With the introduction of THEWOSAN the city of Vienna has created an exemplary instrument of thermal and energetic retrofit of large-scale housing schemes of the 1950s - 1980s.

After an appropriate time span of intense use we analyzed current and finished projects in order to suggest means of optimization of the subsidy and at the same time securing a high livel of retrofit quality and environmental sustainability. This results in a range of suggestions regarding extents and variation of the subsidy, energetic and thermal measures to be taken to qualify for the subsidy, social factors, ecological quality.