  A lot of current buildings are operated energy inefficient and offer a great
potential to reduce the overall energy consumption and CO2 emission. Detecting
these inefficiencies is a complicated task and needs domain experts that are
able to identify them. Most approaches try to support detection by focussing on
monitoring the building's operation and visualizing data. Instead our approach
focuses on using techniques taken from the cyber-physical systems' modeling
domain. We create a model of the building and show how we constrain the model
by OCL-like rules to support a sound specification which can be matched against
monitoring results afterwards. The paper presents our domain-specific language
for modeling buildings and technical facilities that is implemented in a
software-based tool used by domain experts and thus hopefully providing a
suitable contribution to modeling the cyber-physical world.
