Velux’s Model Home 2020 project involves creating a series of show homes meeting the European Commission’s 2020 energy efficiency requirements and proving that only slight increases in construction costs are needed to achieve significant energy savings and high comfort levels. Sunlighthouse is the third house in the project, but Austria’s first carbon-neutral single-family home. It was designed by Hein-Troy Architects and can be found outside Vienna in Pressbaum on a relatively shady hill, facing south east overlooking the surrounding woods. Creating this three-storey house involved taking into account the position, and studying the orientation and layout of the volumes so as to maximise sun exposure and optimise daylight and energy. Since the mountains cast plenty of shadows in the valley, the living area also has roof windows that allow light to enter from above. The kitchen and dining areas are on the south east side, with light from numerous roof and facade windows. This solution not only provides stunning valley views, but also maximises sunlight. Inside, windows account for about 36% of the net floor area of Sunlighthouse, drastically cutting the need for daytime artificial lighting. All the windows are low-emission electric windows with an external pane (4mm), an Argon-gas spacer (14.5 mm) and, for the inner pane, laminated safety glass (6.4 mm). The automated io-homecontrol® system ensures the windows are opened and closed in relation to the weather, guaranteeing ideal ventilation for spring, summer and autumn. In winter, Sunlighthouse uses a forced ventilation system with heat recovery, while in summer cooling is a combination of the stack-effect created by the windows, night-time ventilation and external blinds on the windows. The house has a heat pump to heat the home, solar collectors to produce hot water and photovoltaic panels to generate power. Together, these aspects reduce consumption and achieve a positive energy balance. Calculations shows that, over 30 years, Sunlighthouse will not only use less resources than it produces, but it will also have produced as much clean energy as was used in its construction, thus making it a true zero-emission building.