The building stock accounts for between 16 and 50 percent of national energy consumption worldwide [1–3]. Governments around the world are thus rolling out energy directives, national regulations and energy-efficiency labels that set minimum requirements for buildings' performance [4], and promote the construction of green buildings [5]. Buildings' stakeholders have thereby started dealing with buildings as products-with-services rather than just simple products. Services may for instance include energy monitoring or equipments' maintenance during a building's use-phase. Moreover, new market expectations such as the 'energy performance contracts' have started to emerge in a number of countries [6]. Such services and offers require thus a better control of performance's variability during a building's lifecycle. Consequently, a better comprehension and consideration of the key determinants of energy performance has become essential for the design and marketing processes of buildings. Occupant behavior is a substantial source of uncertainty in energy modeling since. It can impact energy consumption by as much as 100% for a given dwelling [2,7–14]. Industrial energy simulation tools such as Energy Plus and eQUEST propose some simplifications regarding occupants' behavior (among other simplifications), which may lead to unrealistic energy estimates, and may eventually be one of the reasons behind high discrepancies between predicted and real energy consumption values [15–18]. Nowadays, such performance discrepancies are no longer tolerated-especially in the case of green (energy-efficient) buildings. More precise methods are therefore needed to model occupants' influence on buildings' energy performance. Such models should result in more accurate energy estimations, and hence improve building designs and marketing offers. The authors have proposed an activity-based model of residential energy demand (SABEC, standing for Stochastic Activity Based Energy Consumption) in a doctoral dissertation [19]. The present paper is not intended to detail the model, but it briefly recalls the adopted modeling methodology. The main focus here is to show how a user-focused model, which accounts for occupants' energy-related needs and activities, can be used within the engineering design, energy management processes, and marketing offers of residential buildings. 2 Book's title A literature review is first presented followed by a brief recall of the proposed modeling methodology and a sample of simulation results. The possible integration of the proposed model into the design and energy management processes of residential buildings is then demonstrated through a number of use cases.