The notion of quality is complex in the building sector because of the variety of functions that installations need to fulfil1, such as providing a space suitable for carrying out diverse activities, with given comfort conditions, protecting possessions and people, managing relationships with the outside, projecting an image, etc. The quality criteria concern different technical areas (e.g. structural mechanics, acoustics, lighting, heat transfer) as well as more subjective areas (e.g. aesthetics, quality of life, comfort).