Dynamic performance assessment of multilayered wall assemblies

Abstract

This paper introduces an approach to assessing the dynamic performance of multilayered building envelopes, focusing on physically measurable thermal performance metrics. Based on EN ISO 13786:2023, the study considers thermal transmittance (U-value), internal areal heat capacity (k1), and decrement factor (f) as thermal performance parameters, and wall mass as an additional objective indicator. Five wall assemblies common in the Ukrainian market - hempcrete, AAC + Rockwool, Porotherm brickwork + Rockwool, wood-chip cement-bonded blocks (Woodcrete) and ICF systems were evaluated through numerical modelling and comparative analysis. To eliminate subjectivity in the weighting of criteria, the four physically meaningful parameters are compared to determine the overall assessment. Results indicate that Wall E (ICF) ranks as the dynamically balanced, efficient assembly according to the internal area heat capacity and decrement factor parameters, but it has the maximum mass among other assemblies. Wall B (AAC) demonstrated the highest heat-flux attenuation effect, 0.115, which can lead to summer overheating, while Wall C (hollow brick + insulator) and Wall D (Woodcrete) demonstrated a similar dynamic behaviour with a too-low decrement factor, 0.007. The study highlights the complexity of MCDA in envelope design and provides physically grounded criteria that can support more objective predesign decision-making. Current research revealed that, even though all the walls meet the requirements of the Ukrainian National Building Code, steady-state thermal transmittance coefficient (U-value) can be considered only in the early stages of decision-making as the primary determinant of envelope efficiency; however, this parameter alone fails to accurately reflect the dynamic thermal behaviour of constructions and their inertia-related performance.