Using VPN technology for networking intelligent building automation via the Internet

In modern times, when climate change is getting more and more drastic and issues like CO2 emission and energy efficiency are becoming more and more important, it is necessary to find possible energy savings in every area. To achieve these possible savings also in the residential area it is essential to establish Intelligent Building Automation in residential buildings. Therefore, within the framework of a research project, two apartment buildings are equipped with the field bus KNX, which is used i.e. for control of heating, ventilation and lighting to realize an energy-efficient habitation .In the field of heating alone savings up to 50% of energy are to be expected [1]. For the intelligent control of the buildings a facility server is needed. But this will not only manage one apartment building but several simultaneously, and thus linking them together. To test this concept two KNX-Networks were connected with each other by two apartment buildings through the Internet using a virtual private network connection.