# 1. Introduction¶

This user guide explains the use of the Modelica library BuildingSystems (http://www.modelica-buildingsystems.de), which is being developed for the dynamic simulation of the energetic behavior of single rooms, buildings and whole districts.

One important part of the library consists of an adaptive building model, which is able to adapt its spatial resolution (0D, 1D, 3D modelling approach) and also its physical model (e.g. pure thermal or a hygro-thermal calculation) to the respective problem of the simulation analysis.

**0D modelling approach**: The adaptive building model works in a strongly simplified and abstracted configuration
(low-order or gray box model), which leads to numerically fast calculations. A typical case study is the
simultaneous calculation of the thermal energy demand of a large number of single buildings of a district
in combination with a district heating network (compare with Figure 1.1).

**1D modelling approach**: In this case the adaptive building model uses more spatially resolved algorithms and models
and also more simulation time for a single building. A typical application is multi-zone-building models,
which calculate the heating and cooling energy demand, the air temperatures and air moistures for each thermal zone as well as
the air exchange between the single thermal zones of a complex building. The Rooftop building in Figure 1.2, for example, has
two air-conditioned and two not air-conditioned rooms, so it could be modelled with four thermal zones.

**3D modelling approach**: The most advanced configuration consists of a spatially resolved room model,
which describes the three-dimensional air flow within a room volume, the geometrical long-wave and
short-wave radiation distribution and also the multidimensional heat transport within the building construction.
For example, this model is able to calculate the location-dependent thermal comfort within a room (compare with Figure 1.3).

The BuildingSystems library supports pure thermal or also hygro-thermal calculations for all three modelling approaches. Mixed thermal and hygro-thermal simulation analysis and different spatial resolutions for different zones of a building model are also supported.