The 2,000 sq ft (186 sq m) Solar Barn Loft uses overhangs and openings on the southern façade to minimize solar heat gain in the summer and maximize it during the winter. Deciduous trees block the summer sun, but allow winter light through. A large patio bounces light upward towards the underside of the south-facing eve, which itself is reflective and helps to light the house naturally. Heat, meanwhile, is not reflected.
The roof uses an inverted scissor truss upon which a 48-panel photovoltaic array is installed. According to Lukez, the array would (conservatively) generate around 16,300 kWh of electricity per year. The building, he estimates, would use only around 14,905 kWh per year, leaving a healthy surplus.
The angle of the inverted scissor truss roof is optimized for exposure of the solar panels to sunlight and also to allow air to flow up through the house. Spaces inside the truss can be closed off when it is cold and can be opened up for natural ventilation when it is warm. There are also air ducts to bring cold air in through the basement of the house that can be opened and closed as required.
The design employs "super-insulated walls" with a double wall cavity that is filled with blown cellulose. Icynene spray-in-place soft foam insulation is used in the roof, which is 100 percent water-blown and, as such, does not contain environmentally harmful blowing agents. In addition, the design features triple-glazed windows and 4 inches of rigid insulation below the basement floor slab, all of which should add up to very high levels of thermal insulation.
A 12-in (305-mm) thick concrete slab provides thermal mass for the southern half of the ground floor. The slab is heated up by the sun during the day to warm the house at night. On warm night, windows can be opened to keep the house cool.
Elsewhere, flooring and siding in the house is made from wood and recycled materials and the driveway and other paved surfaces are semi-porous. Roof water is collected for use in toilet cisterns.
The Solar Barn Loft project was designed as part of a competition sponsored by the US town of Northampton, Massachusetts. Lukez explains that the town provides land to prospective home owners at nominal cost if they use one of the winning zero-energy designs.
Although construction of a Solar Barn Loft has yet to begin, Lukez says there have been a number of inquiries and that he expects to secure a build within a year. Construction would take around another 12 months at a cost of between US$500,000 and $600,000.
Solar engineering and calculations by Derek Brain of Transformations Inc.Source:
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