Hemp Lime Composite as a Natural Building Material for Proposed Walls in Irish Construction
Jack Fleming,
Atlantic Technological University

We live in a world that is increasingly conscious of the need to reduce our reliance on fossil fuels and limit carbon dioxide emissions into the atmosphere. The construction and built environment sectors account for around 37% of Ireland’s carbon emissions, equaling that of agriculture. This 37% of emissions is made up of approximately 23% operational emissions associated with the energy we use to heat, cool and light our buildings. The further 14% of the emissions consist of embodied carbon emissions from the production and transport of construction materials, the constructions process itself, and the maintenance, repair and disposal of buildings and infrastructure.

Clearly, there is a pressing need to transition to building techniques and materials that emit less carbon dioxide during their manufacturing process and use. There is a need for truly sustainable insulation materials; ones that are produced locally to where they are used, use renewable raw materials and use the least amount of energy in their production and utilisation. Hemp lime composite (hempcrete) is one such material. A combination of the chopped stalk of the hemp plant, and a lime-based binder, hemp lime composite provides a healthy, sustainable, natural, low embodied energy building material that can truly claim to be better than zero carbon.

Architectural Technology is the application of science and technology to the art of designing and constructing buildings. It encompasses a range of tools, techniques, and methodologies that enhance the efficiency, sustainability, and functionality of architectural projects. In this report Architectural Technology was employed by analysing the characteristics on a hemp lime composite mixture in a hope to further understand this unique natural building material. Some of the main features of interest when writing this report included the sustainability and environmental benefits associated with the material, the health benefits that are introduced when buildings are constructed with the material, the plants farming potential and ease of production, and lastly the economic efficiency that the material can provide.

Sustainability and environmental benefits - hemp lime composite is a renewable, environmentally friendly building material with a high capacity for carbon sequestration. One hectare of hemp sequesters 9 to 15 tonnes of carbon dioxide, similar to the amount sequestered by a young forest, but it only takes five months to grow. Hemp lime composite offers a sustainable and environmentally friendly alternative to traditional construction materials. Its low carbon footprint, renewable nature, energy efficiency, and biodegradability make it a valuable choice for green building practices and contribute to reducing the construction industry’s overall environmental impact.

Health benefits - lately there has been a resurgence of interest in older, more natural building materials and methods as a result of our growing awareness of the risks associated with an overreliance on fossil fuels and our increasing understanding of the detrimental side effects of synthetic building materials mass produced by highly industrialized processes. Using hemp lime composite as a building material promotes indoor air quality, reduces exposure to toxic substances, enhances thermal and acoustic comfort, and contributes to a more sustainable and eco-friendly living environment, ultimately benefiting the health and well-being of building occupants reducing the risks of Sick Building Syndrome (SBS).

Farming - The Irish climate and soil have proven to be ideal for hemp growth and production. It breaks the cycle of disease when used in crop rotation, it prevents soil erosion, and it requires low or no use of pesticides. Its low environmental impact and diverse uses make it an attractive option for farmers looking to make a positive impact on both their farms and the broader agricultural and industrial sectors. To encourage more widespread development, existing regulations and legislation must be amended and better payment schemes must be offered.

Economic efficiency - Hemp can be grown in diverse locations with few resources. It provides a more cost-efficient alternative for construction. The introduction of widescale local growth would provide widescale local benefits. Hemp lime composite offers economic benefits through cost-effective production, energy efficiency, reduced carbon emissions, and long-term savings in construction and maintenance. Additionally, its versatility and compatibility with sustainability incentives make it an attractive choice in the evolving construction industry.

The report investigates the hemp lime composite material through both primary and secondary research. Material from both internet and book research has been used in the secondary research, which has been done utilising a mixed media strategy, identifying the technical design report’s objectives. An extensive analysis of literature from academic and governmental sources, including peer-reviewed studies, and international and European standards. Primary research was conducted at Atlantic Technological University (ATU) Galway, Dublin Road campus under the supervision and guidance of lecturers and technicians. All tests were conducted in the ATU concrete laboratory using standardised methods and equipment where possible. The following tests were conducted:

Elemental analysis - the primary research includes an analysis of hemp shiv and prompt natural cement. It highlights the characteristics of hemp shiv, such as its elasticity and compressibility, and the properties of prompt natural cement.

Hygroscopicity testing - this test measures the water absorption capacity of hemp shiv, demonstrating its porosity and potential for thermal insulation due to its high absorption.

Slump test - evaluate the workability of the mixture.

Rate of evaporation test - the report discusses the time it takes for hempcrete to reach stable weight and the recommended drying period for applying finishes to hempcrete walls.

Cylinder break test - evaluate the compressive strength of the mixture after it has reached a dry state, revealing its lightweight nature compared to conventional concrete.

Thermal analysis - the report includes thermal analysis results comparing hemp lime composite to a sand-cement mixture. It highlights hempcrete’s heat absorbing and heat retaining properties.

In conclusion, Architectural Technology is at the forefront of modern architectural and construction practices, offering innovative solutions to design challenges while promoting sustainability and efficiency. Despite limitations, the report anticipates hemp lime composite becoming a significant part of the Irish construction market, particularly for proposed walls, due to its eco-friendly nature and potential for locally sourced materials. Hemp lime composite has the potential to reshape the built environment of today and tomorrow.


Judges' comments

While exploring a material very local to Jack’s location of study, Judges felt that he has highlighted an important traditional construction method that is important for the modern Architectural Technology professional concerned with the sustainable credentials of their projects. Providing a thorough background to this traditional material, the work highlights the renewed importance it could make in modern construction.

The Judges liked this project for the ample evidence of the practical approach to and depth of research and reading contributing to this work. They particularly liked the thorough approach to his testing. A well-documented and clear methodology with well documented and clearly explained results.

Judges were very complimentary about Jack’s approach to the work and would like to congratulate him on being very clear in his writing style and inciteful, clear and to the point in his conclusions. The work is aspirational in its conclusions in highlighting a low-tech solution that can use locally sourced materials to provide an environmentally sustainable construction product in an industry that often looks to high tech solutions to create more sustainable buildings.

It was agreed that the research discussion was built from very strong knowledge foundations, with appropriate background research, excellent literature review and use of robust testing methodologies. Jack’s report will be of significance to anyone within the Architectural Technology discipline.