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.

Jake White from Ecotecture shares the story of The Curly House, an award-winning project that was built using insulated concrete forms (ICF). He explains what an ICF is, why there are benefits in terms of speed of construction and durability, and why most concrete structures have the potential to be extremely airtight.

Rory Bergin from HTA Design LLP explains why building standards are devised, the pros and cons, and why people adopt voluntary standards. He also gives an overview of the Active House standard.

Dusty Gedge, founder of Livingroofs.org, explains the benefits of installing a green roof, how it can be simple and why lots of people get swayed by commercial systems.

Graham Hunter from Parity Projects explains how data collected from one of their energy assessments is then turned into a report of options for the homeowner. This follows on from episode 60 which trailed Graham as he conducted an assessment.

Stephen Gurney from Ecological Building Systems explains the main causes of poor airtightness test results.

Alan Budden from Eco Design Consultants explains how simple design decisions can drastically alter the energy performance of a house and why this means your designer needs to be using a tool like the Passive House Planning Package (PHPP) to better inform these decisions.

Ken Levenson from 475 High Performance Building Supply explains what overheating is, why it happens and how to deal with it.

Doug King explains what smart energy systems are, how they work and whether we should be embracing them in our new homes.

Building services engineer Alan Clarke explains what factors should be considered when choosing a heating system for a low energy home.

If the idea of going 'off-grid' excites you, then perhaps now is a great time to be doing it. We live in an era where the cost of items such as solar panels is continually dropping and this is juxtaposed with fossil fuel reserves that deplete day by day.

While you may even be forced off-grid if you move to a remote location, does it make sense going off-grid if you have perfectly good access (for example, in a town or village)? And with different grids -transport, gas, water - which is the easiest to unplug from?!

In this discussion (which was one of our Google+ Hangouts) we discuss some of the issues surrounding going off-grid.

The Panel

Mike Coe, who lives in the Cropthorne Autonomous House (and was our guest in episode 54).

Paul Scheckel, author of The Home Energy Diet and The Homeowner's Energy Handbook.

Ken Silverstein, an business journalist who specialises in writing about energy

Graham Hunter from Parity Projects conducts an energy assessment of a country house. He talks through the process as he goes about it and explains how the collected data will be used.

Andrew Farr from Green Building Store explains what qualities mechanical ventilation with heat recovery (MVHR) should bring to a house. He also shares how to make sure you get a system that is properly designed, installed and commissioned.

Chris Parsons from Parsons + Whittley architects shares his experience of the costs behind Passivhaus.

Interview with Chris Parsons

Chris Parsons from Parsons + Whittley architects has always had a focus on making buildings as efficient as they can possibly be. With the issues around global warming and trying to reduce carbon emissions, this is why they found a great synergy with Passivhaus.

Joe Atkinson explains how the LILAC cohousing community came together and why their project is affordable for everyone.

Piers Taylor from Invisible Studio Architects explains what a build system is, why you would use one over another and whether any are preferable when it comes to creating low energy houses.

Steve Mouzon from Original Green helps answer a question (from Frank Wiley) about what houses we should be building in areas that are prone to hurricanes or other extreme weather.

Mike Coe lives in an autonomous house with his partner Lizzie Stoodley. He shares the story behind this self-build project and why it’s ultimately left them with a deeper connection to their environment.

Mark Tiramani, the self-builder behind the UK’s first certified Passivhaus, shares his experience of building Y Foel and how this got him interested in the Passive House Planning Package (PHPP). He explains what PHPP is and why it’s a valuable tool.

Lisa Ann Pasquale from Six Cylinder Limited explains what thermal imaging is and how it can be used in quality assuring the construction of low energy buildings.

In this special episode Ben Adam-Smith explains why he wants to crowd-fund a documentary about airtightness, what it will entail and how you can help.

David Snell, author of Building Your Own Home, shares advice on acquiring land, building up a skilled and reliable team, and keeping contracts simple. He is currently building his 14th house!

David Rudlin from Urbed explains what collective custom build is and why it would be beneficial to build more houses this way.

Sarah Lonsdale, an eco columnist for The Telegraph, shares a list of 30 home improvements she has made to reduce energy bills, and save energy and water. Ultimately Sarah would like to build a new home (such as a Huf Haus or Passivhaus) but in the meantime she explains the benefits of incremental upgrades.

Ian McKay from BBM Sustainable Design shares how to find a property that will lend itself well to an eco retrofit.

He also contrasts two very different projects, the retrofit of a 1960s terraced house and the upgrade of a Victorian villa from the 1890s.

Diana Woodward explains how her house was first modelled on a computer and then the 3D digital information was transformed into exact physical replicas. The components were fabricated out of WISA board on-site using a mobile manufacturing facility.

Upgrading your property so that it is more comfortable and costs less to run makes sense. If we're serious about tackling climate change then retrofitting has to be undertaken on a huge scale. So if it looks good on paper, why are very few people doing it?

In this discussion (which was one of our Google+ Hangouts) we consider some of the barriers that may be putting people off.

Mark Siddall from LEAP (Low Energy Architectural Practice) explains the circumstances under which poor ventilation can occur and why the control strategy becomes increasingly important the more airtight the building is.

David and Penny Learmonth share their experience of building an ultra low energy home on a budget. They also project managed this themselves.

Fran Bradshaw from Anne Thorne Architects shares her experience of building an ultra low energy home using natural materials such as straw bales, lime render and clay plaster. The house is also aiming for the Passivhaus standard.

Ben Adam-Smith looks at some of the essentials that you need to understand if you are going to create an energy-efficient house. There is more detail in Ben's new e-book: Why Most People Don't Build Energy-Efficient Homes.

Martin Holladay from Green Building Advisor talks about the pros and cons of the Passivhaus standard. He also explains why he believes the German standard is not the best approach for the North American climate.

Mark Elton from Sustainable BY Design explains what a phased retrofit of a house entails and the steps necessary to make it a comprehensive set of measures. He also shares his views of which properties make the simplest and most cost effective retrofits.