Klein Kastanjes is situated in a unique position in the old winemaking suburbs of Cape Town – sandwiched between two wine farms with backdrops of the Steenberg Mountains to the west and False Bay to the East. The Clients brief was to upgrade the existing poorly thatched house to be energy and resource efficient, with minimal increase to the existing bulk and footprint but with a radical new look and reconfiguration of space internally. The recycling of character timber elements, such as doors and sashes with stained glass from the old house was another strong part of the Clients brief, which was challenging when placing them in new facades together with large modern openings and aluminium sliding doors.

To achieve the former, long span precast slabs were used for the upper storey which allowed for the complete opening up of the ground floor plan and the new slate roofline was raised by 1m to create a series of attic story bedrooms and high volumes. Keeping to the original house footprint limited the overall increase in floor area to only 12m². A glazed bridge linking the main house to its adjacent outbuilding increased the house’s overall functionality significantly by joining the two buildings and creating new spaces. Aside from providing access to the main studio and guest suite – the bridge itself becomes a new study lounge and doubles as a porte-cochere to shelter the main entrance below.

To achieve the latter, the older original parts of the house were clad in karoo stone, and roofed with new thin slate. Contrasting this – the new box dormers were flush clad in zinc, to express them as bold projecting frames that stem from the ground level and serve to order the facade and separate finishes. As strong ordering elements they contain openings on both levels with balconies that slide out between the frames. Rainwater guttering and other vertical services are concealed within the zinc box frames to keep all external finishes free of unsightly piping.

The contrast of the framed zinc dormer elements against the blue black slate roof and stone cladding creates some drama and helps to articulate the new and old alongside. This reinforces the narrative for the buildings reincarnation – an eclectic mix of new metal clad dormers with contemporary louver screened openings that push out through the older slate and stone clad parts of the building. The recycled teak stained glass sash windows are then more comfortably located within the deep stone reveals of the older parts of the building. Extensive recycling of old timber into new trusses and of all salvageable fittings carries the spirit of the old house through into the new.

The house responds to all seasons with terraces on the North, West and South sides with the main entrance from the East. Dappled north light filters in through the koi pond to a cellar beneath the TV room with subterranean views of the lazy fish. A water course from this pond circulates around the house via small planted channels to smaller ponds at each terrace before filtering through a reed bed filter into the natural pool. Overlooking the pool on the upper garden terrace is a double volume stone clad pool pavilion. The tennis court finishes off the lower garden terrace.

The house is fully automated and energy efficient in line with Passivhaus aspirations. Floors, walls and roof are well insulated, new windows and doors are double glazed while existing sashes are re-glazed with low E glass. In summer evaporative cooling is brought in through the roof at high levels to drop down through the double volumes into the living areas. In winter – primary warming is driven by the two large fireplaces situated in the double volumes and a hydronic underfloor heating system. Warm air rising into the volumes is drawn through fans into the bedrooms. Here it is exhausted via a heat recovery ventilation system and warmed fresh air is ducted back down to the lower levels ensuring fresh air exchange with minimal heat loss. A scalable solar photovoltaic system now generates around two thirds of the electricity consumption for immediate use within the house with battery storage for back up power.

Rain water is harvested for irrigation and grey water is recycled back to the house for flushing WC’s and for washing laundry. An insulated hot water ring main feeds bathrooms and hydronic towel rails, ensuring hot water on demand and eliminating cold water wastage. The Hydronic under floor heating is fed by a hybrid solar thermal & heat pump combination. Heat exchangers transfer required heat into the floor in winter and discharge excess heat into the swimming pool in summer. In addition, the two large fireplaces are fitted with custom made stainless steel hot water manifolds which at high temperatures circulate hot water to the heat exchangers to boost their efficiency.

The project has served us as a case study for the application of an integrated approach to designing and solution finding from the Client and the professional team. It has lead to the deployment of a range of elegant and sophisticated energy efficient solutions and is a model of innovation in the combination of these systems with each other and in synergy with passive design principles.