Paul Jennings from ALDAS talks through some of the findings from the airtightness tests we carried out as part of our documentary.

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.

David Sharpe from Thomasons explains what the foundations are, why they must be site specific and how they could impact on the design of a building.

James and Dani McDonald reveal why they were drawn to HUF HAUS, how the process worked and why they have become very loyal to the brand.

Alex Baines talks through the plans for his semi earth-sheltered home, to be constructed to Passivhaus standard, and explains why involving the local community in the early stages was essential in gaining the relevant permissions.

Richard Oxley from Oxley Conservation explains why understanding an old house is such a vital first step to take before upgrading its performance.

Tim Nicholson reveals why he chose to retrofit rather than build new and, having selected a suitable property, what the strategy was and why. Tim has also been blogging about the experience on his website Oxford Green House.

Alastair Parvin explains how WikiHouse has developed and why it is so significant when it comes to enabling more people to build affordable, high quality homes.