Passive Building Air Conditioning
Impermeable surfaces such as roofs and streets influence the urban microclimate by impacting on the radiation or energy respectively. As a result, ambient temperatures surrounding buildings also rise and lead to a room climate of discomfort or increased energy use for air conditioning. One solution to this problem is to green their façades and roofs, thereby consuming heat energy through evapotranspiration.
Measurements taken at two roofs in Berlin-Tempelhof show that 58% of the radiation balance can be converted into evapotranspiration during summer months.
In comparison, non-greened roofs can convert 95 % of the radiation balance into heat. Façade greening can even more significantly impact on a building’s energy balance. The average evapotranspiration rate between July and August was between 5.4 and 11.3 millimetres of water per day depending on the respective floor, i. e. an average cooling value of 157 kWh per day
Energy balances of an extensiv greened roof and an asphalt roof, daily mean, measured from June to August 2000.
Click on the images to enlarge.