kab Architekten - Fellbach Mnchen Shanghai

kab Berner & Partner design office building with a modular air-conditioning concept

The glass facade protrudes from the building like half a barrel lying on its side and creates a foyer area of great transparency.
 The light flooded entrance area belongs to the administration and design centre of the Hoffmann + Krippner company in Buchen. The special feature of the building: The transparent building can do largely without mechanical ventilation even in the hot summer months thanks to a sophisticated air-conditioning concept. The Fellbach architects’ office kab Berner & Partner is responsible for the technically and structurally progressive building.

Aim: To make mechanical air conditioning superfluous

The specification for the building project was to create a particularly motivating working environment. The generous flooding with daylight was especially important – brightness after all stands for transparency and well being. Despite the large glazed area and the associated heating of the rooms during the summer months, however, a mechanical air-conditioning system is to be dispensed with in most of the rooms. “We want to find new solutions for ecological, economical and medical reasons,” says Max Hoffmann, Managing Director of Hoffmann + Krippner.

“We have to install air conditioning“, was the categorical statement of the ventilation engineer. An opinion that Frank Berner, Managing Director of kab Berner & Partner, was unwilling to accept without contradiction. He and his team developed a ventilation concept in several points which provided for both the use of natural thermionics and the use of shade giving and evaporation cooling plants.

Ventilation with a suction effect

The building owes the greatest cooling effect to a sophisticated air circulation. The air flows in through lamellas at the foot of the building and rises up due to heating as in a chimney. It draws off newly produced heat as it flows past the windows. The heated air finally escapes through vents on the top of the building. “The upward moving air acts as a screening curtain,” architect Berner sums up, “so that the air-conditioning concept exploits natural thermionics.”

For the event that normal thermal currents are hardly available – for instance under heavy low pressure weather conditions – fans have been installed in the hatches. These are there to help along the thermal currents. However, these devices have not had to be used yet because the interaction of the other air conditioning components provide adequate cooling.

Since the ventilation wing is burglar-proof they can also be left open when there is no-one in the building. In this way it is possible to use the cooler night air for controlling the temperature of the building. All the technical components of the concept work fully automatically: Storm and rain sensors control both the incoming and outgoing hatches and the activation of the fans for example.

Natural support: Plants as cooling units

The foliage makes a contribution to the overall concept: Trees on the outside are not only a decorative element but also constitute biological protection from the sun. They offer shade in the summer and therefore cooling, in winter, when they have shed their leaves, they support the supply of light to the building. “In this way we integrated the natural principles in our concept“, says architect Frank Berner. 

Two metre high Ficus trees dominate the interior. A species with small leaves was purposely chosen to increase the total surface area. “Water evaporates through the surfaces of the leaves and provides a cooling effect,“ company head Hoffmann reports, “one tree consumes up to 70 litres on hot days.“ In addition to the evaporation cooling, the plants draw off additional heat to be able to perform photosynthesis.

Innovative material against the greenhouse effect

The sun protective glazing acts like sunglasses for the building. The special glass suppresses the transformation of short-wave light beams into long-wave heat radiation, in other words – the greenhouse effect. This enables a reduction in radiation of 20 percent. But the material is still designed to allow heating of the interior in winter.

It was originally planned to evaporate a reflective coating onto the inside of the windows additionally. This should provide extra protection against the sun. However, the high effectiveness of the other air conditioning details meant that this measure could be omitted.

Insulation and shading as a temperature regulator

All outside components of the building are highly insulated in the unglazed places. The insulated walls keep out heat in summer and ensure that stored heat cannot escape in winter. 

The blinds of the building are controlled automatically by summer sensors. Contrary to normal practice the basic setting of the blinds is closed when the sun is shining. Of course the users in the offices can adjust the shutters to suit their individual requirements.

The principle is reversed in the winter months. The ventilation openings stay closed and the sun blinds open so that the sparse winter light can penetrate deep into the building and make a passive contribution to its heating.

Adapted user behaviour for a greater feeling of well being

“People feel temperature differently in summer, wear lighter clothing and drink more,” architect Berner explains. “At 36 °C in the shade an indoor temperature of 28 degrees is considered pleasant.“ The planners therefore assumed in their concept that extremely cooled rooms which cause goose bumps even in summer could not be the answer. They relied rather on an adapted user behaviour. 

“We had slightly increased temperatures in the rooms last summer,” Hoffmann reports. “But they did not exceed 26 degrees and were not uncomfortable.” This satisfied the specification not to completely level the temperature curve occurring over the day but simply to make it flatter.

Ecological concept with economic benefit 

“Doing without technical components totally in modern buildings is virtually impossible,” architect Berner days, “intelligent planning can, however, reduce the percentage drastically. This means seeing the use of technology not as a compensation for poor planning but as a final optimisation of a sophisticated concept.

In the few artificially air-conditioned rooms such as conference rooms, telephone exchange and canteen the necessary cooling performance is therefore low. “The running costs for the 400m² equipped with air conditioning amount to approximately 3,500 Euro“, Max Hoffmann reports. Projected to the remaining area of 1,300 m² without mechanical air-conditioning this means a cost saving of more than 11,000 Euro a year.
Now, after five years in use and a very hot summer, the building owner has gathered enough experience to sum up. “The concept has paid off to our total satisfaction in terms of cost and effect,” says owner Max Hoffmann. Hoffmann + Krippner’s new building project is also being planned and implemented by kab.