Untitled Document

Roofed internal garden

The IBN building's most significant innovation must be the versatile, active role the roofed interior gardens play in controlling the interior climate. In winter, the interior gardens act as building insulation and a heat source: in summer, they function as a sun break and natural air conditioning. They bolster the level of thermal insulation of the building to such an extent that it was possible to make sixty-five percent of the area of the office wing outer walls of clear double glass. Relatively little artificial lighting is consequently needed the office wings.

In wintertime
The energy equation of the internal garden is a surprisingly simple one. In wintertime they function during the day roughly as normal greenhouses. The glass roof over each garden reduces heat loss from the inward-facing walls of the offices and laboratories, and at the same operates as a large solar collector. Sunlight enters through the glass and warms the air in the internal garden, which then flows into the building via the windows and sliding doors of the garden-facing walls. Adjustable sunblind on the inside of the glass roof are closed at night. The heat-reflecting foil on the sunblind and internal accumulated by the building and internal gardens during the day from escaping by radiation at night.

In summertime
In the summer, the internal gardens operate in the reverse way to the above. The adjustable sunblind are closed during the day to help keep the internal gardens as cool as possible, and opened at night to allow the buildings and internal gardens to cool off as much as possible by nocturnal ventilation and radiation. The natural draught causes fresh air to be drawn in from the relatively cool north facade through the crawl space under the laboratory wing. In the internal gardens, this fresh air undergoes further cooling by evaporation: the roughly six thousand liters that evaporates daily from the leaf surfaces of the vegetation in the internal gardens and from the surfaces of the pools and watercourses provides a cooling capacity of about 20 kilowatt-hours - enough to lower temperature of the ventilation airflow by several degrees. The cooled air is moreover naturally humidified by the evaporated moisture.

Concrete skeleton

The concrete skeleton of the building plays an important part in controlling the in the interior climate. The thermal mass of the exposed concrete plays a part in the natural cooling system as a temporary store of heat or cold. The concrete absorbs some of the heat produced in the interior during the day by the sun shining through the windows, the bodies of the staff, artificial illumination, computers and other electrical appliances. The absorbed heat is expelled at night by ventilation through openings in the glass roofs and the staircases, leaving the structure ready to absorb heat again in the morning. This night cooling system is obviously inactive in periods of the year when heating is required.

In highly office buildings such as the IBN, much more energy can be saved by efficiency in cooling than by efficiency in heating. The latter is only required on cold winter days but there is a heat surplus for most of the rest of the year. The combination of natural ventilation, evaporative cooling, night cooling and external sunblind does more than save energy, however. Expensive, maintenance-sensitive cooling installations could be dispensed with. The absence of air conduits and lowered system ceilings made it possible to suffice with a constructional height 30 centimeters less than normal for office floors. This in itself yields an energy economy, besides saving building materials. At the same time, the absence of a lowered ceiling makes the office spaces 20 cm taller than usual.