Kieran Long and Piers Taylor follow the progress of Jo'ann and Andy, who are attempting to build a home from scratch that will never produce a heating or electricity bill. Bare concrete floors and breeze block walls are helping the budget, but will their compact residence feel more basic bunker than family home? As well as taking them to an award-winning eco-home in Nottingham, Piers encourages them to design a lighting scheme with a sheet of acrylic and a £5 light fitting. However, as their budget runs low, decisions on where to invest and where to save become tricky.