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A gentrified farm house, a groundbreaking Passivhaus built in a London garden​ and a handcrafted concrete chill out house which has been 10 years in the making are among the latest projects featured on Channel 4's special four-part TV series House of the Year.

The Grand Designs special sees presenter Kevin McCloud, architect Damion Burrows and design expert Michelle Ogundehin visit 20 projects across the UK that have been longlisted for the Royal Institute of British Architecture's annual award for architectural excellence.

This week's episode introduces five ingenious “down-to-earth” homes that have used pioneering building materials and techniques. These homes could be blueprints for sustainable homes of the future.

Two of the projects featured in the third instalment of the programme will join the House of the Year finalists revealed so far, ahead of the winner being announced next week.

The five contenders

1. Max Fordham House, London

By Bere Architects

Max Fordham House is a groundbreaking three-bedroom electric house in Camden

This all-electric house was squeezed into the tiny city garden of renowned physicist and engineer Max Fordham in Camden Town, north-west London.

The new-build, zero-carbon home which generates its own heating is now one of the most advanced high-performance houses in the UK.

The three-bedroom property is passively solar heated during the day, while the thermally massive structure and the shutters help retain this heat throughout the night.

An airtight, thermal envelope wraps the building’s structure to completely insulate it, while a heat pump and bespoke insulated window shutters replace the need for external heating systems in winter.

In summer, the staircase draws air up through the building and the windows open fully to reject the heat, while cool air is supplied through 3D-printed jet nozzles.

2. Secular Retreat

by Atelier Peter Zumthor with Mole Architects

Secular House took a team of local craftsmen 10 years to build using a hand-rammed concrete technique

Living Architecture invited one of the greatest architects in the world, Peter Zumthor, to create Secular Retreat in South Devon.

Set on a remote hilltop, this unusual holiday retreat is mostly concealed in the landscape, surrounded by leaning pine trees.

A team of local craftsmen took 10 years to complete Secular Retreat, mostly because it was built using a hand-rammed concrete mix which needs to be poured in layers, a technique which gives stripes to the walls and foundations, both inside and out.

The entrance of the home is beneath the massive overhang of a dramatic cantilevered white concrete roof. Various timbers used inside “bring the landscape in”, such as pearwood flooring in the bedrooms, while underfloor heating and the thermal mass of concrete walls and columns create an insulated, cosy living space from which to enjoy looking out on a 360-degree open landscape.

The magnificent views are best enjoyed from bespoke armchairs perfectly positioned to allow their occupants to become transfixed by the procession of clouds across the South Devon landscape, and watch the sun set over the valley below.

3. Hill House Passivhaus, South Downs

By Meloy Architects

Hill House Passivhaus in the South Downs was built on the footprint of two run-down old chicken sheds

The architect's brief for this contemporary eco-house was to build a home on a remote, rural plot in the South Downs for his own family, while achieving Passivhaus certification on a small budget.

The single-storey, low-energy home was built into the crown of a hill, offering great views across the landscape and surrounded by a screen of large, mature trees. It replaced two dilapidated sheds formerly on the site, with a compact bedroom wing set at a right angle and separate open-plan living spaces showcasing the views with floor-to-ceiling windows and skylights.

The house requires little additional energy for heating. Hot water is generated with an air source heat pump and additional space heating can be provided through a sealed wood-burning stove. Internally a thermally separated polished concrete floor also acts as a heat sink to even out fluctuations in temperature.

4. Hannington Farm, Northamptonshire

By James Gorst Architects​

Hannington Farm is a gentrified farm house with a wing purposefully designed to house an indoor pool, gym and wine cellar

This countryside home clad in honey-coloured Cotswold stone is mostly hidden from the outside, concealing much of its contemporary layout and cavernous living spaces.

This new-build, family house on a deer farm in Northamptonshire blends traditional farmhouse or barn conversion design with the features of a modern manor house.

A series of asymmetrical pitched roofs rising from the building's central “knot” structure allows for separate wings which also split the rooms by two thirds to one, creating flexible, triple-height living and entertaining spaces.

Exposed timber beams throughout have been lime-washed to a contemporary pale blonde, while floor-to-ceiling windows flood the angular rooms with light.

5. House Lessans, County Down

By McGonigle McGrath

House Lessans is an L-shaped building of perfectly pitched zinc roofs over cool concrete blockwork

The rolling landscape of County Down provides the setting for this carefully orchestrated conversion built on a tight budget.

An existing barn and shed with double yard were the remnants of a small farmstead on the site. A new forecourt, a discrete bedroom block with private courtyard and living spaces were added to the converted original structure, all painstakingly designed to look over the picturesque countryside.

The new buildings deliberately mirror the materials used for local corrugated agricultural outbuildings, with simple pitched roofs of zinc on masonry walls creating courtyard spaces.

Inside, cavernous living spaces reflect the proportions of the original barn.

The winner of RIBA House of the Year 2019 will be announced on Channel 4's Grand Designs: House of the Year on Wednesday, November 13.