Some weeks ago, the Empress Court was completed. This office building was proclaimed an exemplary building in 2007 by the Brussels Institute for the Environment. Actually, this project is a renovation of the Telex-building, as it is known in Brussels.

The Telex-building was built in the '60s by architect Léon Stynen, for the Public Service of Telephony and Telegraphy. The renovation project consisted of transforming the building to an office space for the rental market. The difference with other large real estate projects in Brussels, is the fact that the existing potential of an existing building in the city centre is being used, taking advantage of public transport, instead of choosing for a new construction on the periphery.

That same ambition for sustainability stimulated flexibility, in order for the future end-users to be able to occupy the building as optimal as possible. Already in 2007, VK proposed a pioneering energy concept, making it earn the title of exemplary building. The energy needs of the building were optimized, while guaranteeing the comfort of the end-users.

FACADE RENOVATION WITH RESPECT FOR THE EXISTING SITUATION

One of the great challenges was renovating the envelope to a higher level of performance, with consideration for the historic value of the architecture. The most performant concept in this context was the integration of a single sheet of glass on the inside of the facade, creating a double skin. Through an opening on the bottom and extraction on top, the double skin was mechanically ventilated by the air that is exhausted from the room. This results in multiple advantages:

• possibility to install mobile solar protection between the 2 sheets of glass
• in summer, the heat that is accumulated in the double skin, is evacuated directly by the ventilation system
• in winter, the heat of the exhausted air is recuperated by energy recuperation on the central ventilation group. As such, heat is recuperated while maintaining the local comfort.
• a strong reduction on cold radiation. The surface temperature of the inner glass depends mainly on the climate in the double skin, not on the outer temperature
• the acoustical performance of the facade is enhanced, not unimportant for a building in the city centre
• the internal facade modulation is separated from the modulation of the existing facade, enhancing the possibilities for the interior arrangement.

HEAT RECUPERATION BY COOLING CEILINGS

The offices are cooled by means of a cooling ceiling, a system that functions with high temperatures. During the intermediairy seasons, with outer temperatures between 5°C and 12°C, it is not exceptional for a building with likewise dimensions to have to be cooled in certain areas, depending on the orientation. In this project, the water of the cooling ceilings, after they have absorbed the heat of the rooms, is used to preheat the outer air.