Optimization of buildings with respect to energy and indoor environment

The purpose of this project is to develop a building design methodology that supports optimization of building designs in the early stages of the design process. The purpose of building design optimization is to reach a cost effective building design with good performance. This means that the optimal building design in a given case must fulfill requirements expressed by the society and the user of the building at minimal cost.

The evaluation of cost is based on life cycle cost calculations and the optimization is performed with respect to other performance aspects such as energy use, indoor environment and daylight conditions. The design methodology is developed based on a discussion of the building design process, performance assessment methodologies, modeling and simulation of buildings, economic theory and optimization approaches.

Many aspects of the overall building performance depend on decisions in the early stage of the design process. To improve the performance of buildings it is necessary to be able to assess the performance and monitore cost during the design process. This is possible if the consultants and the building user cooperate with the contractors, manufacturers and suppliers from the early stage of the design process.

The desired performance of the building is based on an early identification of the needs expressed by the user and the society. Many aspects related to the physical, energetical and environmental performance of a building design influence the life cycle cost. Therefore, the life cycle cost may be used as an objective measure of the overall building performance.

Still aspects such as thermal indoor environment and daylight conditions are difficult to associate directly with cost. These aspects must be handled individually by imposing additional performance requirements. Performance assessment of different building designs requires the use of computer simulation.

With few exceptions, existing design tools may be used to evaluate the consequences of a particular building design but are generally unable to suggest a particular design solution. Using design tools, problem definition and parameter variations can be very time consuming. Also analyzing many parameter variations may not result in the optimal solution, as the influence of different design parameters on the performance can be difficult to understand.

Automatic optimization can replace manual variation of different design variables and save the building designer a lot of work and at the same time guide the building designer towards a cost effective building design with good performance. In this thesis a building design methodology is suggested that support optimization of building designs in the early stage of the design process.

The design methodology is implemented in a design tool that utilizes an optimization method to perform automatic parameter variations of the design variables to find the geometry and mix of building components that minimizes the life cycle cost with respect to energy use, thermal indoor environment and daylight conditions.

The building designer defines the geometric parameters, selects alternative building components from a building component database and defines performance constraints that constitute the solution space for the design problem using a graphical user interface. The design methodology implemented in the prototype tool is tested on two case studies.

The case studies consider optimization of a room in a one-family house and optimization of office rooms in a multi storey office building. Based on the work presented in this thesis it is concluded that is possible to develop design tools that are useful in the early stage of the design process and helps the building designer minimize the life cycle cost of the building design with respect to energy and indoor environment.