Steep and spectacular, the Sunlighthouse rises from a mountainside near the Austrian capital of Vienna. With its asymmetric design, straight lines and pale-wood cladding, the house seems both modern and organic. So do the ideas behind it.

The design, created by Juri Troy of Hein-Troy Architekten, was a direct response to the home’s surroundings. The Sunlighthouse resembles a rock on the mountain, but the high-rise construction is less about achieving a dramatic look than a clever use of natural light. 

With the nearby mountains casting dramatic shadows over the valley, the living area features high roof windows that bring light to the room’s centre. The kitchen and dining areas face southwest and feature numerous roof and facade windows, all positioned to provide amazing views and maximum passive solar energy gain.

Because the home’s total window area is equivalent to some 51% of its net floor area, very little artificial light is needed during the day, and daylight levels are balanced throughout the home’s two storeys. Being the first carbon-neutral, single-family home in Austria, Sunlighthouse is equipped with a number of energy-saving technologies.

In March 2012, Sunlighthouse became home of the Dorfstetter family. The parents and two children enjoyed the numerous roof and facade windows, which provide stunning views as well as maximising passive solar heat gain and natural ventilation. 

Despite the house being oriented south-west, the Dorfstetter family has experienced no overheating due to solar gain. Automatic awning blinds and natural ventilation through the stack effect keep the building cool and pleasant.

While the Dorfstetter family tested the house's functions and comfort through their daily life, data of energy consumption and indoor climate were collected by VELUX Austria and VELUX Group’s partners at Danube University Krems and the Austrian Institute for Healthy and Ecological Building (IBO).

The monitoring proved the Sunlighthouse is a major green design success − its annual energy yield from solar cells, heat pumps, solar gain and other renewable sources exceeds its annual energy consumption.