Modelling Life Cycle Cost for Indoor Climate Systems

Abstract: The indoor climate system, which serves a building with a proper indoor air quality and thermal comfort, has been predominantly designed based on the initial cost. A life cycle approach could improve both the economic and environmental performance since the energy use could decrease. There has been a lack of knowledge, models and tools for determining the life cycle cost (LCC) for an indoor climate system. The objective of this research project is to propose a model and a PC program for calculating the LCC for indoor climate systems. Focus is on indoor climate systems in Sweden for premises and dwellings. This thesis presents the LCC model and addresses some questions about input data and indoor climate system design through seven appended papers. The indoor climate systems included in the LCC model have different principles for supplying air, extracting air, recovering heat, controlling the airflow rate and supplying heating and cooling to the building. The LCC includes initial costs for purchasing and mounting the components. The LCC also includes running costs for energy, maintenance and repair. Space loss due to indoor climate system components is taken into account in the form of an annual rent loss. A work productivity cost related to ventilation airflow rate and indoor temperature can be added. A scrap value can also be added. According to LCC techniques, all future costs are discounted to the value of today, which is the net present value method. Some results from the PC program implementation in its present state are given. The results from the LCC model can help to choose the system with the lowest LCC for a particular situation. The results can also help to focus the development of indoor climate systems on parameters that are the most important to get systems with lower energy use, which can help to reach the environmental aims of society. In the future, verifications and refinements of the proposed LCC model hopefully will take place.