garden view of house at night with lights on

Mill Race

A low energy home in Wiltshire
Location Donhead St Mary, Wiltshire
Status Built
Use Residential
Client Private

This large family home with guest accommodation, home office and workshop is located in the village of Donhead St Mary, in Wiltshire. The design had to be sympathetic to its rural location and its neighbours within the hamlet, plus the potential impact on the setting of the neighbouring Listed water mill and mill house.

entrance approach to house with large black barn and pebble drive
beautiful dining room extension with large glass windows
side elevation of stone house with extension taken from across river

A traditional house with contemporary features

The main body of the house, a building of traditional appearance and faced in Shaftesbury Greensand stone, is set at 90 degrees to the road to present as small an elevation as possible to the street scene and minimise its size when viewed from the lane.

The T shaped plan maximises sun, and views from the open plan living spaces, over the stream at the bottom of the site.

The subservient guest accommodation with garage and workshop under is set back from the main house and is finished in a dark timber cladding to reduce its effect on neighbours. To the rear, a Juliette balcony allows the first floor door to be fully openable.

entrance to house behind black gate at dusk with lights on
building a beco wall form on site

Modern building methods

The house is constructed from Insulated Concrete Formwork (ICF).  The BecoWallForm system is so energy efficient that additional input required from the air source heat pump is minimal.

The construction process is quick, tidy and precise. It consists of large hollow polystyrene blocks, components that lock together without intermediate bedding materials, to provide a cavity into which concrete is poured. Once set, the concrete becomes a high strength structure and the form-work remains in place as permanent thermal insulation. The wall is so strong that major beams can be placed directly onto the wall without padstones. It was so easy to construct that it was built by just two people.

interior large open-plan kitchen diner with blue kitchen island

Low energy living

The underfloor heating input temperature can be set to the remarkably low figure of 25 degrees (providing a comfortable room temperature of 18-20 degrees) due to the success of the highly insulated walls and air source heat pump.


Main Contractor Hersnmine Developments Ltd
Structural Engineer Harvey & Snowdon
Walls Beco ICF & Shaftesbury green stone
Glazing ODC glass

Size 445.2 sqm
Cost £960,000
Completion Date 2023
Photography Jack Lodge Photography


timber stair detail with dark blue walls and large indoor plant taken from kitchen
rear view of house with stone and timber cladding and Juliette balcony