Case
Energy efficiency in buildings
Smart cities
For more than 80 years, the VELUX Group has created better indoor environments by bringing daylight and fresh air into homes and other buildings all over the world. The VELUX Group was founded in Denmark and is today an international company with a presence in 37 countries.
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Credit: Adam Mørk & Michael Winkelmann
Creating a carbon-neutral home that optimises energy efficiency while maintaining a high standard of indoor climate and comfort poses a significant challenge—especially when integrating maximum daylight exposure into the design. In Austria, this challenge was intensified by the Sunlighthouse’s location: a steep, partially shaded slope facing southeast towards the Vienna Woods. The objective was to balance energy efficiency with daylight architecture while ensuring a surplus of renewable energy generation.
VELUX, in collaboration with HEIN-TROY Architekten, developed the Sunlighthouse as part of the Model Home 2020 project. Designed to maximise daylight and passive solar gain, the house features a high proportion of strategically placed roof and façade windows—amounting to 36% of the net floor area. This ensures an average daylight factor of at least 5% in all living spaces, reducing the need for artificial lighting and creating a healthy indoor environment.
To maintain an optimal indoor climate, the home employs a hybrid ventilation system. In spring, summer, and autumn, natural ventilation is facilitated through automated window control, while in winter, a mechanical ventilation system with heat recovery ensures fresh air circulation without excessive heat loss. Overheating during warm months is mitigated through stack-effect ventilation, night cooling, and awning blinds.
The Sunlighthouse is powered entirely by renewable energy. It integrates:
The combination of these technologies allows the house to generate more energy than it consumes, making it a positive-energy building. Over a 30-year period, it will have produced enough clean energy to offset the emissions generated during its construction.
The prime objective of Sunlighthouse was to reduce overall energy consumption (parti cu larly primary energy) to a minimum without sacrificing living comfort.
Since its completion in 2010, the Sunlighthouse has demonstrated the feasibility of carbon-neutral living without compromising comfort. Yasmin and Ludwig Dorfstetter, who moved in with their two children in 2012, experienced a comfortable indoor climate with ample natural light and stable temperatures year-round. Despite its orientation, the house did not suffer from overheating.
The project was closely monitored by VELUX Austria in collaboration with Danube University Krems and the Austrian Institute for Healthy and Ecological Building (IBO). Their research confirmed the home’s positive energy balance, with an annual surplus of 12.2 kWh/m².
The Sunlighthouse has received several awards, including the Austrian National Award for Environment & Energy Technology in 2010, recognising its innovative approach to sustainable housing. The project serves as a model for integrating energy efficiency, indoor climate, and resource-conscious construction into future home design.
“Sustainable management of natural resources has been a big part of our professional lives for a long time. So we’re excited that this experiment also gives us an opportunity to help shape the future of ecological home-building and living in our private lives.” Ludwig Dorfstetter
Built in 2010 not far from Vienna, the Sunlighthouse was Austria’s first carbon-neutral single-family home.
Nine up-and-coming Austrian architects pitched their ideas for carbon-neutral home designs that kept energy consumption to a minimum without sacrificing the residents’ comfort or standard of living. Maximum daylight and solar energy were key parameters, as was an architectural profile suited to the unique landscape.
Read more about Sunlighthouse
