A modern concept for office buildings: energy saving and good indoor climate are no longer contradictory.

An up-to-date design concept for office buildings results in a very low energy consumption and provides a better indoor climate at the same time. This new concept is based mainly on two design features: An extremely well insulated building envelope decouples the indoor climate from the outside climate to a high degree during all seasons and weather conditions. The second element of this new design concept is the HVAC-system: The source-dominated displacement ventilation provides a better comfort and, as a cosequence of its high effectiveness, is very economical. Normally windows are the thermal leaks of the building envelope. In order to overcome this deficiency, Geilinger Ltd in Winterthur, Switzerland developped the High Insulation Technology (HIT). Typical glazing-U-values are around 0.65 W/maK. The consequences on natural air flow and on the energy balance are enormous: radiator heaters are not anymore necessary in a HIT room and the air change rate of a mechanical ventilation can be reduced considerably compared to the requirements of conventional air conditioning installation. Modern office buildings usually produce considerable internal loads (occupants, lights, computers, office equipment) which compensate the heat transmission losses in winter. In summer, the excellent insulation protects the building from outside heat during the day. A t night free cooling can be used. Measurements of energy consumption and investigations on thermal comfort were made at different HIT-buildings. One case is presented in this paper.