Breathe easier: Grand Designs' 'healthy house' built for kids with life-threatening allergies proves an inspiring wake-up call

Grand Designs is no stranger to ambitious — sometimes even reckless — self-build projects, but there's a serious motive behind this week's aspirational project, which also happens to be our favourite yet.

London couple Elinor, 37, an art dealer by day and husband Born, 36, a sports technology entrepreneur, have two young sons who both suffer from an agonising range of life-threatening allergies, from dust and pollen to chemicals in certain cleaning products, forcing them to spend a lot of time in hospital.

Unable to move out of London due to job commitments, these inspiring self-builders plan to channel their savings into building a "hypo-allergenic home" in Richmond where their sons Avery, seven, and Pascal, five — and their three-year old daughter Blakely-Rae — can grow up literally breathing easy.

But sourcing low-toxin materials and installing a mechanical ventilation system to filter the air will cost money, and ideally they'd like their new family residence to reflect their personalities, too. Elinor owns a gallery and is bubbling with ideas for how to bring the place alive, providing they have any pennies left in the pot come move-in day.

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IT’S GOING TO BE A SQUEEZE

Presenter Kevin McCloud meets the couple as they face their first dilemma: how to ensure lorries and cranes can access the quarter-acre plot in Richmond they've just bought for £765,000, when it's tucked down a narrow driveway.

They've been granted permission to use the neighbouring field, but the owner is selling up, and they have just six months until they're no longer able to drive through it…

"It's an incontrovertible fact, isn't it? No matter how fine and noble your project is, if you can’t get to the site, you can't build it," says Kevin, cutting straight to the point.

"OUR BEAUTIFUL BACK GARDEN SHED!"

Born and Elinor have enlisted the help of a team of 'healthy building specialists', who are adapting their original architect’s design to meet their bespoke needs.

Because theirs is a garden plot, the council has limited them to "a single-storey house with basement dwelling".

The four bedrooms will be housed in a large concrete basement overlooking a sunken garden, while above ground, huge, pre-formed, pre-insulated timber panels from Latvia will give the appearance of "a beautiful back garden shed".

Clad in larch and white render with a modest, grey zinc roof, the entire building will be skimmed with an airtight membrane before being fitted with the aforementioned mechanical ventilation system, which costs £10,000.

"We want to make a haven for our kids to grow and thrive in," says Born, whose budget is limited to half a million pounds, which is tight for a project with such high-spec demands.

GETTING HIGH-TECH

Luckily, the basement is excavated in record time, and the final big delivery dramatically arrives with just nine days to go until their access is cut off.

The panels slot together rapidly, "like a massive Ikea flatpack". Then, an enormous fan is used to depressurise the home so the team can check for any air leaks. They light a match and hover it around each seal - if the smoke moves, they know air is getting in. Once they're happy, the metres of white piping that will carry the filtered air are fixed throughout every room.

Next, the couple call in a lighting designer with expertise in using 'biodynamic lighting' to mimic natural light in dark living spaces. He will install this smart lighting, which costs a further £4,000 but helps to regulate our sleeping patterns, furthering the positive health impact of this special home.

FEELING FORTUNATE

Midway through the build, Born takes little Pascal to see the cramped east London council flat he grew up in. "We didn't have much," he says. "It was dusty and mouldy and I remember toilets flooding all the time. It was a bad place to live."

"I feel fortunate that I can give my kids something different. We don't know if it's going to work, all we can do is try, but I feel so lucky to be able to do that."

SHOPPING TURNS SERIOUS

Elinor assumes responsibility for decorating the home, which quickly proves a challenge. "It’s hard to understand what's inside certain products. Nothing tells you if it's potentially going to be poisonous!" she says.

Hours are spent searching for solvent-free paints, formaldehyde-free MDF panels and flooring low in VOCs (volatile organic compounds) which slowly release chemicals and produce a charming cloud of toxicity that ends up in our lungs.

"I can't smell anything, it's really awesome!" says Born, when the white paint chosen for the walls arrives.

The floor finish is dust-free, black polished concrete and the carpet in the bedrooms is made from bamboo, with no nasty glue lurking on the reverse

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UNDER PRESSURE

Ten months later and with just weeks to go until Christmas, crack of dawn starts become the norm. Everyone is working flat out to put the finishing touches on what looks like a humble scouts' house from the front, but triples in size to reveal a sleek, contemporary family home as you walk around the corner.

But, of course, the real test will be the effect on the children's allergies once the move in.

"I've watched hundreds of people build a home to try and improve their lives. But for a building to actually have a physical effect on our health is something else," says Kevin, as he returns after the family have been living here for six months.

FIRM THUMBS UP FROM KEVIN

Immediately, he feels suspended in mid-air by a glass walkway in the entrance hall, which leads into a fabulous open-plan living space that feels bigger than it is thanks to the bolted ceiling and three huge windows that draw the outside in.

"It's a shed on the outside, but sheer joy and luxury on the inside," he remarks, admiring how the elegant decorations complement the sturdy masculinity of the polished floor and black exposed beams.

"We wanted to amaze without overbearing," says Elinor. "It's a brand new house. It needed character."

Finding a suitably 'healthy' sofa proved a struggle as brand new ones release chemicals due to foam and glue. Instead, they opted for a second-hand one which has already released chemicals elsewhere, and have cosied things up with knotted and woven rugs.

As the glazing increases, the light gets softer, and the colour scheme darker. The kitchen is a trendy, moody blue, while downstairs, the bedrooms are bathed in a wonderful golden glow come evening courtesy of the biodynamic lighting.

The tranquil master suite enjoys a view of a South of France style courtyard filled with air-purifying plants and the family bathroom is spa-like and serene. "I'm not normally jealous of people’s bathrooms but that is very special," says Kevin.

This is an imaginative piece of architecture brimming with colourful surprises, but it is when Born pulls out of one of the air filters to show Kevin how much dirt, dust, spores, mould, insects and exhaust particulates it is trapping, that we're reminded of the driving force behind it.

THE PROOF IS IN THE PUDDING

Since moving into their new home, the boys have had "only one or two" allergic reactions, as opposed to a minimum of one attack every other week.

The University of York has lent Born and Elinor a VOC monitor to assess their air quality. It shows that their home is performing over 70 per cent better than the average new build.

They went over budget by £60,000 due to Brexit hiking the price of everything ordered from Europe up by 6 per cent, but it’s been worth every penny.

"It's been a roller coaster ride but we feel really proud," says Elinor. "The moments that we get to sit down, reflect on what we've done and enjoy the house, and see the children enjoying the house, are priceless."

It only seems right that Pascal has the final, pertinent say:

"I like the house because I like the colours on it."

Grand Designs airs at 9pm tonight on Channel 4