Gaia Architects were commissioned to design a dwelling on a site overlooking the River Tweed in the Scottish Borders. Plummerswood Active House is designed on ecological design principles to create a healthy, comfortable, energy efficient home. This relied on implementing basic, but fundamental, environmental strategies.
It is the first house to be constructed in the UK to the internationally-recognisedPassivhaus Standard using the glue-less mass timber Brettstapel technique. It follows from an initiative by Gaia in 2002 to promote UK manufacture of Brettstapel, which saw the construction and completion of the Acharacle School in 2007. In both cases the superstructure was prefabricated in Austria and shipped to the site.
It was constructed to asix week timetable, in the midst of the winter of 2010, on foundations built by local builders. The fit out was by a local builder and the fixed furnishings are a designcollaboration between Gaia and Real Wood Studios. It was completed in Autumn 2011. Plummerswood Active House won the Scottish Homes Award for Architectural Excellence in 2012.
Positioned on an east-facing slope and looking south over the Tweed Valley, the house was designed through extensive dialogue with the clients, resulting in a simple, L-shaped layout across two storeys, with the intersection forming the double-height entrance. See :The clients story
Passive techniques such as orientation for daylight and solar gain with external blinds, super insulation, thermal mass, moisture mass and air-tightness (0.6 m3/hr/m2 @ 50Pa (0.46 ac/h-1) have been utilised. Areas of the house that will be subjected to high levels of indoors moisture, e.g. bathrooms, kitchen and wet room, have clay board and clay plaster applied to the ceilings. This material is very hygroscopic and therefore extremely efficient at helping to maintain comfortable humidity levels in the house.
A wood burning stove comprises the supplementary heating. The results of the early DomEARM indicate that Plummerswood uses less energy than a dwelling designed to achieve a Level 6 in the Code for Sustainable Home development ratings but as it doesn’t produce electricity to offset this the overall CO2 production is around Level 5. The lack of performance of the solar thermal panels due to poor installation, which is yet to be resolved, has been a source of frustration.
Special attention was paid to the avoidance of synthetic and heavily processed materials and those with polluting impacts on indoor climate and waste streams. The insulation is made from low-grade wood fibres bonded by tree resin. It is vapour-permeable, which means that it allows any excess moisture in the structure to pass through it without affecting how well it insulates.
The current extensive monitoring will appraise whether the building form was optimised in terms of orientation, assess the contribution of thermal and moisture mass, and examine the relationship in energy terms between client controlled natural ventilation and MVHR. The occupants are keeping a diary to assist in the analysis.