The environmental impact of building materials
Most readers have heard the built environment is responsible for a significant chunk of the world’s carbon emissions.
According to the World Green Building Council, buildings account for more than one-third (39%) of global energy-related carbon emissions. Of this, 28% comes from the operational aspect – the day-to-day energy that is required to heat, cool and generate power for a building – while the remaining 11% derives from the materials used and delivered for construction.
Deploying more environmentally friendly construction methods and making buildings less impactful on the world have been pressing issues for the industry for some time. With resources stretched to their limit, finding efficient and sustainable ways to source vital materials has become increasingly important.
Beyond the obvious examples, such as fast-growing timber, there is mounting research into how greater levels of sustainability around building materials can be achieved. Many are labelling ‘living building materials’ as a potential solution.
What are living building materials?
Let’s specify exactly what we mean by ‘living building materials’, since there are different ways of looking at the subject.
Most of us are aware of ‘green walls’, where plants are grown on the side of a building, or ‘living roofs’, where a roof is planted with a layer of vegetation.
The amount of vegetation that can be used is dependent on the load-bearing capacity of the wall or the roof beneath it. But both can absorb moisture – and carbon – from the atmosphere, offer cooling for the building, provide a haven for insects and, ultimately, are pleasant to look at.
While these solutions are effective up to a point, they are limited in scope. Where the notion of living building materials gets really exciting is in the field of regeneration – materials that can repair themselves and even grow.
This technology is currently experimental, but if it can fulfil its promise, the payback from living building materials could be significant.
Examples of living building materials
Take the team of researchers at the University of Bath in the UK developing the country’s first ‘smart concrete’, using encapsulated bacteria to make structures that can heal and repair cracks and defects themselves.
According to professor Kevin Paine of the university’s department of architecture and civil engineering, about half of the UK’s construction budget is spent on repairing existing materials. This is primarily aimed at concrete, since it’s the most common material used by construction teams.
‘The great advantage of self-healing concrete is that it is repairing itself in situ’, he says.
Paine’s research colleague, Susanne Gebhard, a senior lecturer in biology and biochemistry at the university, says bacteria added to the concrete creates calcium carbonate – limestone – as it grows.
As it finds its way into cracks within the concrete, the resulting calcium crystals fill in and seal those empty spaces.
Meanwhile, in the U.S., a team of researchers led by Wil Srubar, associate professor of architectural engineering and materials science at the University of Colorado in Boulder, is exploring the potential for ‘living buildings’.
‘Imagine architects using genetic tools that encode the architecture of a building right into the DNA of organisms’, Srubar says, ‘which then grow buildings that self-repair, interact with their inhabitants and adapt to the environment.
Srubar’s team used photosynthetic cyanobacteria to help grow a structural building material – and they kept it alive.
‘Instead of emitting CO2, cyanobacteria use CO2 and sunlight to grow and, in the right conditions, create a bio-cement. [This] we used to help us bind sand particles together to make a living brick’, he says.
The researchers went further. By keeping the cyanobacteria alive, they were able to produce bricks that effectively grew.
Says Srubar: ‘We took one living brick, split it in half and grew two full bricks from the halves. The two full bricks grew into four, and four grew into eight. Instead of creating one brick at a time, we harnessed the exponential growth of bacteria to grow many bricks at once – demonstrating a brand-new method of manufacturing materials.’
What are the challenges of adopting living building materials?
Exciting as it is, the research being conducted in Bath, Boulder and elsewhere is still far from providing solutions that can be rolled out in sufficient volume to be useful to the construction sector right now.
Srubar says the field of engineered living building materials is ‘in its infancy’. with challenges including ‘cost, testing, certification and scaling up production’.
Srubar highlights another issue, that of consumer acceptance. ‘For example, the construction industry has a negative perception of living organisms. Think mould, mildew, spiders, ants and termites. We’re hoping to shift that perception.’
Researchers working on living materials also needed to address concerns about safety and biocontamination, he says.
And while scientists work to develop more sustainable and responsive materials like ‘living bricks’, others are addressing how to prevent buildings from making their occupants ill.
Could living materials help solve ‘sick building syndrome’?
The U.S. Environmental Protection Agency says the term ‘sick building syndrome’ (SBS) describes ‘situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified’.
According to the UK’s National Health Service, the most common cause of SBS in office buildings is poor ventilation or poorly maintained air conditioning systems, followed by dust, smoke, fumes or fabric fibres in the air; bright or flickering lights; problems with cleaning; and the layout of office space, such as crowded desks.
While the use of mechanical air circulation technology has played a part in manifesting SBS over the years, nowadays many new developments make much more use of natural air circulation and fresh air to improve the well-being of occupants.
And in newly built homes, where embedded chemicals can affect residents, there is increasing use of specialist decorative paints that don’t contain volatile organic compounds, which is good news for sufferers of asthma and other allergies.
Whether it’s exploring ways to produce building materials that self-heal to avoid the need for costly repairs, or by creating healthier spaces so occupiers can live healthier lives, the construction industry and thousands of scientists worldwide are developing new technologies to create a better built environment for now and in the future.