Regional climate is an important element in architectural design. In particular, passive design that uses natural energy effectively by architectural methods is getting its importance from the viewpoint of environmental problems and energy conservation. The slender sites existing as a typical housing lot offer various requirements for the contemporary urban house. Especially, ambivalent necessities emerge for window such as privacy and view, getting brightness and warmth in winter. This paper aims to clarify characteristics of spatial composition, light environment and thermal environment near the window of contemporary Japanese houses in the slender site during winter.