Fener, a new Radiance-based building energy model, is presented. The motivation is to be able to perform detailed analyses of complex fenestration systems (CFS) from the energetic and daylighting points of view. The model couples daylighting and thermal simulations in a time-step basis, so that shading control strategies that depend on thermal variables, such as indoor air temperature and energy load, can be simulated without iterating between full-year simulations of a thermal model and a daylighting model. Fener is a "shoe-box" energy model that uses the three-phase method and bi-directional scattering distribution functions (BSDF) to predict the transmitted solar irradiance and indoor illuminance of office spaces with CFS. The model can also be used as a shading controller simulator, whose output in terms of shading operation can then be used in standard building simulation programs.