How Are Hemp Concrete Blocks So Lightweight?

Lightweight, strong, durable, sustainable, and non-toxic. Could there be a better way to describe a building material? Hemp concrete blocks have continuously gained popularity as reliable building materials as they’re more durable than standard concrete, despite weighing 6-8 times less.

With the increasing concerns about global warming and its negative effects, homeowners and the construction industry are beginning to embrace sustainable building alternatives – and hempcrete stands out as an eco-friendly solution.

So, what makes this construction material so strong yet so light? How is hempcrete made? What are the benefits of its lightweight nature?

What Makes Hemp Concrete Blocks Lightweight?

To manufacture hempcrete, hemp hurd is mixed with water and lime which acts as a natural binder. Among all-natural fibers, hemp has the unique capability to bind well with lime thanks to its shiv (inner woody core) that boasts high silica levels. Fully cured hempcrete blocks weigh about one-sixth of the standard weight of concrete blocks.

Here’s a step-by-step overview of the hempcrete production process:


Controlled proportions of hemp hurds, water, and lime-based binder are mixed together. Lime is used as the binder because it doesn’t affect the hemp’s absorption properties as well as facilitates temperature regulation. Some varieties of lime-based binders such as hydraulic lime, tend to speed up the hardening process for hemp concrete while maintaining the water vapor diffusion rates.

While hempcrete is generally lightweight, the density may vary from brand to brand. The mixing process determines the density of the by-product.  Typical hempcrete densities range from 440-550lbs/cubic-meter, however, the density can be amped up to 1300-2200lbs/cubic-meter by using a higher binder content. Heavier hempcrete blocks have better mechanical strength and recommended for large buildings.

Hemp has a highly porous internal particle structure of up to 70%. Depending on the region’s climate conditions, hempcrete manufacturers manipulate this degree of porosity for better functionality. In colder regions, higher porosity is desirable for better heat retention. In warmer climates, higher density and less porosity are recommended to avert overheating.


The molding stage involves pouring the hempcrete mixture into a special press that shapes it into blocks of different sizes. You can mold the hempcrete to any shape that’s suitable for your particular construction project.

Open-Air Curing

This stage involves drying out the hemp concrete blocks in the open air to strengthen and harden them. The curing process can range anywhere between 6-10 weeks, depending on the weather conditions in your area and how wide you want your blocks.

What Are the Benefits of Using Lightweight Hempcrete?

The lightweight nature of hemp concrete blocks comes with a lot of benefits, including:

Reduced Construction Costs

Unlike regular concrete bricks that are heavy and costly to buy and transport, hemp concrete is lightweight, making it relatively cheaper to transport. This will be quite beneficial to low- to mid-income earners looking to build their dream homes.

Enhanced Sustainability

Hempcrete’s lightweight production allows for reduced embodied energy. In comparison, the manufacture of concrete blocks is intensive and consumes a lot of energy. As a result, it releases a lot of carbon dioxide into the atmosphere which increases the greenhouse effect.

Saves on Energy Costs

Hempcrete is a good thermal regulator – it diffuses accumulated heat during hot days to prevent overheating, and retains it when temperatures drop. This allows you to save on overall heating and cooling costs at your home. Your HVAC system also doesn’t overwork, increasing its useful life and reducing repair costs.

Eliminates Structural Overloading

For remodeling projects, it’s important to maintain the structural integrity of your building even after taking down walls. The low density of hempcrete makes it a suitable construction material for remodeling and repairing buildings whose structural integrity has already been compromised.

Easy Site Maintenance and Enhanced Site Safety

Using concrete increases the risk of injuries at construction sites. From falling blocks to inhaling cement dust, the risks are limitless. However, your construction site can be safer by utilizing the lightweight structural hempcrete blocks. It’ll also eliminate the need for heavy machinery to carry the concrete blocks and make the after-construction clean-up easier.

Faster Construction Process

Being lightweight and easy to use, hempcrete can accelerate the construction process. This is especially important for urgent construction projects that have a timeline of a few weeks or days.

Hempcrete: A Lightweight Building Material with Durable Results

The society is increasingly embracing new ways to conserve the environment. The construction industry isn’t left behind as many companies make moves toward using environmentally friendly materials like hempcrete to lessen their carbon footprints.

You can enjoy the benefits of this biocomposite by making your next construction project a hempcrete project. Besides being lightweight, hempcrete is resistant to fire, mold, and pests. It can also adequately absorb moisture to keep your indoor humidity levels at bay.

Today, one of the main problems with hempcrete is its poor accessibility due to limited production. However, the production and use of hempcrete is expected to increase in the next years, especially after the legalization of hemp cultivation in the country.

Check out our other posts for more information on hempcrete.