Natural Building Materials – Hempcrete a Major Contender in the Race to Replace Concrete.
The Concrete Conundrum
Concrete is the most widely used artificial material in the world. Valued for its versatility, durability and ease of production, its first uses can be traced back to ancient Greece c.1400 BC. Concrete has been used in many of the most famous structures ever built. It is arguably one of the most influential materials in human history, with over 7 billion cubic meters of concrete laid each year.
However, the story of concrete is not all positive. Cement, the essential binding agent in traditional concrete, causes severely harmful environmental impacts at all stages of the production process. From airborne pollution generated by machinery during quarrying to large quantities of CO2 emissions released in the heating process. If the Cement industry were a country, it would be ranked as the 3rd highest producer of CO2 emissions in the world, 2nd only to China and the USA. A Chatham House study from 2021 estimated that cement production accounted for 8% of global CO2 emissions.
These figures are not expected to drop. Over 4.4 billion tonnes of cement are produced annually with a projected rise to 5.5 billion by 2050 to cater to the rising demands of rapid urbanisation. Given the state of global ecology and the failing targets set by the Paris Agreement, the construction industry is faced with the need to re-invent its most common material rapidly.
What is the Solution to our Concrete Dependency?
Fortunately, perspectives are changing and the demands for sustainable materials are growing as the construction industry seeks to decarbonise.
However, simply replacing concrete is not an easy task. Its strength and resilience qualities are nearly unparalleled and it is an economically viable option for many construction projects around the globe. Considering this, many new materials are being developed to replace concrete sustainably with substitutes using recycled waste, bamboo and hemp being some of the most notable re-inventions.
The Practical and Environmental Benefits of Hempcrete
One of the most popular emerging concrete substitutes is Hempcrete. It is a biocomposite material made from a mixture of hemp, lime-based binder, water and sometimes sand or pozzolans. It is marketed under names like Hempcrete, Canobiote, Canosmose, Isochanvre and IsoHemp.
Hempcrete has several practical benefits:
- It is lightweight and has a high thermal mass, making it an excellent insulator and an ideal substitute for other types of more carbon-intensive materials such as fibreglass or foamboard.
- It is significantly less brittle than traditional concrete and handles a greater degree of movement. As a result, it does not require expansion joints to withstand contraction or expansion.
- Fire retardant.
- Like traditional concrete, it has exceptional longevity and can last hundreds of years.
- Hempcrete provides high vapour permeability allowing for improved temperature control in indoor environments.
- It also has a lower mould risk and due to the natural fungal resistance of hemp, mould will not feed on the material itself.
The environmental benefits of Hempcrete are well known at this point. The European Commission for Agriculture and rural development strongly supports hemp production as it contributes to European green deal objectives.
- 1 Hectare of hemp sequesters 9-15 tonnes of CO2.
- The plant itself is very robust and not susceptible to pests; in most cases, the use of insecticides, herbicides or fungicides is unnecessary.
- Dense leaf coverage provides natural soil cover and helps prevent soil erosion.
- Hemp supports biodiversity. The timing of its natural flowering cycle coincides with periods of typically low pollen production from other plants. Hemp produces high levels of pollen as well as shelter for birds and seeds for the consumption of other animals.
- Hempcrete is a carbon sink; it continues absorbing carbon throughout its lifetime.
Not Quite the Perfect Substitute
Unfortunately, Hempcrete is not the one-size-fits-all solution to replace concrete. The materials differ in many ways. Notably, hempcrete does not have the mechanical ability that traditional concrete has and suffers under high levels of moisture absorption.
Hempcrete cannot be used as a load-bearing component in structures by itself and must be reinforced using other materials such as wood or stone.
When using hempcrete walls, joints between the ground and material must be added to prevent rising capillary water from saturating the walls.
When used externally, hempcrete walls are also susceptible to degradation from long-term exposure to rain (noticeable deformation may occur at over 60% moisture content).
These limitations are nonetheless easily worked with. Appropriate knowledge of hempcrete’s applications and proper construction techniques enables safe and effective use, as has been demonstrated by many successful projects e.g. Phoenix Lewes, Flat house and Clay Fields.
It is unlikely that any single material will fulfil the role that concrete has played in construction. At least in the imminent future, sustainably replacing concrete will likely be achieved through using a variety of sustainable alternatives such as hempcrete.
The Rise of Hempcrete
The current prospects for this material are positive. Regulations that have previously hampered hempcrete production are evolving and public awareness of the material is rising.
Hempcrete was recently approved by the US residential building code in 2022 and will be available for use in commercial projects in 2025. The growing popularity and deregulation of hemp are creating a widespread increase in applications of the material.
According to DATAINTELO market research, the projected compound annual growth rate of the Hemp concrete industry for 2021-2030 is 10.3%.
France is one of the world’s leading producers of hempcrete and is demonstrating its potential through a number of projects. In Paris, a seven-story block of social housing was built using a mixture of hempcrete and wood for the facade.
Designed by architecture firm Barrault Pressacco and located in the 18th arrondissement, the innovative and stylish structure displays the possibilities of hempcrete in affordable housing.
With the french government legislation that will require all new public buildings to use at least 50% natural materials starting in 2024, this housing project is certainly not the last social housing structure that will use hempcrete.
The deregulation of the hemp plant, approval of hempcrete by building standards and continuing successful applications in construction projects shows a promising future for the material. Its undeniable environmental benefits and growing awareness in the construction industry will help scale up hempcrete production, which will invariably facilitate its use in future sustainable building projects.
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The Firstplanit database is continually expanding to feature a growing number of sustainable building materials. The data points for these products are collated and validated by the Firstplanit team creating the most in-depth product evaluations available. View our listing for IsoHemp a Hempcrete Block to develop a holistic understanding of the products impacts.