Abstract
There is an obvious and indisputable need for an increase in the efficiency of energy utilization in buildings. Heating, cooling and lightning appliances in buildings account for more than one third of the world's primary energy demand. In turn, building stock is a major contributor to energy-related envirnomental problems. There are great potentials, which can be obtained through a more effivcient use of energy in buildings. A careful look at the exergy flows in buildings and the related supply structures, similar to other thermodynamic systems such as power stations, can help identify the potential of increased efficiency in energy utilization. Through the analyses, it can be shown that calculations based on the energy conservation and primary energy concept alone are inadequate for gaining a full understanding of all important aspects of energy utilization processes. For example, the high potential for a further increase in the efficiency of boilers whose energy efficiency is close to 100%, can not be quantified by energy analysis alone, but it can be shown by using exergy analysis, the exergy efficiency of a common gas boiler is about 8%. This paper outlines the international co-operative work in the general framework of the International Energy Agency Energy Conservation in Buildings and Communities Systems (IEA ECBCS), the: Annex 49 "Low exergy systems for high-performance buildings and communities" (Annex 49 2007).