As the United States moves toward increasingly higher-efficiency buildings, some cities are reaching that goal in Europe.

The city of Aachen, Germany, calls itself “the ecological city of the future,” and with good reason. It boasts one of the most energy-efficient office buildings in Germany, in which its energy costs are 80 percent lower than those in a similar building.

The Balanced Office Building, or BOB, was created as part of a low-energy construction program managed by the German Federal Ministry of Economics and Technology. The SolarBau program aims to demonstrate the feasibility of highly energy-efficient buildings for nonresidential purposes, with an emphasis on energy optimization.

SolarBau said its objective is to demonstrate a series of pilot projects with a total primary energy demand for each building for HVAC and lighting purposes below 32 kWh/m²a (an amplified means of payment associated with solar designs). To achieve this, the buildings integrate passive and active solar designs, advanced HVAC systems, and innovative thermal insulation.

SolarBau includes 25 pilot buildings throughout Germany and an accompanying evaluation program that measures their energy use.


BOB’s design team wanted to create an energy-efficient office building that could be cost-effectively built and operated. This was achieved by the combination of renewable resources and advanced control systems.

“We decided on LonWorks because this technology could realize perfect producer-independent integration,” said Christian Obst-Moellering, systems and development engineer at Enervision, the system integrator. The system fully integrates HVAC and lighting.

This control technology is an open, extendible architecture that lets control devices from multiple manufacturers interact with each other. The system also collects data on energy consumption, which is analyzed for energy optimization and further research on the building.


BOB minimizes energy use by constantly optimizing system functionality. This was achieved through an intelligent combination of optimized thermal insulation that activates storage mass for heating and cooling, and automatically controlled lighting that maximizes the use of daylight.

Underground probes, controlled by the building management system, tap stored geothermal resources for heating and cooling. This is combined to work in conjunction with small ventilation units.

An external forecasting service supplies meteorological information to the control system, creating an advance-response system that helps the building automatically prepare for weather changes.

The entire system is controlled and monitored over a single Web server, Enervision’s GateOn, which enables remote monitoring 24 hours a day.

Thanks to the network infrastructure, which is built upon a vertical fiber optic backbone, the system is easily expandable. For example, installing the building’s security system, which took place after construction, was a matter of adding devices to the existing backbone.


BOB’s energy monitoring system lets SolarBau researchers access data on the building’s energy use for further study and optimization. Results thus far have been positive.

Although the winter under examination was very cold and the following summer reached record high temperatures, the building’s energy savings were well above target. Its HVAC and lighting costs were 80 percent lower than those in a similar office building.

Another goal of the BOB project was to make sure tenants enjoyed a high degree of comfort and flexibility with regard to the control system; the system should, in fact, be virtually invisible to them. In a survey after the summer of 2003, 97 percent of the employees said they were satisfied with the building’s cooling system.

Publication date:01/29/2007