Hempcrete vs. Concrete

In a society that is becoming increasingly concerned about how daily life impacts the environment, more and more industries are researching and adopting new and alternative methods to carry out their trade. The building and construction industry is one such sector, with many companies moving towards using sustainable and environmentally friendly materials to lessen their carbon footprint.

What is Hempcrete?

Hempcrete is a building material made from hemp, a plant from a strain of the Cannabis sativa plant species. To make hempcrete, the wooden core of the plant (called the shiv) is mixed with a lime binder and water.

It is a biocomposite material that is bound together when a chemical reaction occurs between the lime binder and the water. Void space is quite high in fully cured hempcrete as its lime binder is not designed to fill all the voids between the hemp.

What Are the Advantages of Hempcrete?

Hempcrete is an environmentally friendly building material that has an excellent ability to deal with humid conditions, and resist damp, fungus and mold due to the high pH of the lime binder. As it is made primarily from plant fibers, hempcrete is able to store a lot of moisture and release it when conditions are right.

Importantly, 325 kilograms of carbon dioxide are stored in one tonne of dried hemp, and hempcrete absorbs carbon dioxide not only when it is being grown, but after it has been made into building materials as well, greatly reducing its environmental impact through emissions and greenhouse gases. Additionally, hempcrete does not release any toxins into indoor environments, posing benefits for public health.

It is widely cited as being an excellent heat and noise insulator, with the thermal mass of the material allowing it to store heat and release it slowly as the building cools down, instead of trapping the heat inside the building through airtight construction. This offers financial benefits to homeowners that may not have to rely on heating and cooling systems so heavily.

Along with this, hempcrete is also cited as being good for supporting stud walls that may bend or buckle under supporting loads.

What Are the Disadvantages of Hempcrete?

Hempcrete, although environmentally friendly and superior as an insulation material, is highly variable in its formulations and ingredients. For instance,

Due to the high amount of void space in hempcrete, correct tamping is essential to achieve maximum integrity and bonding. The thermal performance of hempcrete is also largely dependent on the density of the final cured product, meaning greater control in this area needs to be exercized when compared to concrete.

What is Concrete?

Concrete is widely used in construction as it is inexpensive, quick to produce, and very durable. It is made from a mixture of aggregates, usually natural sand, gravel, and crushed rock. The aggregate is can be bound with lime-based cement or hydraulic cements including calcium aluminate cement, and water.

What Are the Advantages of Concrete?

Concrete an incredibly strong material with excellent abilities to resist compression, wind, water, and fire. It also increases the energy efficiency in buildings due to its ability to retain heat. It is also an effective sound-proofer.

It is easily moulded into any shape necessary for construction. It is also easy to repair as concrete can be sprayed into cracks or other sites of damage very easily. Spraying concrete can also allow it to be used in difficult to reach locations, such as on the inside of tunnels.

Concrete can be recycled and used as granular fill, and less and less waste or discarded concrete is being shipped to landfills.

What Are the Disadvantages of Concrete?

Although a very strong material overall, concrete can be damaged through exposure to water and freezing temperatures, possibly resulting in cracking.

Concrete is also a porous material meaning that it can be susceptible to mold. Unlike hempcrete, which stores and releases moisture according to the conditions of the environment around it, concrete expands and contracts with the environment as moisture and temperature changes occur. Again, this can result in cracks and loss of structural integrity.

As hempcrete is not suitable for use in load-bearing structures, concrete can also be too heavy to be used in some situations. Additionally, concrete needs to be reinforced to avoid cracking due to its low tensile strength.

Producing concrete has a more negative effect on the environment when compared to hempcrete. When creating the cement needed to bind concrete, large amounts of carbon dioxide are released into the atmosphere, with one tonne of cement releasing one tonne of carbon dioxide. Concrete dust can also contribute to air pollution, and those working regularly with concrete are at a risk of developing silicosis, an occupational respiratory disease.

Summary

Concrete holds a clear advantage over hempcrete in construction in that it can be used to build load-bearing structures. However, hempcrete has obvious advantages in its ability to resist mold, fungus, and damp, which are problems many homeowners face when living in older buildings, and can cause serious problems with respiratory health. Both concrete and hempcrete are resistant to fire, retain heat well, and act as effective sound-proofing materials. Any shift in industry between widespread adoption of concrete as a building material versus hempcrete will likely depend on the cost of the materials initially, and their suitability for varied, large-scale construction projects.

References and Further Reading

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