Passive House refurbishment facade with integrated photovoltaic modules for direct, current-based warm water preheating. The GIWOG, an energy-conscious and environmentally and socially oriented client, intends to undertake an energy-related modernisation project, which will further optimise energy consumption to be more efficient at an apartment complex in Graz, main street 302-306. The goal is to lower the energy consumption for heating and hot water from the current level of approximately 135 kWh /m²a to approximately 8 kWh /m²a. The planned measures should correspond with an overall energy consumption reduction of approx. 94 %.

Short Description




The current energetic properties of the residential complex are at the level of 1978-1979, ie, with non-insulated walls, a myriad of extreme heat bridges, a central gas-fired heating system and electricity driven boilers for decentralized production of hot water; features which all correspond to the normal standard of residential buildings in the 1980s.

The final energy consumption for heating and hot water can be lowered from the current level of approximately 135 kWh /m²a to about 8 kWh /m²a through the modernisation of the system - this corresponds to a total energy reduction of approx. 94 % (95 % for space heating, hot water for about 45 %).

This is achieved by:

  • the use of a special superior gap solar facade that comes with pre-function panels (passive solar honeycomb panels) and a safety glass plane as the outer skin
  • with decentralized ventilation units with heat recovery and façade-integrated photovoltaic modules for the DC-based hat water heating
  • as well as generously sized balcony window surfaces of passive house quality

The present project should carry out a wide range of functional tests, especially with the new approach of using locally generated solar power in the building compound with a primary focus on building integration (facade-integrated photovoltaic modules), the achievement of a high degree of prefabrication as well as the low-tech approach (DC based hot water heating, i.e. no inverters, no power supply, no counters. The proof of the efficiency of the energy system should be provided with appropriate monitoring.

Project Partners


Bmst. Ing. Mayrhofer Otmar Gemeinnützige Industrie- Wohnungsaktiengesellschaft


Contact Address

Bmst. Ing. Mayrhofer Otmar
Welser Strasse 41, A-4060 Leonding
Tel.: +43 (050) 8888 142
Fax: +43 (050) 8888 197