Design aspects of a ventilated facade with integrated photovoltaics - Evaluation as a refurbishment solution for office buildings inSweden

Abstract: Swedish office buildings of the 60’s present at least 27% higher heating demand than from the current standards foreseen. This underlines their need for energy renovation. Meanwhile, office buildings are occupied during daytime, thus internal and solar gains are in phase. Consequently, such buildings could experience overheating problems. A seasonal adaptable envelope, such as a ventilated double skin façade, can be a potential improvement to both, heating and cooling issues of office spaces. At the same time, EU regulations imply that by 2020 all buildings should produce the energy they consume, on an annual basis. This energy should come from renewable sources. Solar electricity systems linked to buildings are often integrated in building envelopes. However, the electricity conversion efficiency of these systems decreases with increasing temperature. In the first part of this thesis the aim is to examine the critical design parameters of a ventilated façade with integrated photovoltaics, and analyze its impact on the thermal performance of a typical cell office with a 60’s envelope, located in Southern Sweden. Investigations are focused on the energy use and the thermal comfort quality of the room and they are performed for two window-to-wall ratios and four orientations. In the second part of the work, the focus is given on evaluating the effect of the cavity’s ventilation on the PV’s efficiency and annual energy production. The study concluded that an upgrade to a ventilated double skin façade can yield a decrease of 30% to 60% on the energy use of a typical cell office, achieving the current requirements. The lowest energy use is attained through a low emittance external glazing combined with a reflective shading. The integration of solar cells does not lead to an overall improved performance compared to a case without photovoltaics. The cavity ventilation resulted in a maximum increase of 6.5 % on the solar cells’ efficiency, but the increase of the annual electricity output is at maximum 2% and was considered negligible.