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. Such standards are developed within ISO/TC 163.ISO/TC 163 has produced a large number of test and calculation standards by which the thermal(energy) and hygrothermal performance of a wide range of materials, products, components orelements and the whole building can be established.During the last decades, the thermal insulation of new buildings has been greatly improved, resulting inconsiderable lower needs for heating. In many countries, the use of electricity in buildings hasincreased enormously. Therefore it has become more and more important to take the total energy useof buildings into consideration. Therefore, the new scope of ISO/TC 163 covers not only the energy forheating and cooling but also the energy used to operate the building and its technical building systems.