international Larixhaus, Catalonia Words: Oliver Style The Larixhaus is the first pre-fabricated straw bale passive house built on the Iberian Peninsula. This single family home is located in the town of Collsuspina, near Barcelona. Developed by Jordi and Itziar in 2013, a pioneering young couple who wanted a comfortable, healthy and low-energy home built from natural and renewable materials, the Larixhaus brings together a team of passive house professionals who delivered it in five months, insulating it with locally sourced straw bales. The Larixhaus joins a short but growing list of passive house constructions in Spain, where climate-responsive passive design is well suited to the wide varieties of weather conditions, which range from cold and temperate to hot and humid. The dwelling is small and compact, with an optimised passive design and impressive level of airtightness — it achieved 0.32 air changes per hour on the first blower door test. Windows have timber frames with argon-filled, low-e tripleglazing. The airtight layer is provided by 22m OSB, with timber breather-board behind ventilated larch cladding on the outer skin providing an exit route for any moisture in the building assembly. Summer comfort is achieved through the careful choice and orientation of opening areas and external blinds on the southern façade. The timber superstructure and external cladding is PEFC certified. Healthy indoor air quality is achieved by using non-toxic natural materials together with heat recovery ventilation. The building’s embodied energy and fabric CO2 emissions are minimised by prioritising the use of natural, non-toxic, renewable building materials (certified timber, locally sourced straw, and cork). The pre-fabricated construction system developed by the contractor, Farhaus, allows for rapid on-site assembly, pre-installation of the airtight layer and window frames, with associated cost savings and near-zero onsite waste. Future installation of a grid-tied photovoltaic array will bring the building to a net-zero energy balance, with a rainwater catchment system to minimise mains water use. The Larixhaus puts high-quality straw bale passive house construction firmly on the map, coming in with a final build cost of €1,270 per sqm.
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