This is the renovation that defied expectations. The dilapidated timber cottage was relocated onto this large rural property many years ago with little regard to orientation and the demanding extremes of climate in this inland region.

Subsequently left to slowly decay, it was debatable whether it had a future at all. But thanks to a client committed to showcasing how deep a deep energy retrofit could go, it is now comfortable, healthy and very energy efficient.

The new extension is unashamedly modern and creates a bold contrast from the exterior, differentiated by its roof form, cladding and colour. Its timber cladding is echoed by the generous walkways and decking surrounding the cottage, constructed from Australian hardwood timber.Inside, period features are retained in the original bedrooms, with their internal curved wall and feature plaster ceiling. The kitchen is modern and practical, opening to an open-plan dining and living room.

Everyone is happy that a beautiful pear tree shading the north-facing window could be kept. Enough sun filters through its bare branches in winter to provide needed solar gain.

The cottage had to be stripped back to its bones, a sturdy timber frame that was still fairly straight. Design took the deep retrofit seriously. First an air control layer was established, followed by insulation: batts between studs plus a continuous layer of woodfibre insulation board. This was followed by a weather tight layer and finally new cladding.

The climate (both hot and cold) required an air tight solution for thermal control which also necessitates reliable ventilation with mechanical heat recovery with ventilation (MVHR). All of these elements contribute to the Passivhaus strategy that delivers energy efficiency alongside a healthy and comfortable indoor environment.

The project is targeting Passivhaus EnerPHit certification and the final stage of certification is almost complete.

David Smyth