Geoff Wilkinson looks at issues surrounding the use of natural construction materials
As we start to look at a return to normal from the coronavirus lockdown, materials supply is at the forefront of the construction industry’s thoughts at the moment. The reliance on products produced overseas and imported into the UK has caused serious issues. With pressure also on to reduce the total carbon footprint of buildings (including its transportation), architects may well be looking at alternative products.
Natural resource extraction has increased 45 per cent since 1995 and sits at 60 billion tonnes per annum, with rich nations using 10 times the resources of poorer ones. Construction materials account for 20 per cent of the UK ecological footprint and greenhouse gas emissions and a staggering 30 per cent of all UK freight transportation.
A lot of focus is placed on the use of timber to help offset this and global demand for timber is expected to increase dramatically, as it can be used as a sink to embed carbon within buildings. Unfortunately the reality is that a lot of this timber will simply be used in short-life products such as fencing and pallets, which effectively release the carbon they have stored relatively rapidly either through decomposition in landfill or more instantaneously through being burnt. Additionally, much of the timber used in the UK is imported and, once the transport emissions are added, timber ceases to be as positive an option as it might first appear.
A great way to address all of the issues raised above is to use traditional local natural materials such as timber, straw, hemp, earth, and so on. Some of these materials are from abundant sources and are extremely reusable. Other natural materials can be grown here in the UK, and are therefore from a truly renewable source that is not at threat from any overseas lockdown.
Many eco-building methods use low-value by-products of agricultural production. Building with hemp, for example, uses the ‘shiv’, the inner core of the hemp stalk (pictured top). Hempcrete can be made by mixing hemp shiv with a lime-based binder. Hemp is easy to grow, increases local biodiversity and needs little or no fertiliser. Using it is also an easy skill for trades to learn.
Unfired earth also has a low carbon footprint, because very little energy is needed to extract, transport and work it. While earth is not an insulating material, it is a great way to provide thermal mass to buffer heat. This makes it a good alternative to concrete blocks or bricks for internal walls.
Unfortunately, the Building Regulations don’t currently detail the use of these forms of construction and rigid interpretation of regulatory requirements can stand in the way of their adoption. We recently had a client wanting to use natural cork as an exposed insulative product, but found that it was almost impossible to source a material that had been tested for surface spread of flame. Trying to find a manufacturer that supplied a treatment to improve its performance was equally difficult.
UK construction waste produced per person is more than double the collected household waste
While new materials are difficult to get approved and tested, upcycled material is even more difficult. Astonishingly, UK construction waste produced per person is more than double the collected household waste. If we are to create a truly sustainable future, regulations need to change to ensure that only recyclable materials are used.
To this end, readers may be interested in the EU project Buildings as Material Banks and the creation of ‘material passports’. There are already about 300 products with material passports, providing information for a circular use of building materials, products and components while supporting reversible design.
Currently there are numerous product labels and assessment schemes available on the market. These address various aspects (environmental, health, etc), life-cycle stages (eg resource extraction), geographic regions or different types of materials (eg non-renewable/renewable). If these often-voluntary and disparate labels were brought together within a common data set and embedded within the regulatory sign-off process, it could quickly speed up the adoption of such techniques. Alongside offsite manufacture from a standardised and pre-approved set of building components, this could transform the UK construction industry.
Will the government have the foresight and courage to bring this into the next iteration of the Building Regulations? Or will the tightening of testing requirements proposed under Judith Hackitt’s proposed reforms result in the reverse, with only new materials able to satisfy the strict testing regime? Only time will tell.
Geoff Wilkinson is managing director of Wilkinson Construction Consultants