Integration of demand networks into dynamic building energy models. Mechanisms of plant component heat transfer and heat loss have a large impact on building energy consumption and thermal comfort. With regard to a satisfying detail level, geometric information must be considered: the pipe or channel installation inside the building, the layer structure of pipe sheath and the location of the plant component inside the room or the room enclosing. The article focuses on integrating such models into a dynamic simulation with a high geometric detail level. The equations lead to large sparse systems, and the numerical solution of the balance equation and the coupled algebraic equations must be implemented in an accurate and efficient way. We introduce suitable algorithms and implementations.