This paper summarises the work of the LowEx co-operation /1/. The aim was to promote rational use ofenergy by encouraging the use of low temperature heating systems and high temperature cooling systems ofbuildings. These systems can use a variety of fuels and renewable energy sources. Energy is used efficientlywhile providing a comfortable indoor climate. Exergy defines the quality of energy and is a concept fordesigning and assessing different heating and cooling systems. Application of exergy analysis into buildingshas not been common before. Low exergy systems are defined as heating or cooling systems that allow theuse of low valued energy as the energy source. In practice, this means systems that provide heating orcooling energy at a temperature close to room temperature.Low exergy systems successfully combine both traditional and innovative new approaches. Research showsthat people living in houses with low exergy systems are very satisfied with indoor environment quality. Thedemonstration projects, in turn, show the wide variety of possibilities to apply low exergy heating and coolingsystems in buildings. The Guidebook, which was the final product of LowEx cooperation, is meant to helpengineering offices, consultants and architects in their search for energy efficient heating and coolingsystems that can provide the occupants with comfortable, clean and healthy environment. In addition, somebackground information is offered for real estate builders, building maintenance managers, political decisionmakers and the public at large.