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Keywords: model validation

Experimental determination of heat losses through cracks in building walls

https://doi.org/10.58224/2618-7183-2026-9-5-5
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Abstract
This study investigates how a repaired crack affects heat losses through a building envelope. An experimental setup was designed and assembled to test wall specimens containing a crack repaired by injection grout. A calculation procedure was developed to determine the specific heat loss through the repaired crack under the conditions of the proposed experimental apparatus. The experimental data were statistically processed using the Shapiro-Wilk test to assess normality. Differences in the specific heat loss before and after crack formation were evaluated with the paired Student's t-test. Statistical significance was accepted at p < 0.05. All statistical analyses were carried out in IBM SPSS Statistics. Tests were carried out on foam-concrete, clay brick, and reinforced concrete specimens. Ten speci-mens were prepared for each material under investigation. During the first stage, intact specimens without cracks were tested. Afterwards, an artificial crack was introduced into each specimen, repaired by injection grouting, and the specimens were tested again under identical conditions. The measured results showed a statistically significant increase in heat loss after crack repair. On average, the specific heat loss increased by 12.1%. The experimental findings were compared with numerical simulations. The temperature field around the repaired crack was calculated by solving the two-dimensional steady-state heat conduction equation. Robin (third-kind) boundary conditions were assigned to the external surfaces exposed to air, Neumann (second-kind) boundary conditions were specified at the truncated boundaries of the computational domain, and fourth-kind boundary conditions were applied at material interfaces. Numerical simulations were performed in ANSYS Workbench 2024. The difference between the numerical predictions and the experimental measurements did not exceed 2.1% for foam concrete, 3.8% for clay brick, and 2.4% for reinforced concrete. The results demonstrate that even after repair, wall cracks noticeably affect the thermal performance of building envelopes. The proposed mathematical model can therefore be used for numerical assessment of heat transfer in walls containing cracks repaired with injection grout.
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Experimental evaluation of the thermophysical performance of an adaptive composite wall system under dynamic climatic conditions

https://doi.org/10.58224/2618-7183-2026-9-1-8
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Abstract
In the sharply continental and hot climate of Kazakhstan, improving building energy efficiency requires adaptive composite envelope systems capable of dynamically responding to external thermal loads. This study provides experimental validation of a newly developed adaptive energy-efficient wall assembly with alternating air channels and a radiant barrier, previously proposed and numerically investigated by the authors. The experiments were conducted in a climatic chamber using a full-scale 3×3 m wall fragment under two operating modes: cold conditions (–14.3 °C) and hot conditions (+26.4 °C with exterior cladding heated up to +46 °C). Interlayer temperatures, heat flux density, and thermal bridging in the bracket zone were measured, and both calculated and effective thermal transmittance resistance values were determined in accordance with regulatory requirements. The experimental results demonstrated strong agreement with numerical simulations: deviations in interlayer temperatures did not exceed 3-7%, while heat flux density differed by 6-9%. The wall configuration Scheme 3/50/75/50 exhibited pronounced adaptive behavior; switching to the ventilation mode during the hot period reduced heat flux density by up to 14% and decreased the temperature gradient within the air channel by an average of 3-5 °C. Under cold conditions, the system increased thermal resistance by up to 18% compared with assemblies without a reflective layer. The obtained effective thermal resistance values comply with the building standards of the Republic of Kazakhstan and confirm the energy efficiency of the wall system for operation in extreme climates. Overall, the experimental validation confirms the reliability of the model and the high practical applicability of the adaptive wall technology. The findings provide a scientifically grounded basis for the development of façade design standards optimized for Central Asian climates and demonstrate the potential for implementation in both new construction and retrofit projects.
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