Passive Cooling Strategies - Low Energy Cooling for Sustainable Buildings - page 65

Figure 3.4 Low-energy office building in Freiburg, Germany

3.1.3 Low-energy Office Building in Freiburg

The Solar Info Centre (SIC) in Freiburg is a new office building for renewable energy
companies (see Figure 3.4). Therefore great care was taken to obtain an energy-
efficient building.
The net floor area is about 14 000 m 2 , distributed over six floors in the northern and
western wings and three floors in the eastern wing. The outline is U-shaped. The gross
room volume amounts to about 58 000 m 3 ; 45% of the fa¸ade is glazed. The building
is connected to a district heating system from the neighbouring university hospital
power plant, assisted by solar collectors. To obtain a neutral CO 2 balance, a CO 2
trading investment was made in a highly efficient heat recovery systemof the hospital's
power plant which saves more energy than the SIC building needs. Mechanical night
ventilation supplies the required cooling energy, drawing cold ambient air through
open flaps in the fa¸ade and rejecting the warmair over the roof. The night air exchange
rate is 2 h − 1 from 22:00 until 06:00 in the morning. The fans are only operated if the
ambient air is 3 K below room temperature and a minimum cooling power of 116 kW
is achieved.
Located on the first floor is a seminar room with a floor area of 170 m 2 . Air-
conditioning of this room is achieved by geothermal energy. Five vertical borehole
heat exchangers of 80 m each supply cooling and heating energy. This system is
designed for a cooling load of 16 kW. The fan is capable of generating a volume flow
of about 5100 m 3 h − 1 .

3.2 Passive Night Ventilation Results

3.2.1 Internal Loads and Temperature Levels

Two office rooms in the Lamparter building were analysed in detail: on the south-west
side of the building a 20 m 2 office is occupied by two persons with one computer