Passive house sets a new precedent

Developers Simone Kreutzer and Tommy Wesslund have recently completed work on an eco-home in Sweden, clad in Kebony. Villa Circuitus, meaning ‘a going around’ in Latin, is a spacious, circular 175m² passive house containing four bedrooms, an open-plan kitchen and dining area.



he property’s round and compact body minimises heat loss, whilst providing a striking design both inside and out.

The Villa Circuitus was built to meet passive house requirements, with strict environmental demands in terms of design and construction materials. Both Simone Kreutzer and Tommy Wesslund are certified passive house experts with special expertise in energy and ventilation, knowledge they brought to the design of their latest project. They were the creative minds behind this project and cooperated with Nina Sandahl from SAJT Arkitektstudio to design the bespoke home, Sweden’s first circular passive house. All consultants involved with this build were also certified passive house experts; therefore the focus on sustainability was thorough, from the inception of the design all the way through to the final building process.

From Friday 13 to Sunday 15th November 2015, Villa Circuitus opened its doors during the ‘International 2015 Passive House Days’, with almost 700 Passive House buildings across 30 countries taking part to present the future of energy-efficient housing to the public. Thousands of participants around the world visited these buildings and received first-hand experience from both architects and passive house residents about the benefits of the highly energy-efficient Passive House Standard.

Construction took place between March 2015 and November 2015 with the owners moving into the property in December. The construction process has been thoroughly documented in its entirety, looking closely at the financial and technical elements, in addition to a range of soft skills required during construction. Since completion, the house has been closely monitored – this will continue for several years.

Preventing heat loss

The house has a 35m² veranda on the second storey, from which residents can view the beautiful landscape. Surrounding this veranda is a balustrade with integrated solar panels, which make the home self-sufficient for most of the year. The round shape has been carefully designed, partly to stand out in terms of aesthetics, but also to expose the smallest surface possible to the outdoor air and thus reduces heat loss. Large windows around the perimeter of the building allow lots of natural light to illuminate the property throughout the day and also help heat the building. Every window is custom-made to halve the loss of heat as compared to normal windows and the air circulating through the house is kept at a steady temperature by a two-stage heat exchanger which passes the air through a ground-based water heater then a post-heater. This two-stage process efficiently warms the air in winter to a temperature of 18.5°C – 20.5°C and cools it in summer so the air circulating is 16°C – 17°C.

All products and materials have been sourced to find the most sustainable and environmentally-friendly options, selected from: Sweden, Norway, Germany, Austria, Latvia, Denmark and Holland – each product was tested and approved. A passive house roof hatch, that opens using a remote control, was chosen to perfectly complement the distinctive nature of this property.

Alongside these high-tech elements is the widespread use of natural, environmentally-friendly construction materials. Recycled paper and glass are used throughout the structure and the whole house is built on a wooden frame with Kebony cladding. Kebony is a modified softwood that acts as a sustainable alternative to tropical hardwood. Developed in Norway, the Kebony technology is an environmentally- friendly, patented process, which enhances the properties of fast-growing sustainable softwood with a bio-based liquid.

By impregnating the wood with furfuryl alcohol, the wood’s cell wall is polymerised resulting in greatly improved durability and dimensional stability. Kebony therefore offers the performance qualities of a tropical hardwood, such as teak or mahogany, without the environmental damage.

Environmentally-friendly factors

Kebony’s environmental credentials have been proven by environmental consulting firm Bergfald & Co, which demonstrated that Kebony has a substantially lower carbon footprint than its tropical hardwood equivalents. The results of this study show that the carbon footprint for Brazilian Ipê is in the range of 7500 to 15,000 kilograms per m³, whilst the carbon footprint of modified Kebony is approximately 459 kilograms per m³. Both figures include treatment and transportation to Northern Europe.

The balancing of modern and natural elements can also be seen in the external aesthetic of the house which interweaves beautiful Kebony cladding with striking orange panels around the windows. The colour of Kebony wood mellows over time from a rich brown to an attractive silver grey patina, giving the whole structure a quiet, natural look, while the contrasting orange panels emulate the warmth and comfort emanating from the interior. The Kebony cladding helps the passive house to complement its natural surroundings, blending in with the rocky landscape, while also offering fantastic protection from the cold weather. In addition, Kebony’s durability and resistance to wear and weathering circumvents the need for expensive and environmentally-damaging chemical treatments, or indeed replacement.

One main aim for this build was to find a way to store solar energy; the designers have been working recently with a manufacturer to make this possible. As it stands, more solar energy is being produced than is currently consumed. If it is not possible to store the solar energy, there is a small expense each year for electricity. Although the cost is low, the developers were keen to receive a contribution for delivering additional solar electricity in the summer. In Germany, it is possible to sell additional solar energy back to the grid and purchase it back for half the price if required. Germany has made significant progress motivating its residents to produce renewable energy; however, this is not yet the case in Sweden.

Simone Kreutzer, Developer of Villa Circuitus, commented: “We have a passion for making sustainable homes and so we needed to ensure that every element of the house was responsibly sourced. The solar panelled balustrade, the recycled insulation and the striking Kebony cladding all help to realise our vision of a truly sustainable eco-home.” Per Thyberg, Country Manager Sweden at Kebony, said: “We at Kebony feel excited to be part of Simone and Tommy’s innovative design. Now the Villa is complete it looks stunning, has a fantastic open-plan layout and sets a new watermark for sustainability. We hope to be involved in many more projects of this quality in the future.”

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