The German firm LOG ID always uses south-facing conservatories to achieve a green, solar architecture. On the south side, they admit sufficient solar heat for subtropical plants to flourish and allow the users to benefit fully from sunlight during the winter.

[Research Laboratory for Experimental Traumatology, Ulm, Germany]

[indoor garden of Research Laboratory for Experimental Traumatology, Ulm, Germany]

This is not however necessary possible in an urban infill project such as the library and cultural center in Herten.  The architect Dieter Schempp therefore place an air collector which juts out on all sides on top of the building volume. The collector functions as a heat exchanger and warms the air that is pumped into it. Some of this air comes from the building interior: all stale air except that extracted from the kitchens and toilets passes through the glazed rotunda into the space between the glass roof and the building. The subtropical plants in the rotunda filter the air and enrich it  with oxygen. When the building does not require heating, the stale air exits the building through a bypass. In these circumstances, the air-filled collector functions as a thermal buffer and blocks a significant amount of solar heating. Solar collectors are mounted between the glass upper roof and the building roof to provide hot water.

[Glasshouse, Herten, Germany]

The glazed Rotunda serves as a meeting place and concert auditorium. It is noteworthy that no acoustic damping material was required in this glazed hall because the plants proved sufficiently sound-absorbing. The 'solid' part of the structure contains the library.

[interior of the Glasshouse, Herten, Germany]