buildings

There is an obvious and indisputable need for an increase in the efficiency of energy utilisation inbuildings. Heating, cooling and lighting appliances in buildings account for more than one third of theworlds primary energy demand. In turn, building stock is a major contributor to energy-relatedenvironmental problems.

The International Organization for standardization (ISO), Technical Committee 163 "ThermalPerformance and Energy Use in the Built Environment" (ISO/TC 163) is dealing with development oftools that can be used to design and construct or retrofit energy efficient buildings and installations. Theoverall aim for this is to reduce our dependency of non-renewable resources and to reduce theemission of harmful substances to the air. Methods are needed for the evaluation of the energyperformance of complete buildings and parts of buildings or building installations.

The present paper deals with modeling of various low-exergy system components and their integrationinto the energy system for buildings and small communities. The exergy content of a certain amount ofenergy is defined as the part of this energy that can be used to produce mechanical energy. The qualityof a certain amount of energy is defined as the relative exergy content of this energy. Most of ourbuildings with their heating and cooling systems today are built for conversion of high quality energysources to low quality use with a huge destruction of the available exergy as a result.

Methods are needed for the evaluation of the energy performance of complete buildings and parts ofbuildings or building installations. In order to arrive at energy efficient buildings, materials and productsthat effectively contribute to the thermal performance of the building and its installations must be used.For that standards dealing with the design and evaluation of materials, components and systems playan important role.

The application of system identification techniques to the energy performance assessment of buildings and building components requires a high level of knowledgeof physical and mathematical processes. This factor,combined with the quality of the data, the descriptionof the monitoring procedure and test environment, together with the experience of the user of the analysis software itself, can produce varying results from differentusers when applying different models and software packages.

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.

The European Research Area (ERA) in the field of energy in buildings continues to develop dynamically in response to both the market needs and to the ongoing technological and legislative developments. Various networking mechanisms can be applied by key actors in the field to enhance access to research activities and increase the coherence of the scientific community: one such mechanism was formulated in the early 90s by the grouping of research actors from the PASSYS and PASSYS II research and technical development projects funded in part by the European Commission.

The existing buildings stock in European countries accounts for over 40% of final energy consumption in the European Union (EU) member states, of which residential use represents 63% of total energy consumption in the buildings sector. Consequently, an increase of building energy performance can constitute an important instrument in the efforts to alleviate the EU energy import dependency and comply with the Kyoto Protocol to reduce carbon dioxide emissions.

The application of system identification techniques to the energy performance of buildings and building components requires a very high level of knowledge of physical and mathematical processes. This factor, combined with the quality of the data, the description of the monitoring environment and procedure, together with the experience of the user of the analysis software itself, can end up in varying results from different users when applying different models and software packages.

In cold and moderate climates, improvements in building shell insulation and air-tightness imply a shiftin heating loads from transmission and infiltration towards ventilation. Heat recovery from the ventilation airflow plays an increasingly important role in minimising energy needs. Such heat recovery systems rely on the input of electric power (to drive fans, heat pumps, etc.) in order to recover thermal energy. Since electricity input is relatively small compared to the amounts of thermal energy recovered, such systems are efficient from an energy viewpoint.