A design process perspective on the energy performance of buildings

Sammanfattning: From a sustainable development perspective, buildings should be designed to be as energy-efficient as possible, as the contribution of buildings to total energy consumption has steadily increased, reaching between 20% and 40% in the developed countries. One of the main challenges for achieving this goal is to develop more cost-effective systems and processes for energy renovation and modernising of the building stock of Europe. This challenge is addressed in this thesis. The research presented herein has had the overall purpose to identify and explore obstacles in the design process of constructing more energy-efficient buildings. Three research questions have guided the research work: (1) How can life cycle cost be used to predict the cost benefits of energy efficient buildings?; (2) How can the handling of energy performance requirements in the design process for buildings be improved?; (3) How do client requirements, political governance and regulations affect the design of energy performance in buildings? The research is based on literature reviews, interviews and surveys, as well as case and computational studies. A computational study was performed with three different building types situated in Finland using three different energysaving design concepts for each building. Energy consumption and construction costs were analysed for each case and the financial viability was analysed using the discounted payback method. Individual interviews were carried out to determine to what extent life cycle cost calculations are used in the construction sector and how energy performance is taken into account in model-based design processes for buildings. A decision-making framework and an axiomatic design model for a performance-based design process was then developed and the conceptual model was compared with a real case of low energy design in Sweden. Finally, a survey explored energy conservation strategies in the design of buildings in Germany and Sweden and a longitudinal investigation of key policy instrument regarding energy conservation in Germany and Sweden was conducted to support the main findings of the survey. The main results of the research work show that: ' There is no evidence that the design of energy performance is considered differently in the design process for buildings in Sweden and Germany, even if regulations and building codes differ between the two countries. However, the somewhat steeper reduction in space heating in Germany compared with Sweden could be due to the stricter regulation in the building codes in Germany over the last decade. ' The transparency of the design and the associated decision-making about energy performance can be improved by using the requirement management model developed, which is based on axiomatic principles and the proposed decision-making framework for evaluating, structuring and detailing the requirements from the conceptual to the detailed design stages. ' Energy performance design can give cost benefits over a specific time for a building, as measured by the resulting life cycle costs. In general, life cycle cost analysis can be a tool for evaluating cost benefits over time and provide support for the decision-makers, but the challenges and uncertainties of its use have to be taken into account in the decision-making process. To conclude, the "energy gap" between regulations and what is technologically possible can be reduced to a certain extent by facilitating the energy design process with a performance-based design process and decision-making tools that support the evaluation of life cycle performance. However, it seems that regulation is a more important driver for the development of technology for low energy housing than market forces so the regulatory limit should therefore be set with respect to what is possible and not with respect to current practice.