Abstract
Ventilated façade systems have become an interesting solution in the field of energy efficiency for buildings thanks to their associated improvement in thermal insulation properties. However, differences exist between real and theoretical thermal performance, resulting in an increase of actual energy consumption above predicted values. Part of this mismatch can be attributed to thermal bridges both at support elements and at construction junctions, which are usually overlooked by simplified calculations. The present study assesses the potential for substituting metallic elements with polymeric composite materials for two key elements of ventilated façades: the support subframe of the external cladding and the external window reveals. Thermal, structural and durability properties are specifically assessed. Results show that overall heating energy savings between 7 and 13% can be obtained through the use of pultruded composite profiles at support brackets and window reveals instead of aluminium components. Such solutions are feasible from a mechanical and durability point of view, and the extra costs are offset in a short period through the reduction in heating expenses.
Highlights
The improvement of the thermal insulation properties of building envelopes is widely recognised as one of the most efficient interventions for improving the energy efficiency of buildings, becoming a key measure on the road towards Nearly Zero Energy Buildings (NZEB) [1]
Results show that overall heating energy savings between 7 and 13% can be obtained through the use of pultruded composite profiles at support brackets and window reveals instead of aluminium components
The desktop study described in this paper has demonstrated that the partial replacement of metal elements with polymeric composite materials brings a significant improvement of the thermal performance of ventilated façade solutions
Summary
The improvement of the thermal insulation properties of building envelopes is widely recognised as one of the most efficient interventions for improving the energy efficiency of buildings, becoming a key measure on the road towards Nearly Zero Energy Buildings (NZEB) [1]. The main objective is the reduction of thermal bridge heat loss, by locally replacing a material with very high thermal conductivity (λ = 160–230 W/mK) by polymeric composite materials with much lower conductivity (λ = 0.1–0.7 W/mK) This replacement would result in a reduction of the overall heat flow across the façade (and an improvement in overall energy efficiency), but mechanical response and durability need to be considered. 3. Thermal performance assessment An assessment has been carried out to calculate the reduction in heat flux across a ventilated façade obtained by replacing aluminium elements with polymeric composite materials. The improvement is highest for the L-shaped support brackets: if these elements are made of pultruded composite, the additional heat flow can be considered negligible (< 3%) and the material choice for the T-shaped vertical profiles becomes almost irrelevant regarding heat transfer
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