Fast characterization of wall thermal performance via enhanced Hot Box methodology

Accurate thermal characterization of building envelope components is essential for energy-efficient and climate-resilient design. Conventional hot-box testing requires separate and prolonged procedures to determine steady-state (U-value) and periodic thermal properties, resulting in high experimental time and energy demand. This study proposes an enhanced hot-box methodology combining two sequential tests within a single campaign: a first response-factor-based dynamic test using triangular temperature excitation to determine the U-value without full steady-state convergence, and then, a sinusoidal periodic test to identify thermal transmittance, decrement factor, and time shift. The procedure was validated on a lightweight insulated wall and a high-inertia masonry wall. Uncertainty propagation and optimization of excitation parameters were considered. Under optimized configurations, the dynamic method determined the U-value within ±4.0% of the steady-state reference for both wall typologies, while reducing testing time by up to 50% and energy consumption by up to 34%. For the massive wall, accurate results required careful tuning of excitation amplitude and test duration to avoid response truncation. Periodic thermal parameters were successfully identified and showed limited sensitivity to measurement noise. The proposed sequential framework enables integrated evaluation of steady-state and periodic properties with reduced experimental load. The method is reliable under controlled boundary conditions and appropriately selected excitation parameters, while high-inertia assemblies require careful tuning to ensure accuracy.