The classical exergy analysis enables to pinpoint the location, to understand the cause, and to establish the true magnitude of waste and loss. Exergy analysis is therefore an important tool for the design of thermal systems since it provides the designer with additional information on where and why the losses occur. The designer can then proceed forward and work on how to improve the thermal system. Application of exergy analysis into buildings has not been usual before the implementation of Annex 37. Tools for exergy analysis of buildings were developed during the working time of Annex 37.
Exergy analysis can also be applied to human body to find optimal thermal conditions. Studies show that the lowest human body exergy consumption occurs at thermally neutral condition. Exergy consumption within the human body becomes higher in a cold environment due to larger difference in temperature between the human body and its surrounding space and also becomes higher in a hot environment mainly due to sweating. These findings suggest that heating and cooling systems may also work well in such conditions where the lowest amount of exergy is consumed by those systems. That is, we may be able to establish both thermal comfort and low-exergy consuming systems at the same time. The human body exergy analyses have now just started to articulate why LowEx systems are essential for creating rational and comfortable built environment.
There are currently many LowEx technologies available. Low temperature systems successfully combine both traditional and innovative new approaches to heating. Usually the heat is transferred into the room through air or liquid circulation systems and the same system can often be used for both heating and cooling.
Research shows that people living in houses with low temperature heating systems are very satisfied with ambient indoor air quality. In particular, thermal comfort levels are considered to be higher than in houses with a traditional heating system. Residents also experienced a reduction in draughts and dust, and reported fresher air in houses with low temperature heating systems. The advantages and disadvantages, mentioned by the occupants in the survey conducted during Annex 37, are similar to results in the literature. Also experiences from the case studies supported the findings from literature and the occupants' survey.
By using low temperature heating systems the room temperature can be decreased by a few degrees, which is more energy efficient and healthier for occupants. Low temperature heating systems do not usually require radiators, which can be unsightly and hard to clean. This offers the additional advantages of increased living space and more flexibility in terms of interior design. Safety can also be improved during the heating season due to absence of hot radiator surfaces.
Low temperature heating systems are sustainable because they are flexible. These systems are not bound to any one energy source and fuel switching does not entail excessive cost. Low temperature systems can utilise a variety of sources of heat including district heat, biofuel, solar energy, gas, oil or electricity, and so the user is not constrained by choices made in the planning phase.
Thorough planning and expert implementation are prerequisites for an appropriate and functional system. System flexibility will be dependent on the choice of appliances and overall system design, which can be difficult and expensive to change after installation.
Low temperature heat distribution systems have an operating life of at least 30-40 years during which time the user benefits from the economic advantages offered by flexibility of fuel choice. The life cycle costs of a low temperature heating system are about the same as of a traditional system. Although the initial investment might be slightly higher, the system offers increased flexibility in terms of fuel choice and increased energy efficiency. For example the efficiency of solar heating is considerably higher in a low temperature heating system than in a traditional one.
The demonstration projects of Annex 37 show the wide variety of possibilities to apply low exergy heating and cooling systems in buildings. There are examples of low exergy systems in dwellings and offices, but also in a museum and a concert hall.
The application of LowEx systems provides many additional benefits besides energy supply such as: improved thermal comfort, improved indoor air quality and reduced energy consumption. These aspects should be further promoted to increase the application of LowEx systems for heating and cooling of buildings. The building regulations and energy strategies should take the quality of energy into account more than today.
Wide application of LowEx heating and cooling systems in buildings will create a building stock, which will be able to adapt to use of sustainable energy sources, when desired. Without this ability, the transfer towards an energy-wise sustainable world will be delayed for decades.