabilised PCM using Lauric acid (LA) and Natural rubber (NR) for RCC roof retrofitting in warm-humid climate. • 30 phr SSPCM offers optimal thermal & mechanical performance with minimal PCM leakage. • Increase in latent heat of NR up to 34 J/g with incorporation of LA. • 22% reduction in RCC slab temperature with SSPCM . • Drop in indoor air temperature by ∼5 °C with SSPCM .