Stephen Coates has completed an ecologically responsible domestic refurbishment and extension project in Kingston Upon Thames


Stephen Coates Architects

Architect Stephen Coates has sensitively reworked an Edwardian villa and added a Passivhaus standard annex on a suburban plot in Kingston Upon Thames. Located within a conservation area close to the town centre, the existing double-fronted house included poorly constructed extensions to the rear, but provided the width, high ceilings and potential to extend and create a large living space overlooking the west-facing rear garden. The plot also contained a bungalow dating from the 1970s. An early decision was made to demolish the poorly constructed building and replace it with an energy-efficient annex containing guest accommodation.


The villa was stripped back to the brickwork, joists and studwork, with only the stair in the centre of the plan remaining. All windows have been replaced with double-glazed, timber-framed, sash and case units. Insulation has been added to floors, ceilings and roof. New services include air conditioning with an air source heat pump and inverter technology.

Site plan; ground and first-floor plans; section

The villa extension incorporates two planes of yellow stocks in a Flemish bond to match the existing building, and what appears to be a slender concrete slab evoking of the lintels on the front façade. An ‘up and over’ slot window separates the new and old structures. Full-width sliding glass panels connect the living space to the garden. A sedum roof provides some additional insulation and ‘softens’ the view from the first-floor windows.


The annex is constructed from structurally insulated panels, which were erected in a week and then waterproofed and clad in fire treated and black-stained Siberian larch. Triple-glazed windows combined with high levels of insulation and airtightness ensure low-energy in use. A solar photovoltaic system installed on the south-facing roof is projected to supply 4.8 kWp power, which is 100 per cent of the house’s projected needs during daylight hours. Smart home technology links the two buildings and enables remote control of audio-visual equipment, lighting, curtains, and the security system.

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