Constructing with flax, reed, straw, algae, bamboo and elephant grass
written by Willem Böttger
Professor Biobased Building at the Centre of Expertise Biobased Economy
Centuries ago man lived a sober life, using energy sources such as wood and peat to heat their houses and animal oils to create light. The houses were made of stone, wood or loam and insulated with sod, straw and wool.
With the active extraction of coal and later of oil and gas, living conditions improved considerably. The cheap fossil energy sources also ensured that we developed special materials, such as mineral wool as an insulation material and carbon composites for strong and light structures. The downside is that the economic growth, based on the increasing use of fossil fuels, has become synonymous with global warming, depletion of scarce natural materials and increasing environmental pollution.
To combat climate change, buildings have become insulated, but with insulation materials that require much more energy to produce them, so that the climate is more affected instead of less. And due to insulation, the indoor climate in homes has become worse. And this bad indoor climate affects us more because we live much more indoors than in the old days.
Impact for the construction industry
If we want to design a construction product or an entire house, we are dealing with properties and preconditions from production, material, design and market. If we want to construct a bridge and we have only wood available, we will design a different bridge than if we have stones available. If we have wood but no saw, we will design a different bridge than if we have a saw. Material, production techniques and design influence each other, give each other degrees of freedom and limitations.
By working with biobased materials, the production techniques, design and the market can and must innovate. This means a broad-minded approach from the lectorate and close cooperation with other lectorate groups, universities of applied sciences and research universities.
Historically, an architect would draw a building and the contractor would seek the material to build it. As materials and the circular process are becoming more important, the roles of architects, contractors and producers are changing. They need to learn more from each other’s field of expertise in order to achieve optimum results. The teachers and students of HZ have to adopt to this changing role.
Choice of material
The lectorate focuses on local Zeeland and West Brabant raw materials:
- Bio-composites are made from natural fibres such as flax and hemp, combined with a (partially) organic resin. Together they form a strong, stiff and light construction material.
- During the growth of fungi on fibrous and nutritious residual materials from agriculture, a dense network of mycelium is formed. Depending on the type of mycelium, fibre and food and the pressure, the materials can be hard, but also rubbery.
- With hemp lime (hempcrete), a mixture of lime and the woody parts of the hemp stem (the shives), external walls, other walls and even roofs are insulated. Hemp lime has a moisture-regulating effect, creating a comfortable and healthy indoor climate.
- Flax, reed, straw, algae, bamboo and elephant grass are local, insulating, moisture-regulating and sustainable products, with their own market dynamics. The lectorate is investigating locally produced bamboo.
Circular biobased economy
To reverse the growth in the use of fossil fuels and scarce natural materials, climate change and environmental pollution (indoors and outdoors), the government has decided to develop a circular biobased economy up to the year 2050.
The Biobased Building lectorate was established in this context. The lectorate is part of the Centre of Expertise Biobased Economy, a collaboration between Avans University of Applied Sciences and HZ.