Timber solar facade: A responsive façade for the refurbishment of existing buildings

The increasing use of highly energy efficient façades is becoming a real asset in the building market as well as the adoption of lightweight constructions and low environmental impact materials. The research is here focused on timber lightweight envelopes, describing, on one hand, a new concept of timber façade system, based on a responsive behaviour and specifically developed for retrofitting purpose and, on the other hand, the long term monitoring activity aimed at testing its thermal performance. Façade concept starts from a responsive approach for building skins aimed at reducing the heat flows crossing the façade under different boundary conditions. The façade under test presents a naturally ventilated cavity hosting a cardboard honeycomb or cork material. During winter the building envelope can be used as a solar collector, exploiting solar radiation crossing the external glazing and trapped inside the cavity which is thus collected by the honeycomb structure. In order to avoid overheating, during summer, solar heat gains are partially removed through the naturally ventilated gap. In this paper, results of the optimization process on a first prototype of the façade, carried out through an experimental campaign in outdoor test cell and on a demo building, are presented, focusing on both thermal and acoustical aspects. The thermal performance has been investigated through temperature profiles during different seasons and under different configurations. As far as the acoustic performance is regarded sound insulation and reverberation time on the demo building, have been assessed. The built-up of the façade system on a wood prefabricated demo building allowed to face all the aspects related to the whole construction process and to evaluate the envelope performance under real operating conditions