Energy simulation and life cycle costs estimation of a building's performance in the early design phase

Abstract: Sustainable development and the protection of the environment are key issues in our society today. The building stock in Europe accounts for over 40% of the final energy consumption, CO2 emissions and generation of waste. A large part of the life cycle performance is determined early. Investigations show that when 1% of the project costs are spent, roughly 70% of the lifecycle cost of the building has been committed indicating that decisions taken early greatly affect the life cycle performance. The building's shape, selected materials, structural system, internal room distribution, and building services systems are some of the most important factors that influence the environmental and energy performance of a building throughout its lifecycle. The objective of the conducted research was to investigate what kind of energy analyses are possible to carry out in the early design phase to give the decision makers a more holistic view of the energy performance of a building over its life cycle. Three research questions have guided the research work; (1) What types of energy simulations are possible to make in the early design phase? (2) How reliable are early energy estimations compared to results when detailed models are available? (3) How does energy consumption affect the life cycle cost of a building? The research work is based on literature reviews, a theoretical framework for model based design of life cycle aspects in general and energy performance in particular developed in the European Union sixth framework project InPro. The study includes a number of energy performance calculations at different levels of information maturity in the early design phase. Different energy simulation programs were used for this purpose. The study was performed for an existing building where design parameters like window area, building envelope and indoor climate been changed. In total 28 cases were analysed using four different energy analysis tools at three levels of information maturity. The resulting life cycle costs were also estimated for the different cases with varying rates of interest and forecasts of the energy price. The result of this study shows that energy calculations usable for design decision can be made at different levels of information maturity. Depending on the maturity level more or less detailed design information is available which influences the estimated energy consumption. Therefore early estimations when the information maturity is low should only be used to compare different design alternatives at the same design stage. However, the result shows that these early estimations can give a clear tendency guiding the design in a more energy efficient direction. When the information maturity is higher and indoor climate simulations are possible to make at room level, the result gets more accurate. However, the use of more sophisticated energy simulations tools is time consuming and error prone since the amount of input data needed is much higher. This calls for better integration between the design and energy analysis especially when more advanced energy simulations are performed.  The resulting life cycle costs of the different cases are strongly affected by the estimated energy consumption, the selected real rate of interest, the forecast of energy prices as well as the discount time. The conclusion of this study is that energy calculations are usable for the decision making of design alternatives in the early design phase. Also, life cycle cost estimates can support the decision makers in the analysis of different financial scenarios.