The benefits of natural materials for CLTs

Our community building coordinator Josh writes about why natural materials offer a significant opportunity for Community Land Trusts like OCLT to tackle the environmental crisis while achieving their key goals. (For more on how OCLT is integrating natural materials into its work, see our page on the collaborative Regenerative Community Building project.)

Using natural materials to construct (affordable) housing has many potential benefits. Here, we'll focus on two groups of these benefits that are particularly relevant for Community Land Trusts like OCLT: their environmental benefits, and their soci0-economic benefits.

The environmental benefits of natural materials

25%: total UK carbon emissions attributable to the built environment (source)

50%: the portion of raw materials extracted globally for which the construction sector is responsible (source)

500 million: the number of tonnes of waste accounted for by products made from cement (i.e. buildings) in Europe; this is equivalent to ⅓ of all the continent’s waste (source)

To meet UK government targets, 1.5 million homes will need to be built in the next 5 years, and 1 million homes will need to be retrofitted every year until 2050. The second of these targets is intended to enable the UK to reduce net greenhouse gas emissions to zero by 2050. But there is a risk that, if we continue to build using the materials that have dominated construction over the last century, we’ll miss the proverbial wood for the trees.

There are two main reasons for this.

First, because these mainstream materials frequently take a lot of energy to produce and transport to construction sites, resulting in carbon emissions before homes are even built. This “embodied energy” of buildings needs to be taken into account alongside buildings’ “energy performance” (i.e. how much energy a building takes to heat, light, ventilate, etc.); a narrow focus on only the second of these could actually result in higher carbon emissions overall.

Take concrete, for example: the production of one tonne of cement – a key ingredient in concrete (along with sand and gravel) – results in the emission of approximately one tonne of CO2 into the atmosphere. This makes the cement industry responsible for 5-9% of our total carbon emissions. As the Guardian reported in 2019, “if the cement industry were a country it would be the third largest dioxide emitter in the world, behind the United States and China”. In 2018, a staggering 80% of the mass of all new construction in the UK was concrete.

Second, because the production of these mainstream materials often damages the environment in other ways that aren’t captured when we look at carbon emissions alone. These can then have a knock-on effect on nature’s ability to reabsorb carbon from the atmosphere.

To return to the example of concrete: producing the cement in concrete is responsible for about 9% of the world’s industrial water use, and it’s estimated that by 2050, 75% of this water use will be in regions experiencing water stress. Water stress means less water is available to sustain ecosystems, particularly aquatic ones, but also ecosystems managed by humans to produce food (e.g. through irrigation). These are ecosystems that sequester carbon when they are working properly, but can dramatically lose this ability when under stress.

Fortunately alternative, “regenerative”, ways of building using natural, minimally-processed materials are being developed. These not only significantly reduce the negative impacts mentioned above, but also help regenerate our natural ecosystems so that their biodiversity and ability to capture carbon from the atmosphere actually increases.

Take the use of hempcrete for example. Hempcrete – a mixture of hemp and lime that is highly insulating – can actually be carbon negative as long as 20% or more of the mix is hemp. This is possible not only because hemp plants absorb twice their own mass in carbon dioxide from the atmosphere as they grow, but also because the lime in hempcrete gradually absorbs carbon dioxide from the air over time, so that even a finished building incorporating hempcrete will continue to reduce atmospheric carbon dioxide.

And studies so far suggest that growing hemp can have positive effects on biodiversity when compared with other crops; this is the subject of ongoing research here in the UK.

The socio-economic benefits of natural materials

So there are compelling environmental reasons to use regeneratively-produced natural materials like hempcrete in our buildings. But these materials have additional advantages over mainstream construction materials that enable Community Land Trusts to fulfil two of their key social values: empowering local communities, and building up their wealth.

Community Land Trusts (CLTs) function by putting land and other land-based assets into community ownership, in perpetuity, so they can be used to benefit the local community. They do this because it’s an effective way of transferring power back into community hands, and taking it out of the hands of others (e.g. private owners, corporations, asset managers) who may not have the community’s best interests at heart. This power can enable land to be used for purposes like building affordable housing, which may be crucial for the local community – for economic, social and environmental reasons – but blocked or sidelined when other interests hold sway.

And, importantly, this means that the wealth this land generates, for example through rents people pay to live there, goes back into the community rather than being skimmed off for the benefit of distant asset owners or shareholders.

Empowerment through making use

So community empowerment is partly achieved by CLTs through community ownership. But enabling communities to use land in ways that benefit them involves more than just giving them ownership over this land; they also need the skills, tools and other resources to be able to make use of this land, for example by building on it.

Take housing, for example. Look at a cross-section of a typical house built out of conventional materials – especially an energy-efficient one – and you’ll see that it’s a comparatively complicated thing, often formed of various layers of materials, some of them quite technical. These materials are frequently expensive, there are a lot of them, and it takes a long time (and a lot of skill) to learn how to combine them to build watertight, energy-efficient, durable homes. They also often require sophisticated tools to employ.

It would be difficult – both expensive and time-consuming – to equip members of the local community with the skills, tools and other resources to build in this way.

With natural materials, by contrast, community empowerment of this kind tends to be easier. There are a few reasons for this:

Many natural materials are comparatively easy to learn to use for construction.
The construction of buildings made of natural materials is often simpler than that of buildings made using conventional materials.
The tools needed to construct natural buildings are comparatively simple and low-tech.
Most natural materials used in construction are non-toxic and non-hazardous, so lower levels of PPE and training are required to use these materials safely.

And, if community members can be trained up to build their own housing using these materials, this is another way of keeping wealth in the local community itself.

Community wealth building through production

Natural materials also have the advantage that they can be produced locally, which means that the profits from this production can remain within the local economy. For example, a local farm might produce hemp for house building, employing local people and boosting the local economy by doing so. Local communities may even be able to set up their own material production by acquiring land for growing, for example, retaining profits entirely for community benefit. Or they could develop partnerships with local producers who they know are working in ways that give back to the community (non-profit and/or cooperative businesses, for example), perhaps even striking deals with these producers if the materials are to be used to build affordable housing.

This scenario is much harder to imagine when it comes to many conventional building materials such as concrete, for example, or petrochemical-derived insulation, which are derived from raw materials extracted at significant distance from the point of their use, often by multinational companies who retain the profits from their sale.

So when it comes to building up the wealth of local communities, natural materials offer an opportunity that conventional materials may struggle to provide.

Natural materials: the future for CLTs?

The creation of affordable housing, which has so far been one of CLTs’ primary goals, is still largely achieved through conventional means. Natural materials are understood to be more expensive than conventional materials like steel and concrete, and the skills to use them in construction are thin on the ground – not to mention the supply chains needed to get them to construction sites. So despite their immense potential, there are significant challenges that lie in the path of natural materials’ more widespread adoption for affordable housing.

But one of CLTs’ main advantages is their agility and ability to experiment with innovative ways of getting things built – from involving community members in construction to keep costs down, to forms of community financing and partnership building. In Dorset, for example, Bridport Area Community Housing has partnered with other organisations on the Raise the Roof project, which has explored how to create affordable homes out of local, natural materials. Meanwhile We Can Make in Bristol is exploring how to use more “homegrown” timber in affordable housing. And in York, YorSpace are creating new affordable homes according to “One Planet Living” principles, committing to use natural, low-carbon materials in their projects.

Inspired by their example, OCLT has established its own partnership with researchers from Oxford’s two universities to explore how it can integrate more natural, regeneratively-produced materials into its own projects. You can find out more about this partnership, which was formed through Oxford University’s Science Together programme, on our Regenerative Community Building project page.