Maintaining Comfortable Summertime Indoor Temperatures by Means of Passive Design Measures to Mitigate the Urban Heat Island Effect-A Sensitivity Analysis for Residential Buildings in the City of Vienna

The waste heat generated from the use of air conditioning systems in cities significantly contributes to the urban heat island effect (UHI) during the summer months. Thus, one of the key measures to mitigate this effect is to limit the use of active cooling systems. In the city of Vienna, air conditioning units are common in nonresidential buildings, but have so far been much less installed in residential buildings. This is mainly due to the fact that the Viennese summertime climate is still considered to be relatively comfortable and planning guidelines related to energy efficiency are already strict, resulting in high-quality buildings in regard to thermal performance. However, during the last decade, an increase in summertime temperatures and so called tropical nights has been recorded in Vienna and subsequently the postconstruction installation of air conditioning systems in residential buildings has significantly increased. In a study undertaken for the City of Vienna, a series of passive design measures have been simulated with current and future climate scenarios in order to determine the most effective combination of architecturally driven actions to avoid the use of air conditioning systems in residential buildings whilst maintaining comfortable indoor temperatures.