Coupled numerical model for the thermal simulation of PCM-integrated envelopes and controlled night ventilation

Abstract

Computational analysis of building envelopes incorporating phase change materials (PCMs) constitutes a key strategy for passive design and thermal stress mitigation in warm climates. However, under severe summer conditions, such materials can suffer thermal saturation if nocturnal latent heat discharge is not promoted. This work presents a multi-component coupled (1D–0D), transient, continuously differentiable numerical model to evaluate the thermal response of rooms with PCM-integrated envelopes, incorporating a controlled natural night ventilation strategy. To avoid numerical noise and oscillations inherent to discrete controls (ON/OFF thermostat type) during the explicit update of room air within a staggered coupled scheme, a continuous sigmoidal regularization is proposed for the ventilation flow. Heat transfer within the envelope is solved implicitly using the finite element method (FEM) under a mixed temperature–enthalpy formulation, coupled with the resolution of the indoor air balance. Results demonstrate that mathematical regularization stabilizes the room calculation and facilitates an accurate evaluation of the dual benefit of this strategy: it provides direct sensible cooling of the air and favors the extraction of latent heat stored in the walls, collectively mitigating indoor thermal deviations relative to the established upper limit.