Buildings and the construction industry have a major role to play in reducing carbon emissions. This was already well understood in 1997, when I wrote the Green Building Handbook: Volume 1 with Sam Kimmins, Rob Harrison and Paul Harrison. Since then, however, new buildings have only improved marginally in terms of energy efficiency. Making existing buildings more efficient has also had little impact.
New targets to meet improved standards for emissions are variously described as “zero carbon”, “nearly zero” and “net zero”. This confusion over terminology exemplifies the difficulty of making buildings energy-efficient; rather like the word “community”, “zero” can mean many different things to different people.
What exactly is a zero-carbon building? It might be assumed that it means a building that has no impact at all on carbon emissions. But when you search for definitions almost all of them are a fudge as most low-energy buildings still contribute to emissions through fuel or electricity use and embody energy in their construction.
A more honest approach might simply be to set targets for reduced carbon emissions by 2030, 2040 or 2050, and stop the pretence involved with slogans such as “zero carbon”. Yet although these targets may sound like a good idea, most politicians, and even many professionals, have no idea what they mean or how to achieve them.
Embodied energy
A great deal of energy is used in manufacturing construction materials and again on site. This is known as embodied energy, and though it has been well documented has also been ignored.
Simon Sturgis has done more than anyone to address this issue, as seen for instance in this article on whole-life carbon. He has also written a critique of the Green Construction Board’s Low Carbon Routemap, arguing that it needs to adopt a holistic approach that counts not only embodied but also lifetime emissions. “The total embodied content for say, blocks of flats and many non-domestic buildings, is nearer 60–65%. Passivhaus is in the region of >90% embodied,” he explains.
In 2011, the term “carbon spike” was coined in a Finnish study, where the authors showed that the energy used in initial construction to achieve a good level of operational energy efficiency is so great that it is never recovered in the lifetime of buildings constructed in a new housing development in Helsinki.
Those in favour of increased energy efficiency ignore the fact that the bulk of damage to the planet, in the form of carbon emissions, is already done when a building is constructed or retrofitted due to the energy used to create the building materials. Many of the products used tend to embody considerable energy, but energy efficiency and Passivhaus proponents will fiercely dispute this even today.
Yet reductions in embodied energy could dramatically reduce carbon emissions in the short term, not in 30 or 40 years’ time. This can be done by using low-carbon materials and building techniques, which will be explored in more detail in future articles in this series on sustainable building issues. I will also explain how current policy, materials and practice are wedded to the use of existing technology that has high embodied energy, with little concern about the damage this might be doing to the environment.
At a recent seminar on the Green New Deal, environmental activists were arguing for more environmentally friendly materials to be used in retrofit programmes. However, Dr Alan Whitehead, shadow minister for business, energy and industrial strategy, said it is essential to use “shovel-ready technologies”.
It is also unlikely that the UK government’s green homes vouchers will encourage the use of innovative materials or techniques. The argument is that we have to use existing methods and materials – even when these don’t work very well – rather than waiting for something better.
Fabric-first approach
A fabric-first approach to make buildings more energy-efficient should be a top priority, but this has not been a resounding success so far because conventional materials and construction techniques –such as brick and concrete with limited insulation – continue to be used.
The Building Regulations have been regularly updated over the past 20 years to demand greater airtightness, and increased levels of insulation. Although this may have made some difference it was soon realised that buildings were not performing as well as predicted by Standard Assessment Procedure calculations. This problem became known as the performance gap.
Excellent work by the Zero Carbon Hub drew attention to the gap, though this was not popular with the industry and the hub was shut down before it had completed its investigations into the cause of the problem. Initially the problem was diagnosed as a result of poor construction practice, and better training and standards on site were recommended. However, the hub was not give enough time to investigate fully the underperformance of materials and methods of construction having identified over 90 potential issue themes.
In 2012, a study carried out by Affinity Sutton, now Clarion, showed underperformance of up to 70% on some projects. One of the reasons cited for this was a failure to understand that different fabric and insulation materials can vary considerably in their performance.
Insulation ignorance
But there is a widespread and mistaken assumption among designers, specifiers and builders that all insulation products are much the same, and that it is only necessary to specify insulation to a certain U-value. Insulation materials are thus frequently substituted on site if the builder comes across something cheaper.
The fact that there was no guide to insulation materials led the Institute of Civil Engineers (ICE) to commission me, Latif Eshrar and Rachel Bevan to write Thermal insulation materials for building applications, published in 2019. Nevertheless, collective ignorance about insulation and how to improve building fabric has led to many unintended consequences – not simply a performance gap but damp, mould, poor indoor air quality and, particularly, overheating.
Sealing up buildings with airtight plastic membranes, sticky tape and lightweight non-breathable insulation materials can have devastating effects, leading to retrofit disasters that will be discussed in more detail in a further article.
But I will also set out how it is possible to create highly efficient buildings with low embodied energy, using innovative, low-impact materials that should move us away from the depressing situation set out above. These materials can be made from recycled and bio-based substances such as glass, waste paper, wood waste, straw, hemp, flax, clay and even mushrooms. They meet circular economy targets more easily, have much lower embodied energy, and can be much better in terms of thermal efficiency and health and pollution impacts. Most of them can be used in retrofit and new build as well.
Many organisations calling for zero carbon buildings fail even to consider that insulation or fabric are of much importance. I have reviewed nearly 30 books and reports on zero carbon and related topics, and one of the striking things about all is their complete failure to discuss the issue of improved building fabric performance and insulation. The word “insulation” is rarely mentioned and when it is, all that can be found are vague references to providing more.
Because many in the industry fail to understand the potential for reducing carbon through what has become known as fabric first – designing and specifying materials to achieve energy efficiency – they have instead preferred to focus on renewable energy as the best route to zero carbon. There is a danger that Building Regulations will in future focus on solar panels, heat pumps and mechanical ventilation rather than better fabric insulation. In the next article I will examine the impact of energy-efficiency measures on indoor air quality and health, as this is becoming increasingly important.
“Collective ignorance about insulation and how to improve building fabric has led to many unintended consequences”