In the first 'healthy' home project ever seen on Grand Designs, gallery owner Elinor and fitness entrepreneur Born set themselves the near impossible task of creating Britain's first hypoallergenic house in a leafy back garden plot in south west London. Driven by the need to alleviate their two young sons' life-threatening allergies, their new part-submerged, shed-inspired home, will be constructed using low toxin materials and deploy cutting-edge filtration systems to clean the air they breathe. Right from the start, Born and Elinor are up against it, with access issues to their plot and the need to be super strict concerning suitable materials. It's an immense burden and with the children still suffering weekly allergy attacks, a race against time to get moved in. But will their innovative new house deliver the benefits Elinor and Born are hoping for?