Mark Chesney from Beam Vacuum & Ventilation explains how houses have become increasingly airtight and why this has had a significant impact on energy efficiency. He also shares why having a good ventilation strategy is so important.

John Butler tells the story of how he retrofitted a bungalow to be more energy efficient. Having carried out a lot of the work himself, he also shares what he's learnt about airtightness and overheating.

Jackson Moulding from Ecomotive tells the story of Ashley Vale, a group self build scheme in Bristol, UK, that initially had to fend off a large developer in order to secure a plot of land. The will of the local community was instrumental in making this happen.