The IB is normally defined in terms of BA, OA, security system, information processing and telecommunications services However, the buildings being already in existence are deficient in two areas. One of these areas is building envelope and plan. The other area is mechanical, electrical and structural systems which do not provide the environmental quality required by IB. Existing technology and design knowledge are available to address these deficiencies. Especially, the office buildings being already in existence must meet IB requirement in order to achieve desirable office environment. They are a building envelope, moisture control, properly-located windows, shafts for duct, telephone and electric closets and acoustical environments. In this paper, a new approach to construct the work scope of remodelling the office building being already existence is described by contrasting the building performance criteria of IB. It concludes by speculating on the consequences of extrapolating the results of study to remodelling the office building being already existence.