Bronwyn Barry from One Sky Homes explains the evolution of windows and why modern windows are really pieces of equipment. She also shares what's involved when it comes to choosing high performance windows for a project.

Jason Orme, editor of Homebuilding & Renovating, shares some of the key challenges that self-builders face and what can be done to make sure they don't become pitfalls. He also explains how custom build might be a good option to explore for those who want a bespoke home but without the same level of risk.

Cath Hassell from ech2o consultants shares why saving water - particularly hot water - is something we should all be doing. She also explains how we can achieve this in our houses through a mixture of technical solutions and behaviour change.

*A lot of the information in this episode is specific to the UK. This is because it became difficult to keep answering in general world terms because in each country it would be slightly different.*

Lloyd Alter, Managing Editor of TreeHugger, explains how worldwide trends in green building have developed. He also shares his tips for self build success as well as some pitfalls to avoid.

Architectural designer Wilf Meynell explains the concept of environmental design and why it is not the same thing as low energy design. He also shares how he has tried to balance these two approaches in one of his upcoming projects, Springfield House.

Douglas Kent from The Society for the Protection of Ancient Buildings explains how to look after period properties and what advances are being made with conservation techniques in order to achieve greater energy efficiency.

Tim Hulse from EcoVert Solutions explains what insulation is and why there are often trade-offs to be made when selecting insulation.

Architect, planner and author Graham Towers explains the fundamentals of housing density and why we really need to get it right in future developments.

Mark Wilson from BuildingDesignExpert.com shares why he believes there is no such thing as a sustainable material and why it is our environment we are really hoping to sustain.

Architect and author Sarah Susanka shares why scale is such an important aspect to consider when building a house. She also explains how a 'not so big' philosophy can be applied in many areas of our lives.