An energy-hungry old apartment complex was renovated to meet the German passive house standard. A special solar façade made this possible for the nonprofit housing firm GIWOG.

Old buildings can be real energy hogs and an ecological nightmare. “There must be a better way,” thought Georg Pilarz, Alfred Willensdorfer and Johann Aschauer.

They pondered how to make an energy wonder out of an old, energy wasting building while assuring high comfort and low costs. On a cold winter day Johann Aschauer had an inspiration: “I was so fascinated by the warmth of the sun’s rays on my skin that I had the idea of heating with light. The idea was implemented with a special solar façade. The secret resides in the special cellulose webbing that resembles a honeycomb: The low-lying winter sun penetrates the honeycomb structure and heats it, while the high summer sun creates cooling shadows.

Thus the solar façade achieves a year-round perfect climate zone and thereby collects enough energy to provide hot water. A large storage tank ensures that the heat is available when it is needed; on demand, a secondary ground heat pump system is available. A ventilation system with heat recovery provides hygienic fresh air.

GIWOG AG is proud of the project, which passed its trial by fire last winter: The required heating energy and the associated CO2 emissions dropped to 10% of previous values! This serves as a model for millions of old apartment buildings and is an environmentally friendly prototype.