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Romsey Road
Carbon-negative replacement dwelling in Winchester

The original brief for this project was to extend a 168m² 1930s/40s detached house that the clients had recently bought for their young family. Initial feasibility studies demonstrated that extending the existing property would not deliver the either the layout or energy performance that the clients were seeking to achieve (and could cost close to what a replacement dwelling would cost given that extensions attract VAT whereas newbuilds do not).

The key requirement for the revised brief for a five-bedroomed replacement lifetime home was for it to be low maintenance and highly energy efficient / low carbon. The house is constructed in brick, with a clay roof tile and a zinc-clad rear dormer – all low-maintenance, high-quality materials. The main body of the house has a simple gable-to-gable form which is both efficient to construct and creates a large, south-east-facing roof in which has been installed a 7.4kWp photovoltaic array with integrated rooflights serving the two “in-roof” bedrooms. The roof also has two larger, central rooflights which flood the three-storey stair atrium with light and can be remotely opened if required to provide stack ventilation cooling on warm days. Large windows throughout the rest of the house and an eight-metre-wide sliding door to the kitchen / dining / living means the house enjoys very high daylight factors and natural ventilation as required.

The combination of a ‘fabric first’ approach to the construction of the building envelope (very highly insulated floor, walls & roof, low u-value windows, low air permeability) combined with the on-site renewables (solar panels, ground source heat pump interfacing with battery storage) means that the house generates more energy than it consumes and is operationally carbon-negative (-0.34 tonnes per year) with an A-rated EPC of 97. For comparison: the average UK house is responsible for generating 6-8 tonnes of carbon per year.

Structural Engineer: AWA Consulting Engineers

Energy Assessor: Darren Evans Associates

Building Control: Assent Building Control

Principal Designer (CDM): Ralph Kent / architect

Main Contractor: Harpoint Builders

Demolition: Wessex Demolition & Salvage

Boreholes: Geocore

Structural steelwork: Conja

Brick: Wienerberger Marziale

Roof tiles: Dreadnought Tiles

Zinc dormer supply: Anthrazinc by VM Zinc

Zinc dormer installation: Pace Roofing