Life cycle cost optimization of buildings with regard to energy use, thermal indoor environment and daylight

Buildings represent a large economical investment and have long service lives through which expenses for heating, cooling, maintenance and replacement depends on the chosen building design. Therefore, the building cost should not only be evaluated by the initial investment cost but rather by the life cycle cost taking all expenses in the buildings service life into consideration.

Also the performance of buildings is important as the performance influences the comfort of the occupants, heating demand etc. Different performance requirements are stated in building codes, standards and by the customer. The influence of different design variables on life cycle cost and building performance is very complicated and the design variables can be combined in an almost unlimited number of ways.

Optimization can be applied to achieve a building design with low life cycle cost and good performance. This paper discusses performance optimization and outlines an optimization method based on minimization of the life cycle cost constrained by performance requirements. Many different performance requirements can be included in the optimization.

The performance requirements discussed in this paper are heating demand, thermal indoor environment and daylight. To illustrate the optimization method it is applied to performance optimization of an office room. The example shows that optimization is a valuable tool in the building design process.