Assessment of thermal performance and surface moisture risk for a rear-ventilated cladding system for façade renovation

Abstract

Ventilated façade systems, incorporating thermal insulation behind a rear-ventilated cladding, constitute a popular renovation solution in warm European climates. For compliance with building regulations, their energy efficiency is usually obtained through simple onedimensional desktop calculations, which do not consider the impact of the support elements of the cladding penetrating the thermal insulation. This study assesses a ventilated façade system anchored over a solid concrete wall with adjustable stainless steel brackets. One-dimensional calculations are compared against three-dimensional numerical thermal modelling, evaluating the effect of insulation thickness (40-100 mm) and potential gaps in the insulation around anchors. Results indicate low risk of condensation and mould growth over internal surfaces. The additional heat flow induced by stainless steel anchors, which is not considered by simplified calculations, appears lower than for aluminium-based systems but can become significant as insulation levels increase. Ensuring the continuity of insulation around anchors is critical for keeping this additional heat flow at reasonable levels (8-13%). If gaps in the insulation are present around anchors, the additional heat flow increases substantially (25-70%) and pushes effective U-values above 0.4 W/m2K, thus resulting in unforeseen energy consumption and non-compliance with regulatory requirements in many European locations.