Why natural building materials?
-Natural building materials can be produced and applied with minimal amounts of processing – so their carbon cost is low
-Natural building materials help to lower the energy consumption of a building, reducing its carbon footprint
-Natural building materials create a happy, healthy environment for a building’s occupants
-Natural building materials will return to the earth at the end of their lifecycle without causing undue pollution
Some common natural building materials are hemp, earth, lime, straw, wood, stone and turf.
We’re not saying that natural building materials are a good thing per se; but we do want to explain their advantages and the best contexts to use them – at the end of the day there’s no point in super-insulating a building if you’re just going to store tools in it; and wood is not sustainable if you ship it halfway round the world.
It’s all about using the right material for the right job.
All natural building materials have a low embodied energy. Embodied energy is the energy consumed over the lifecycle of a building material – in its manufacture, processing, transportation, application and demolition. For example, bricks and cement mortar have a high embodied energy because the materials are mined, extensively refined, fired in a kiln, transported large distances, applied with powered machinery and then demolished and disposed of with yet more powered machinery. All of this embodied energy translates into a carbon cost.
Compare this with a material like straw bales – they require only small amounts of energy in cultivation and processing, and the carbon cost of this energy is more than offset by the carbon sequestered by the plant itself. Straw bales can also be produced locally, and are light, so require less energy in transportation. At the end of their life, they can be easily dismantled and composted.
So, natural building materials have a low carbon cost. Certain natural building materials (like hempcrete) actually sequester carbon (they lock away more carbon than is released in their lifecycle). This is important because the construction industry is a huge contributor to mankind’s CO2 emissions – production of cement alone accounts for 5% of man-made CO2.
Natural building materials tend to be breathable – they absorb and release water vapour and so they regulate humidity levels well. When the air is humid, they absorb moisture; when the air is dry, they release moisture. This breathability prevents many of the problems associated with humidity levels in modern buildings such as excessive dampness, condensation and mould growth, or health problems caused by very dry atmospheres.
Modern mainstream building attempts to create impermeable barriers to the outside world – but in shutting the weather out, levels of humidity and indoor pollutants can become excessive. A common result is Sick Building Syndrome, with symptoms including fatigue, loss of concentration, nausea and irritation. Certain modern building materials also slowly release chemicals which are harmful to health, a process known as offgassing or outgassing. Natural building materials release no harmful chemicals and regulate humidity by allowing the slow passage of water vapour. The overall result is a space which is conducive to human health and happiness.
Natural building materials undergo minimal processing. When they are in situ they are still obviously components of the natural world – earth, straw, wood, stone, hemp. Disposal and recycling of materials is a modern conundrum – what to do with all the concrete, plastics and synthetic insulation materials from modern buildings at the end of their life? There is no such problem with natural building materials – they can all be composted or just returned to the earth on site.
A final point to make (whilst trying not to promote natural buildings as some kind of greenwashed eco-lifestyle-concept) is that many people derive enormous satisfaction from being in a building whose components have an obvious link to the surrounding world. People are pleased to know that the earth walls encircling them were dug from the ground beneath their feet, that the straw keeping them so snug was grown a few fields away, or that the trees holding up the roof inside have descendents growing outside.
