Structural AnalysisMerz Kley und Partner
Building physics & construction ecologyIBO - Österreichisches Institut für Baubiologie und Bauököloge (Verein) und IBO GmbH
Technical support in building physics & energy conceptDonau-Universität Krems
Main contractor timber constructionKaspar Greber
Text description provided by the architects. The Velux Sunlighthouse in Pressbaum near Vienna is the first co²-neutral single-family-house in Austria. It was completed end of October 2010. The project was launched about two years ago by the Velux company as a part of their Pan European experiment, the so called “model home 2020” project. The goal is to develop, build and analyze six different houses in five European countries, each following its own approach to progressive and sustainable building and living.
The challenge of the Austrian model home was to create a house that taps the full potential of the plot (like the wonderful views, exposure to the sunlight, maximum of privacy between the existing houses, …) on one hand and to develop an energy and ecology concept to erase the ecological footprint of the house within the next thirty years on the other hand. What distinguishes this project from many ambitious preceding projects is the need and wish to combine minimized numerical values for energy efficiency with ambitious architecture.
Fortunately the clients had chosen an anything but ideal plot for the Austrian model home. It is a slender and long piece of land that declines towards a beautiful (but shading) wood with high trees in the Southeast. The plot is flanked by a dense hedge in the Northeast and a high wall in the Southwest. The two close situated neighboring houses on both sides leave just a little scope for privacy in between. The wonderful view to the lake which is situated in the valley in the East can only be caught by getting a step deeper into the ground. In short: A design concept that uses a maximum of the potential that the plot offers had to be more than a lip service, if the ambitious targets were supposed to be accomplished. This makes the results of the project even more precious as affordable plots in a mountainous country like Austria rarely offer ideal conditions.
The energy concept of the building was developed in collaboration with the Danube University of Krems. The building equipment includes a high performing heat pump, 48 m² mono crystalline photovoltaic roof panels, 9 m² thermal solar panels for hot water and a controlled air system with heat recovery. The heat insulation of the shell surface of the house is optimized and the windows fulfill passive house requirements. A (in Austria) so far disregarded demand was to obtain a maximum of daylight to lower the energy consume for artificial light. The reached daylight factor in every single room is on average five times higher than the usual standard. The roof and facade windows were strategically positioned to provide stunning views, to maximize passive solar energy, to enable an optimal, natural ventilation during summer time and to minimize the thermal losses during winter time. In fact the Sunlighthouse’s total window area is equal to 42% of its floor area. Like the outside planking, the interior fitting is made of spruce wood. To keep the wooden surface bright and avoid darkening, it was treated with white pigmented natural oil.
All materials had to be evaluated by their ecological qualities before they were authorized to use. The Austrian Institute for Construction Biology and Ecology (IBO) also benchmarked the co² valuation of every assembled material. Using locally grown and processed wood as main material to optimize the co² values are self-explanatory, but as the building is positioned in a hill it was also necessary to use concrete for all the grounding construction elements. Instead of ordinary Portland cement (which shows a quite poor co² balance) blast-furmace-slag, a spin-off product from steel production with extremely low co² output, was used to mix the concrete. The applied insulation material is sheep wool and recycled cellulose.
In the end the goal was accomplished. The Sunlighthouse will produce more energy than the building and using of the house consumes, which makes it a small “power station” and a beacon project for further conscious and sustainable planning and building.