Saving resources and cutting costs, protecting the environment and using renewable energies are the criteria which are important for modern buildings, and as such, designers today face the complex challenges of "integral planning", demanding the interaction of various disciplines to create a building with optimum efficiency whilst saving material and running costs. Active factors such as construction, buildings skins, layout of rooms, and exterior space should take up as little of the internal technical units as possible and all passive measures should be exploited to the maximum.