Why do people have walls, for heaven’s sake?” says Mary Morris as we stand in the light-saturated hallway of Blackwood, her bespoke energy-efficient home in Barbury, Wiltshire. Commissioned by Morris and her partner Klaus Failenschmid, Blackwood does have a few solid walls but, wherever possible, stretches of glass let natural light flood in, as well as passive solar gain (heat) and an immeasurable sense of space.

In fact, Blackwood is all about borrowed light. Why flic k a switch when you can get it for free? This is not only ecologically sound but, as Failenschmid puts it: “It is more in tune with how your rhythms should work.” Light when it’s light, and dark when it’s dark. “We don’t like to use electric lights when we can borrow from daylight,” he says. At dawn, ambient light illuminates his way downstairs and into the kitchen to put the coffee on.

Where we work, there are windows on three sides and a view into the distance. What more could you want?

Morris and Failenschmid, who both work in IT, love art, design and contemporary, sustainable architecture. They spent 10 years looking for a plot that ticked enough boxes for them to go ahead and build their ideal home. Privacy, views, land to grow fruit and veg and a railway station within walking distance were all on the list. The station requirement had to go. What started out as a search close to London, where the couple first lived together, kept shifting further afield, due to the high price of land. They never planned on moving so far west, but affordable plots “are almost impossible to find,” according to Morris, who grew up in New Zealand. “There’s no point building your ideal house on some handkerchief of land in someone’s back garden.”

Back to the land: the ramp to a wildflower meadow, and vegetable plots outside the house. Photograph: Neil Speakman/Maple Photo

The couple are fans of Huf Haus – the German company that makes prefab homes of glass and wood – and the bedroom in their previous home had a glazed wall overlooking their garden. There was never any question that their new, built-from-scratch home would also feature vast expanses of south-facing glass, and be built according to Passivhaus design principles of minimal energy consumption for heating and cooling. Solar panels provide electricity and hot water, there’s a heat-recovery unit and airtight triple glazing stops energy seeping out. The west wing roof slopes down towards the south, for the solar panels to absorb light, and the east wing roof is angled up towards the south, to allow light and solar heat to bathe the living room. There are fruit trees, a greenhouse, vegetable beds and a herb garden. Apart from wanting an energy-efficient, life-time home, Morris and Failenschmid asked architect Helen Seymour-Smith to include one big wall for their growing art collection, plus direct access to the garden.

The end result is a striking design packed with harmonious contrasts: a modern house in ancient rural surrounds with England’s oldest road running down one side. There are also semi-industrial features, such as exposed pipes and large metal hinges wrapped in warm spruce; a building that’s black on the outside, but unbelievably light indoors. Elongated bricks outside give weight to the east wing, but a lighter, corrugated iron encasing the west wing is what visitors first see when they arrive.

Downstairs everything leans towards the cosy and domestic, with a symmetrical, matt black Bulthaup kitchen, walk-in pantry filled with homemade jam and a central “dining hall” featuring a fishing rod-style aluminium creation made by Failenschmid that dangles three diminutive spot lights over the table to give a “homely, focused” light. The main guest bedroom is the only room with curtains – guests struggle with glass walls – and the TV den-cum-second guest bedroom is home to a favourite piece of furniture left over from the couple’s Arts and Crafts phase: a dark oak cabinet from Austria, thought to be the work of the architect Adolf Loos. These days they’re hooked on mid-60s furniture, mainly by designer Richard Young and Merrow Associates, who worked with chrome and rosewood, such as Young’s rosewood, modernist sideboard in the dining hall and the chrome dining chairs with black leather seating.

Modern lovers: design fans Klaus Failenschmid and Mary Morris in their newly built house. Photograph: Emli Bendixen

Upstairs, via a metal staircase inspired by the classic New York fire escape, the house opens out into an airy loft. The entire roof structure is free of internal supports, with clerestory glazing (a ribbon of windows between roof and walls) to make the roof itself look as if it’s floating. Their living room and bedroom sit on one side, and a large his-and-her’s office on the other, with adjoining desks and window seats to watch visitors arrive and look out over their wild garden while they work.

“The idea was that when we’re working, we’re not hidden away,” says Failenschmid. “There are windows on three sides and a view into the distance. What more could you want?”

Living in a wooden house is supposed to be good for you

From their desks, they can also look over to the living room and the side of their “pod”, which rises up from behind the sofa. The wooden pod is effectively a room within the wider room – living room to the front and bedroom to the back – that houses a walk-in closet and a pale grey shower room. “We always wanted a pod,” says Morris. “It’s almost like a piece of furniture that sits in the open space.” But it came with a battle, as their builder wasn’t happy with the idea of a glass ceiling (now synthetic), which Morris and Failenschmid were set on for the pod’s shower room, to give a feeling of height and to steal light from the clerestory. “We had to convince everyone we wanted a see-through ceiling for all that borrowed light,” Klaus explains.

The only way is up: a metal staircase leads from the open-plan kitchen to the loft. Photograph: Emli Bendixen

As for the house’s bare, wooden walls, Failenschmid grew up with wooden houses in Germany (Passivhaus is also a German concept), and they were both drawn to the idea of panelling, until they settled on cross-laminated timber – steely strong, with no decorating required: “It’s plywood on steroids,” says Morris. And they love the “honest” effect.

“Living in a wooden house is supposed to be good for you,” says Failenschmid. “I certainly find it calming to live here.”

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