Infrared Thermography-Based Assessment of Thermal Bridges and In Situ Thermal Performance in Occupied Precast and Reinforced Concrete Apartment Buildings

In this study, infrared thermography (IRT) was used to quantitatively evaluate the thermal bridge characteristics and in situ thermal performance of exterior wall-to-floor junctions in occupied precast concrete (PC) and reinforced concrete (RC) apartment buildings with different exterior wall systems. Three representative PC apartment buildings with different exterior wall systems were investigated under winter nighttime conditions. IRT was used to qualitatively assess thermal bridge characteristics in all three buildings, while the in situ thermal performance of one representative case was quantitatively evaluated by estimating the effective thermal transmittance (U-value) from infrared surface temperature measurements based on heat transfer theory. The estimated U-value was validated using three-dimensional heat transfer simulations. The results showed that exterior wall-to-floor junctions were major heat-loss pathways in all cases, while the thermal bridge patterns varied depending on the exterior wall system and continuity of insulation. In Case 3, the PC curtain wall system with improved insulation continuity exhibited less pronounced thermal bridging than the corresponding RC system. The IRT-estimated Ueff was 0.379 W/m2·K for the PC building and 0.661 W/m2·K for the RC building, representing a 42.7% lower value for the PC building. The corresponding simulated values were 0.407 and 0.514 W/m2·K, with differences between the IRT-estimated and simulated values of 7.4% and 22.2%, respectively. These findings are expected to provide useful baseline data for post-occupancy performance assessment and improvement in envelope design for off-site construction (OSC)-based PC residential buildings.