Towards Lean Buildings - Examples and Experience from a German Demonstration Program for Energy Efficiency and Solar Energy Use in Commercial Buildings

The paper presents the description and initial evaluation of a number of commercial large scale buildings situated across Germany. The study has been carried out within the framework of the demonstration program SolarBau, which has been initiated and funded by the German Ministry of Economy and Technology. The program funds up to 25 demonstration buildings and their collective evaluation. Funding is only provided for the design of the buildings – for increased energy-related planning and simulations and for thorough monitoring after construction. The absence of investment subsidies ensured that all design solutions were realized under representative economic boundary conditions. The technical requirement for admittance of a building to the program is an anticipated total annual primary energy use (heating, cooling and lighting) below 100 kWh per m2 net floor. These ambitious goals can be reached advantageously by a so-called lean building featuring increased thermal insulation, intensive use of daylight and a strategy for passive summer cooling. The reduced HVAC system relies heavily on a building with appropriate design for the given climatic boundary conditions. In the moderate German climate, the focus for commercial buildings lies on the avoidance of unwanted solar gains in the summer. The internal loads can mostly be counterbalanced by increased utilization of the thermal inertia of the building combined with nocturnal ventilation or supplementary earth-to-air heat exchangers for pre-cooling of the building`s supply air.