The new run of the iconic property show continues. Kevin McCloud follows Britain's most ambitious self-building projects, as intrepid individuals attempt to design and construct the home of their dreams. Does good architecture have the power to heal? In 2017, Elinor and Born began building a clean-aired, hypoallergenic house in south-west London for them and their three children. Motivated by the extreme allergies and serious asthma of their two boys, they desperately hoped that the house would alleviate some of their more severe symptoms. In an unusual back-garden site with huge access issues, they planned a partially submerged, shed-like building constructed with low-toxin materials and a powerful ventilation system to keep the air in the house fresh. But construction placed rigorous demands on their decision-making abilities, schedule and budget. And even when they finally moved in, the jury was still out on whether the house could actually make their children healthier as they grew older. Now, seven years after the house was completed, Kevin returns to see what the long-term effects have been - and to finally discover if a carefully curated house really can make us feel better, and actually improve our physical health too...