The client for the project has a long standing interest in building sustainability developed through working at the Sustainable Energy Development Authority (SEDA). With this interest in mind, the client approached CHROFI to design a house that would demonstrate a number of active and passive sustainable initiatives whilst accommodating a contemporary coastal lifestyle. The project is situated on the south side of Mona Vale Headland and has expansive views over Mona Vale Beach to the south. This south facing aspect and the narrow site proportions combine to limit the passive design potential and accordingly establish the key design challenge for the project. Our response orients the house toward the view to the south, but opens up the roof at the centre of the house with a large north-facing skylight to admit winter sun to the south facing living areas. This traps and holds the warmth of the winter sun using the thermal mass of the structure.