Greenhouse effect.

This office and workshop complex for a small town in Germany perfectly illustrates that country's concerns with the imaginative, beneficial use of ambient energy to improve the wellbeing of building inhabitants.

The Works Department of the small city of Ettlingen near Karlsruhe in Germany enjoys an unusually pleasant site, on the edge of the town, looking southeast towards the far-off ridge of the Black Forest. The architects have taken advantage of a relatively large plot, and arranged the accommodation on its north and west sides, releasing the south and east borders so that the buildings can overlook the magnificent forest views.

Planning strategy is layered. A long two-storey block rules off the north edge of the site. To its south, there is a linear double-height greenhouse, and to the south of that, workshops project into the green space at right angles to the main west-east axis. Each of these elements is joggled as it were from left to right, so that the upper level of the two-storey block is projected westwards to act as a porch to the public entrance. The west end of the glasshouse acts as the public entrance hall, protruding through a long curved wall that runs roughly north/south up the site, cutting the public front garden off from the vehicle aprons, and from the green swarded south-east sector of the site where radial rows of ornamental cherry trees emphasise the view over the forest. Moving east beyond the curved wall, the drum of the cafeteria is the notional centre of the composition. Beyond that, are the single-storey workshops with their north-facing monitor lights and wide separating access gangways which are flooded with light from continuous curved transparent roofs. The remaining major element of the composition, the big garage for municipal vehicles, is set on the east side of the curved wall, and its own outer curve emphasises the importance of the cafeteria as the focus of the complex.

From the approach road - Hertzstrasse, which defines the site to the west - the thrusting end of the administration block draws attention to the building (and incidentally provides a place from which all visitor and staff movements can be monitored). The great grey curved wall, set (too?) far back from the street is perforated by openings which give framed glimpses of the work areas and the pretty lawns and trees in the south-east sector of the site.

The public entrance itself is though the west end wall of the greenhouse. The scale of this glass expanse is ameliorated by the dextrous use of a layer of elegant thin hardwood slats which provides a degree of shading from the sun, and a welcome moment of small detail. Once inside, a long sunny space unfolds below. (The site falls so that the long administrative block is in effect a half storey higher than the level of the workshops and the greenhouse's long garden.) As yet, the planting has not grown to its full extent, but it is easy to see that the place will be splendidly luxuriant and a pleasure to be in and look onto.

The cafeteria pokes into the corner of the interior garden, and the two storeys of offices in the administrative block look down onto the space, and out through it to the Black Forest. Automatic canvas blinds shade its windows when the sun becomes too intense, but the climate of the glasshouse itself is modified in several ways. The top of the slope is shaded with wooden slats like those over the public entrance. The remainder of the inclined plane of glass can be shaded by translucent velaria. At the top of the section is a north-facing clerestory which is opened automatically when the temperature in the glasshouse becomes too great. Panes at the top of the vertical south-east facing glass wall are opened automatically too, so causing a convection current upwards under the glass roof, which draws overheated air out from the body of the conservatory.

In winter, the glasshouse is heated by the sun and waste energy from the offices, cafeteria and workshops, so its overall impact on the energy budget is beneficial and at the same time it provides an amenity which visitors as well as office and workshop staff can enjoy. The marginal increase over normal in atmospheric oxygen that its plants produce is supposed to make people in the building happier and more efficient. Perhaps it does, but the experience of looking across the conservatory to the Black Forest is so transfixing that everyone in the building must be happier than in an ordinary workplace. Whether that leads to greater productivity, only time will tell.