A net-zero house project called SunBloc has won the 2012 RIBA President Medals Student Awards, a prestigious architectural competition that takes place annually in the UK. Devised by students from the London Metropolitan University, SunBloc is tailored for the Solar Decathlon Competition, but the students say it can be adapted to other contexts.
The building employs a composite construction system comprised mainly of expanded polystyrene (EPS) foam blocks and steel cables. The materials are fairly inexpensive and the house does not require skilled workers to assemble it – a small group of people can get the job done.
In order to make the blocks, which were developed in conjunction with structural engineering firm AKT, the students used a handheld hotwire foam cutter and laser cut templates, which also serve as joints between blocks for air tightness. After positioning, the whole structure is post-tensioned, a process whereby a wall is "squeezed" using threaded steel rods. The SunBloc team says the EPS foam blocks can be easily put on a lift by two people, as the material weighs less than 100 kg (220 lbs) per square meter (10.7 square feet).
Due to the material's lightness, inertia against temperature fluctuations (technically known as thermal mass) is provided by an internal finish of clay with embedded phase change wax granules – these store heat when the ambient temperature is high, then release it when the temperature drops. Corner windows and high-level openings let in adequate daylight, plus the solar exposure could be maximized with a south-facing porch. An acrylic-based coating is used to treat the exterior.
Besides the solar photovoltaic panels that cover the roof, there are also plans to boost the project’s sustainability in terms of building materials as well, replacing EPS as the main component with BioFoam produced from industrial waste streams. The facade can also become a living wall.