Performance assessment of a “do it yourself” double skin green façade for an existing office building

Abstract

This project is based on two sustainable construction methods, namely up-cycling (reuse of materials) and vertical farming (green facades). These two concepts are combined to form a ‘Do It Yourself’ double skin façade, a double skin façade made with re-used sliding doors, which is aimed to be capable of developing ‘Edible Green’, which refers to the placement of edible vegetation in the façade of an office building. As two sustainable methods are combined into one project, the investigation of the performance of this ‘Do It Yourself’ double skin façade arose as an objective. Hence the aim of this research was to investigate the climatic performance of the façade for the growth of plants, as well as its influence in the indoor environment of the office. The façade was divided into 6 modules across two floors, capable of accommodating vegetation individually. These modules were assigned different design strategies based on ventilation, shading system, watering system and the placement of plants. Five different types of plants were placed on each module. Three types of ventilation strategies were adopted as parameters for the modules, namely minimally ventilated, naturally ventilated and mechanically ventilated. The configuration of plants were such that all modules had a total of 9 plants, with 7 short growing and 2 tall growing plants. The watering strategy was adopted in the form of drip irrigation system, where the modules in the top floor received constant rate of irrigation whereas the modules in the bottom floor received varied rate of irrigation. A measurement system was developed using a microcontroller, namely the Arduino UNO. The parameters were evaluated by the placement of measurement sensors in each of the modules. The measurement was done over a period of three weeks where the temperature, relative humidity, illuminance, CO2 and Total Volatile Organic Compounds (TVOC) were measured. The obtained values were studied and analysed based on the expected behaviour from the literature. The condition of the plants in the cavities were evaluated by determining the yield produced by each of the module, and also by a visual inspection of the plants. It was observed that the plants play an influential role in increasing the humidity in the cavity, especially in the cavities of the non-ventilated modules. This was evaluated by comparing the relative humidity and absolute humidity of all the modules. It was found that the humidity in the minimally ventilated modules was higher compared to the rest. Moreover, it was found that the shading in the façades highly influence the temperature in the cavity. The performed experiments suggested that the use of plants in the double skin façade, along with an external shading strategy can decrease the temperature in the cavity by up to 13°C and can increase the relative humidity of air in the cavity by 38%. Moreover, the experiments with respect to mechanically ventilated modules show that the cavity preheats the air by up to 6°C during night time and pre cools the air by up to 10°C during high outdoor temperatures (summer afternoons). Based on the theoretical and real time evaluation, it was concluded that the minimally ventilated modules perform relatively better with respect to the condition of the plants, whereas the mechanically ventilated modules perform better with respect to the indoor environment in the office. However, the influence of the double skin façade alone on the indoor environment of the office could not be determined, as there were external influences on the climatic conditions inside the office building. Based on the results, a design strategy was successfully formulated and the performance of each module was investigated. The research answered the question with respect to maintenance of the double skin façade for the growth and health of the vegetation. Moreover, the research helps to provide ideas on different design strategies that can be used, based on different sustainable design requirements.