Keywords:Passive façade, Low-Tec, energy efficiency, adaptive façade, performance gap, adaptive g-Value
In times of energy use awareness, decarbonisation, and resource efficiency, the performance of well-known façade components must be pushed beyond current limits through innovative designs and new combinations in construction. This paper presents an unconventional redesign of a double skin façade (DSF), based on Trombe wall principles, to enlarge solar gains in heating seasons and avoid overheating issues in summertime. The DSF variant is equipped with a thermal storage mass in the DSF cavity and interior insulation. The thermal mass, in this case concrete, is of a dark colour for high solar absorption, whereas the shading device is highly reflective. In contrast to traditional Trombe wall systems, this TCW is not supposed to actively heat interior space or transfer thermal energy. Instead, the TCW aims to regulate heat flux within the façade level by the management of solar thermal energy fluxes. The potential to reduce buildings’ heat losses through solar energy use is shown and compared to a traditional external thermal insulation composite system (ETICS) with an appropriate insulation thickness for renovation purposes in Switzerland. The U-Value is therefore considerably lower, 0.25 instead of 0.41 for the TCW. Due to the innovative design and fully transient operation, a highly detailed and flexible simulation tool is needed to analyse and assess the façade performance. The decision to simulate the novel system was made for Modelica-Dymola, with its object-oriented, equation-based simulation language. The simulations of both TCW and ETICS show potential for heat loss reduction due to solar energy storage on every orientation. However, the TCW shows a high solar energy usage due to its ‘natural’ overheating tendency. Furthermore, heat losses are significantly lower than the U-Value predicts and, in some cases, even lower than the ETICS heat losses. In addition, due to its lower use of material and lower weight, the system can be used as a curtain wall system instead of traditional DSFs, which have higher heat losses in winter and higher solar gains in summer.