Sustainable Architecture Blog: Should we retrofit or rebuild Britain’s housing stock?


Reassessing our built environment is vital in the fight against climate change as about 45% of CO2 emissions in the UK come from energy used in our homes and buildings. It is vital that the government looks seriously at how Britain can reduce these emissions. But should we retrofit or rebuild Britain’s housing stock?

There are a host of pros and cons to both approaches, and neither is cheap in the short-term. Like most sustainable technologies, reducing the greenhouse gas emissions of a building is a long-term investment. However, the built environment accounts for over 40% of global carbon emissions so it is imperative that reducing this becomes a focus of the international agenda. With climate change looming and energy prices rising, our built environment risks being our greatest liability.


As sustainable building methods become more advanced and efficient, new housing will increasingly impact less on the environment. This is why advocates of rebuilding Britain’s housing argue it is better than retrofitting as a long-term approach to reducing housing sector emissions. On the whole it is much easier to build a passivhaus from scratch than adapt existing housing. Indeed, the cost of refurbishing and maintaining existing homes can often exceed the home’s value.

Sustainable re-building requires low embodied energy and excellent insulation. A new structure that is well insulated with low embodied energy can have a negligible carbon footprint. The environmental impact of demolishing an existing building, especially one that contains little or no wood, can be severely reduced by disposing of the materials responsibly.

However, if large amounts of wood are burnt or allowed to rot carbon is released into the atmosphere (whereas, the carbon in wood can theoretically be locked up in landfill). Architects could incorporate reclaimed timber in their designs to offset these emissions, or even re-use the materials from the original building. The carbon in wood can be stored if it is well maintained.

This technique of locking up carbon within buildings is known as carbon sequestration. This can also be achieved by using buildings materials such as hemp, other biomass and reclaimed building elements.

‘Jobs, Growth and Warmer Homes’, a report by Consumer Focus in 2012, looked at how the UK government should re-invest money raised through carbon taxes and energy efficiency. Responding to these findings, The Energy Revolution argued that the UK government must invest the money by re-building houses. The fuel poverty alliance, the biggest of its type, commented that:

This report shows that in its bid to boost UK economy, the Government is not investing in the one thing which could create more jobs and growth than anything else – re-building the UK’s housing stock. Not only does this have massive economic benefits but it is the most effective way to bring down energy bills.”


Rebuilding the housing sector might not be high on the government’s priorities (although targets have been set to make all new builds from 2016 carbon neutral), but eco-refurbishment certainly is. One of the UK government’s main strategies to reduce greenhouse gas emissions is to make homes more energy efficient. Their flagship policy to tackle home energy efficiency is called the Green Deal. Launched in January, this is a financial investment to make buildings more energy efficient, and is also designed to reduce fuel poverty.

Retrofitting involves the addition of new technologies and materials for the benefit of the property. For instance, improving insulation makes a building more energy efficient and therefore more sustainable. Energy efficient retrofitting is also a rapidly growing market because of the savings that can be made, and it is a much cheaper strategy in the short-term than demolishing and rebuilding properties.

But what should be Britain’s approach to be?

The UK has a tougher choice then developing nations because more of the built environment in newer countries is still to be constructed. This means developing economies can set the tone for sustainable development in a way that the UK cannot. British architects must also consider the cultural worth of historic buildings that already exist. Georgian townhouses may look impressive and have a great sense of heritage, but they can also have woefully inadequate insulation, ineffective heating and aging plumbing.

The Zero Carbon Britain (ZCB) project, a scenario for a carbon neutral United Kingdom by rapid decarbonisation, supports retrofitting the majority of the British housing stock. The researchers propose using natural materials where possible to eco-renovate buildings. Hemp shiv would be an ideal substitute for artificial insulation because it is proven to be resistant to moisture ingress. The hemp used in this insulation could also act as a carbon sink.

But this model is not possible for every home. Writing for the Guardian, Tony Hutchinson argues that:

Looking at the total cost of a refurbishment project over its lifetime (including maintenance and eventual replacement) in both cash and carbon terms the outcome can be very different. Cost and benefit modelling should be used to compare the benefits of demolition and new build with the costs of maintenance of the retrofitted building over its useful life – and the cost of further refurbishment after 30 years or complete replacement.”

So if we are hoping to build truly sustainable communities for the future, developers must look at the long-term. Where possible, Britain should rebuild its housing stock. This will take time, however, and may not be possible by ZCB’s target date of 2030.

Modern architects must be bold during this transition. Many of Britain’s houses will be too expensive to eco-renovate. If historic buildings such as Victorian and Edwardian terraces must be protected, then why not keep the facade but demolish the living spaces behind? A sustainable structure constructed in its place can be integrated with the historic face of the building. Projects like Kings Cross10 Hills Place and others demonstrate that this is achievable. Obviously there will be instances where this is not possible, but architects and eco-builders must think outside the box to find creative ways to decarbonise Britain’s buildings.

ZCBlog: Volunteering for a sustainable future!

Volunteers are extremely important to the Zero Carbon Britain project. As the research nears completion the long-term volunteers are beginning to look at how best to communicate ZCB to the people that will have to embrace a sustainable future: the public.

Two new long-term volunteers, Sarah and Megan, are working hard to support CAT and the ZCB team in both research and communications.

Sarah Everitt has been working with the ZCB team for a few weeks now. She is enthusiastic about making an important contribution to a project that has the potential to vastly benefit not only the UK environment, but the global climate too.

At the moment, now that the research is coming to a close, she is working to improve the report’s structure. Sarah is putting together a template that can improve accessibility of the new report to a wider audience. This is not such an easy task, with a scenario covering a variety of topics and  complex research data, but key to communicating ZCB to the general public.

Megan Jones joined the CAT team last week from the Isle of Anglesey, Wales, where for the last three months she has been a Residential Volunteer for the RSPB at South Stack Cliffs. She came back to Britain last autumn after finishing a BA in English at Reed College in Portland, Oregon, USA.

“Ever since I was a kid I’ve loved exploring woods and mountains (so mid-Wales is pretty perfect for me), and I’m hoping to make a career inspiring others to love nature and protect biodiversity. I’m very much looking forward to being a long-term volunteer at CAT, where I’ll be sharing CAT’s stories through social media, gaining new skills in marketing, and helping bring the new Zero Carbon Britain report to fruition.”

The Centre for Alternative Technology’s achievements over the last 40 years simply wouldn’t have been possible without the hard work, inspiration and dedication of the volunteers. With Nuria leaving at the end of February and a new volunteer starting in the coming month, ZCB’s volunteers have been invaluable to the evolution of the project.

Both Megan and Sarah are helping to co-ordinate a series of discussion papers titled ‘ZCB and…’ These will explore how the Zero Carbon Britain scenario effects wider topics beyond the team’s core research. Read more about the project here.

The Green Deal – What you need to know

On the 28th January the UK Government launched the Green Deal, aimed at making UK homes more efficient and helping households reduce their energy bills. Ever since the scheme was announced it has divided opinion; some people have lauded the scheme as a step towards UK-wide energy efficient homes, others criticised the workings of the deal as not being in the best interests of the consumer. Rather than debating the merits and criticisms of the Green Deal, this post summarises five arguments for and against the scheme.


1. Incentive to make homes more energy efficient

The UK has some of the most inefficient housing stock in Europe. It is estimated that 19% of UK householders (4.75 million homes) spend over 10% of their income on heating. This is classed as fuel poverty, and the number of people affected grows every year. The Green Deal will help people invest in their homes, making them better insulated and more energy efficient.

2. Savings on bills

The Green Deal is essentially a long-term loan, with repayments taking up to 25 years. The difference between the scheme and a regular loan is that the repayments are made through people’s energy bills. Having a more energy efficient home should result in a lower bill, thereby saving people money.

3. Customers protected by the Golden Rule

The Green Deal has a ‘Golden Rule’: the repayments made through the energy bill will never be more than the savings achieved by undertaking the improvement works. This protects the customer from expensive repayments that would cost more than the benefits gained.

4. Long-term benefits

Energy prices are set to rise in the future. As heating and electricity become more expensive, reducing costs by improving the efficiency of the home is key. Although the Green Deal should reduce bills from the get go, it will be even more important in the long-term, with savings increasing as energy prices rise.

5. Finance available

The Government has pledged £40million as part of a cash back scheme as an incentive for householders.



1. Based on average, not tailored to households

Before signing up to the Green Deal an Assessor will make suggestions that will lead to greater energy efficiency. Their calculations, however, are made using UK-wide data and are not tailored specifically to the house in question: the actual savings could be less than those predicted. Furthermore, the mean temperature suggested is 21⁰C for main living areas. If householders choose to maintain their homes at a lower temperature they will still have to pay back the loan equivalent of keeping their houses at a higher temperature.

2. Relies on predictions of future energy prices

Although the scheme should save householders money off their energy bills in the short-term, the cost of energy in the future has been a key part of the Green Deal. This relies on estimations of energy prices in the future, something we cannot predict.

3. Early re-payment fees

In most circumstances it should be possible to pay back loans early. However, Green Deal providers may be able to charge an early repayment fee as compensation for the loss of interest they would have accrued over time.

4. The interest rate

The interest rate for repayments will be market-led, but estimates have placed the average at around 7.5%. Depending on the amount borrowed and the length of time taken to pay it back, householders could end up paying double what was originally spent due to the interest rate level.

5. Cost of an assessment

The Green Deal scheme encourages householders to have more than one assessment done of their property before deciding what improvements should be made. Most Assessors will charge a call-out fee of up to £150, reducing the number of plans a householder can choose from.


The Whole Home at CAT


Sustainable Architecture Blog: Should buildings be green or sustainable?

Last week the blog looked at the future of sustainable architecture, this week we explore the differences between sustainable, green and natural architecture. Sustainability appears to be a much more popular concept in professional circles than it is being green. So should architects distance their designs from being labeled as green?

In recent years, the prefix green has become increasingly unpopular, particularly in professional circles, in promoting environmentally responsible architecture.

But what does green mean? The word brings to mind a wide range of associations. It has grown to be synonymous with environmentally-friendly lifestyles. But for many, green simply means that the end product minimises effects on natural resources; producing less waste in the process.

A lot of the backlash against using the word green stems from the trend to promote businesses and brands as environmentally friendly, even when they are not. This practice is known as ‘Greenwashing‘. Fortunately many of the underhand tactics used to make businesses appear environmentally responsible, have now been curtailed by international advertising standards and regulatory bodies. However, it seems that architects prefer to promote their designs as sustainable rather than green.
In recent discussions with architecture students, both AEES postgraduates at CAT and undergraduates from other colleges, the opinion was that the phrase ‘green architecture’ has connotations with natural building. To some it lacks precision, being more issue driven than quantitative in a measurable manner. It seems that green building is not seen as being cutting edge in the same way as sustainable architecture often is.

Natural building focuses on using local resources to negate the environmental impact of a building. These resources can include geological factors and the surrounding ecology. The use of plentiful materials that have not be treated with synthetic chemicals is often key to reducing the ecological impact. In general this means that many of the building processes are informed by historic methods of building. Therefore natural building tends to rely on human labour, more so than cutting edge technology.

Popular raw materials include stone, clay, sand and locally sourced & renewable wood. These materials can be combined to create surprisingly resilient structures. For instance, earthen architecture is one of the oldest examples of built environments. Cob, rammed earth and adobe are all examples of earthen architecture building methods.

So how does natural building compare to sustainable architecture?

Sustainability as a concept can often be contradictory and muddled. To be sustainable is be aware of the long-term; the effects of what you do on your environment and the future. To sustain is not to over-reach but to endure. In this interpretation of the definition, sustainability is about so much more than just being green.

However, a building can claim to be sustainable without being truly environmentally responsible. If a building is energy efficient then it can be argued that the structure is economically sustainable. Indeed, energy efficiency has become the over-riding consideration for much of sustainable architecture. An architect may design a building that is totally energy efficient but it might not be green. As sustainable assessment methods, such as LEED and passivhaus certification, become more popular the aim of many sustainable building projects have shifted. The aim might now be to achieve a certain rating at the expense of the environment.

An example of this is the use of concrete as a building material. Concrete has a high thermal mass and therefore, can be very efficient at storing heat or insulting buildings. This can make it very energy efficient. But the production of concrete is very energy-intensive. The concrete industry emits large amounts of carbon emissions because of transport and production. A final consideration is the fact that concrete is resilient, so the building may last a long time. The materials needed for repair might be reduced. This highlights how a construction material can be seen as sustainable but not necessarily green.

The argument for and against labeling building methods as green will continue to rage. It is obvious that professionals might not want their projects defined as being green but architects should not be afraid to label their sustainable processes as green.

By designing buildings that have a holistic approach and a green ethos, architects can consider the wider impacts on climate and environment. This must be the goal of all sustainable architecture.

Further reading:


Podcast: what will the next 40 years of the environmental movement bring?

Two weeks ago students on our MSc Architecture: Advanced Environmental and Energy Studies course came to CAT for the annual politics module. This time, the module featured discussions on everything from green economics to behaviour change, and we’ll be presenting some of these lectures as podcasts in the coming weeks.

At the end of the week, students got a chance to put their questions to an expert panel featuring CAT’s media officer Kim Bryan, CAT’s external relations officer and Zero Carbon Britain director Paul Allen and Green Party Councillor Andrew Cooper. This podcast is an excerpt from the end of the discussion, as the panel debate the main achievements of the environmental movement’s 40-year history, and consider what the next 40 years will bring. The first speaker is Paul, followed by Kim and then Paul. The adjudicator is Adrian Ramsay.

Previous podcasts

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Why Sustainable Architecture is the Future

Sustainable architecture holds the key to an environmentally positive future. Only by living more economically with our resources can we hope to protect our environment and climate. So what better way to live more sustainably than by making sure the very structure of our built environment is greener?

The philosophy behind sustainable architecture is all about reducing waste. This not only means physical waste but minimising energy loss as well. By keeping the energy we consume within our buildings for as long as possible, we need less supply in the first place. Using less energy to keep us comfortable means that we can become environmentally responsible and more resource efficient, which are both vital to reducing the effects of climate change.

Governments around the globe are looking at initiatives to make new builds and retrofits more sustainable. The Green Deal was launched in the UK on the 28th of January. This policy is a government initiative designed to persuade businesses and homes to retro-fit green technologies in their buildings. There are also initiatives such as the Passivhaus standard, which sets clear requirements for certificated buildings. As the name suggests, this approach to low energy housing originated in Germany during the early nineties. To meet the standard, a ‘Passivhaus’ must meet an energy demand target. A number of these sustainable assessment methods for architecture exist including BREEAM and LEED.

But while a building might be incredibly energy efficient, the structure’s building materials could still have a huge impact on the climate.

In his book, How Bad are Bananas, Mike Berners-Lee calculates that building a new two bed cottage produces the equivalent of 80 tonnes of carbon equivalent emissions. The majority of this impact is in the walls and the materials used. Much of these emissions can be recouped by using energy efficiency methods while the house is occupied. Yet, if sustainable building practices can reduce the impact of the construction in the first place then this is preferable if we are to become more environmentally conscious.

Construction materials such as rammed earth and building techniques like turf roofs are proven to have less impact whilst holding their own when compared to established but unsustainable methods.

So there are three overriding concerns when designing buildings with better considerations towards ecological impact. The first is the materials used for construction. The second concern is the energy efficiency of the building and the last factor to consider is the location of the building itself. The building might be energy efficient and use low impact construction technologies but this would not mean anything if the ecosystem suffers as a result of the building.

A greater holistic approach to all of these design factors is becoming more prevalent in mainstream architecture.

By looking at what builders have done in the past, forgotten construction techniques that might not be as redundant as previous generations thought, as well as cutting-edge technologies we can inform a brighter future. Our built environments will have less impact on the natural surroundings. This truly is a growing industry and the future of architecture.

ZCBlog: Discussing a zero carbon future

The new ZCB report will layout a scenario for an emissions free 2030 but one of the wider project aims is to raise awareness for a more carbon responsible society. Because of this, the new report will include a series of discussion papers about how ZCB relates to wider topics.

The third ZCB report will focus on a number of specific areas for a 2030 scenario. However, the team would like to discuss how ZCB could relate to other subjects. The ZCB project is looking for contributors who want to use the ZCB scenario to highlight how reducing carbon emissions will affect the UK. These discussion papers should tackle themes and issues that are outside of ZCB’s core research.

Sure, the ZCB team have researched how to eliminate carbon emissions in energy production and land-use but how will the scenario affect less quantifiable subjects. For instance, how would the ZCB scenario affect wellbeing? Could it create or diminish green spaces for recreation?

Each “ZCB and…” discussion paper should be no more than 1,000 words but preferably be between 600 and 800. If you wish to be involved then let us know! You can get in touch here.

Not sure what subject to tackle? ZCBlog will be featuring news articles next week that reflect what is happening in relation to decarbonising the UK.

How can we overcome political and environmental barriers for change?


The Centre for Alternative Technology hosted it’s first environmental question time earlier this month. The subject for discussion was politics. A whole host of questions were put forward by CAT’s postgraduate students and also by the general public online via twitter.

The event was part of the politics module for the MSc Architecture: Advanced Environmental and Energy Studies course and gave postgraduate students the opportunity to discuss the subjects they have been studying. On the panel were Paul Allen, project co-ordinator for Zero Carbon Britain; Kim Bryan, CAT’s media officer and a freelance writer on environmental issues; and Andrew Cooper who is chair of the association for green councilors and energy spokesperson for the green party in England and Wales.

The debate was chaired by Adrian Ramsay, former Deputy Leader of the Green Party and visiting lecturer for CAT. Here is just a taste of the impassioned debate that ensued:

Adrian Ramsay: The Green Deal is considered underwhelming and unlikely to achieve the required level of carbon reductions. What would the panel recommend as a viable alternative national scheme?

Paul Allen: I’d recommend the Green New Deal. The economic stimulus would be beneficial. Fuel prices are coming, the days of cheap abundant oil are long gone. An economic stimulus could create a huge amount of jobs and get people back to work… help get the economy back on track. So have a look, not at the Green Deal but the Green New Deal.

Kim Bryan: It’s better than nothing. At least we are trying to encourage change and… make houses more energy efficient. It is a step in the right direction.

AC: It’s not a step forward, it’s a step backwards. Now we have a policy which is going to produce less jobs and less work. Ultimately we need a compelling offer. That’s not going to happen with the Green Deal.

AC: I do wonder in reality if these things are the other way round; green politics disappear from the agenda during elections. It seems like the government has a bit of a one trick pony regarding economic stimulus. The Green New Deal is a way to move it on. Passivehaus retro-fit is what is required but there’s not enough of that work going on.

AR (putting forward a question that was asked via twitter): Could renationalising the utilities help decarbonise the energy supply?

KB: I certainly think privatising the energy supply has not done us any favours. But we need to be promoting community energy schemes, people taking more control of their energy and their usage. Behaviour change and education is a huge part of any retrofit that we do because if we don’t do that then it doesn’t lead to carbon emission reduction.

AR (via twitter): Many green topics only enter politics as election issues. How can we get politicians to commit to environment in the long-term?

PA: Well, that’s the million, million dollar question isn’t it? The experience we’ve had with the creation of the Zero Carbon Britain energy scenario… we got to launch it at the all party parliamentary climate change group. But if we want the the minister to act on it there has to be a shift in public attitude.

AC: I think green issues and green politics are mainstream at the moment but it has to got to be framed in economic terms… to be seen as a solution for getting us out of the situation that we are in. The green politics are going to get us out of the problem.

AR: What do you think has been the [green] movement’s main achievement… and where will it be in another forty years?

PA: We’ve created a whole new vocabulary. There was no such thing as renewable energy [forty years ago]. It’s moved into the mainstream.

AC: This is mainstream technology, this is the way people are going to have to live in the future; future technology. This is now technology!

The event was a great success and the hope is that future debates can expand to include other topics for discussion.

The entire debate will soon become available as a podcast on the blog.




Volunteers get a taste of CAT

Josh on Volunteer Taster Session


This week CAT welcomed some volunteers for a taster session to show them what it’s like to volunteer at the Centre for Alternative Technology near Machynlleth.

Josh from Liverpool studied business management at university, and after travelling in Australia fancied a change of direction. “I wanted to try something different and unusual, so I’ve come to CAT to learn about gardening.”

The taster session gives volunteers an insight into life at CAT before they decide to stay for a longer period of time. Long-term volunteers can stay from two to six months, and there are several different areas in which volunteers can work:

•Natural Building Materials Research

Zero Carbon Britain

• Site Maintenance

• Water and Natural Resources

• Eco-cabins Maintenance

• Gardens

• Marketing/Media

The centre also works with local volunteers on a flexible and part-time basis. Click here for more information on volunteering.

Josh on Volunteer Taster Session