The space heating concept of the self-sufficient solar house Freiburg

Even on overcast winter days, the solar radiation flux on vertical house walls exceeds the conductive heat flux outwards through the walls which is caused by the temperature difference between indoors and outdoors. On transparently insulated house walls the insolation even on such days can be utilized to compensate for the conductive heat losses and to serve as an effective direct solar space heating system. The Self- Sufficient Solar House (SSSH) which is going to be built in Freiburg is heated with a solar fraction of more than 90% by such a wall with Transparent Insulation (TI). The space heating demand of the SSSH is reduced to 300 kWh/a ( 2 kWh/qm heated living area) auxiliary heating energy. The optimal ground-plan for the SSSH was found to be a sector of a circle. This shape gives the best ratio between north oriented walls with energy losses and the south oriented TI wall. The energetic optimization of the SSSH was done by computer with the simulation program HAUSSIM. This prog ram has been developed to simulate the new TI wall heating system. The TI wall heating system is combined with other measures to minimize heating energy demand. Windows with a U-value of 0.6 W/(qmK), opaque wall insulation with U smaller than 0.2 W/(qmK) and an air ventilation system with highly efficient heat recovery are the main components.