Analysis of nonresidential building structures shows that many are characterized by high energy consumption. Administrative/office buildings and production and maintenance facilities pose specific challenges to those seeking improved energy management and building energy performance. Questions of energy consumption in these buildings are generally seen as secondary to the improvement of comfort and/or functionality. This is most pronounced within the existing building stock. Decisions to retrofit a building are often made because of dissatisfaction concerning the comfort level or as a consequence of changes in building use or in processes performed in the building. The primary goal of the retrofit is to improve these conditions. Good technologies to meet this end are currently available. The objectives of the International Energy Agency Energy Conservation in Buildings and Community Systems (ECBCS) Programme Annex 46 (IEA 2011a) is intended to provide tools and guidelines to identify energy conservation opportunities in buildings and to improve the indoor environment of these buildings in energy-efficient retrofitting projects. Among the tools developed by this project is the Energy and Process Assessment Protocol, which provides an energy assessment methodology and procedure suitable for different types of sites, including a variety of different nonindustrial buildings with energy requirements dominated by climate, and industrial buildings with high energy loads dominated by internal processes and high ventilation requirements per floor space. This paper presents the energy assessment methodology for a single building or a large building stock, along with examples of typical energy wastes and inefficiencies in different types of buildings and typical processes.