Hempcrete: A Homeowner’s Guide to Sustainable Building

By: Matt MalkinJune 7, 2024

Imagine building your dream home with a material that's not only eco-friendly but also provides superior insulation, longevity, and comfort. Enter hempcrete, an amazing building material that’s making waves in sustainable construction. If you've never heard of hempcrete, you're in for a treat. This guide will introduce you to the benefits of using hempcrete for your new home or renovation/addition and why it’s worth considering.

What is Hempcrete?

Hempcrete is a natural building material made from the woody core of the hemp plant (called shiv or hurd) mixed with a lime-based binder. 

Despite its confusing name, hempcrete is not like concrete because it’s not a load-bearing material. With hempcrete, you still need to have wall framing.  Hempcrete is used between the framing and acts as the insulation and substrate.  The hempcrete material is then covered with plaster on the interior and exterior wall surfaces, and voila, you’re done.  

A typical wall assembly has many layers of materials that include plastics and other synthetic materials.  A hempcrete wall assembly removes the need for any synthetic materials, so you can have a wall that is entirely natural and healthy.

Hemcrete

Mock up of a hempcrete wall.

Why Choose Hempcrete for Your Home?

Eco-Friendly and Sustainable:

  • Renewable Resource: Hemp grows rapidly and requires minimal pesticides and herbicides, making it a sustainable choice.

  • Carbon Negative: Hemp plants absorb CO2 as they grow, and the lime binder captures more CO2 as it cures, making hempcrete carbon-negative over its lifecycle.

  • Hemp is a hardy plant, and can grow in many climates and soil conditions, making it available regionally, which cuts down on transportation emissions.  Its hardiness also makes it a great rotator crop for regenerative farming.

Energy Efficiency and Comfort:

  • Superior Insulation: Hempcrete’s excellent thermal properties keep your home warm in the winter and cool in the summer, reducing energy bills.

  • Thermal Mass: A hempcrete wall is really thick - about 10” depending on your climate.  Its thickness helps absorb heat during the day, then release it into your home at night.  This keeps your home at a consistent, comfortable temperature without the need for mechanical heating or cooling.

  • Controls moisture in the most amazing way: If you live in a humid climate, this material will make you cry with joy. It wicks moisture out of the air and moves it to drier air. So if it’s humid inside the house, it’ll pull it out to the outside. It can also store moisture without leading to mold (similar to sheep’s wool).

Healthy Living Environment:

  • Breathable Material: Hempcrete allows moisture to pass through, preventing mold and mildew and contributing to better indoor air quality.

  • Non-Toxic: Unlike some traditional building materials, hempcrete doesn't release harmful chemicals or toxins, making it a healthier choice for you and your family.  It replaces the need for many petroleum-based products.

Durability and Longevity:

  • Pest Resistant: Hempcrete is naturally resistant to pests, including termites.

  • Fire Resistant: The material is highly fire-resistant, providing an added layer of safety for your home.

  • Low Maintenance: Hempcrete structures are long-lasting and require minimal maintenance, reducing long-term costs.

Hempcrete being mixed

Hemp getting mixed with the lime. Water hasn't been added yet.

How Hempcrete is Used in Construction

Hempcrete is essentially an insulation material.  You still need floor, wall and roof framing since it’s not a structural material.  

It is most commonly used as the wall insulation, but you can use it as floor and roof insulation.  However, it tends to be pretty cost prohibitive for floor and roof insulation, so it’s usually better to use a natural batt or blown-in insulation material (such as wood fiber, sheep’s wool, or hemp batts) for roof and floor insulation.

Hempcrete is amazing for a wall assembly because the entire wall can be made up of natural materials. 

  •  In a traditional wall assembly, you have many layers of synthetic materials, starting with the drywall on the interior side of the wall, then a plastic vapor retarder, then some (usually) synthetic insulation between the wall studs, then a chemical-infused plywood substrate, then a petroleum-based house wrap, then a potentially synthetic exterior siding material.  

  • In contrast, a hempcrete wall is hempcrete and plaster.  The plaster can be the interior and exterior finish of the wall.

Hempcrete Homes

A hempcrete house can look like anything you want!  But like any other method of construction, the simpler the design, the easier and more affordable it will be to build.

Here are a few examples of hempcrete homes built in the US.

Goshen Hemp House - Goshen, MA:

Hempcrete walls before plaster is installed.  (Goshen Hemp House design and construction by Village Carpentry, hempcrete install by HempStone LLC.)

Work-in-progress shot of the lime plaster exterior.  (Goshen Hemp House design and construction by Village Carpentry, hempcrete install by HempStone LLC.)

Cape Code Hemp House - Cade Code, MA:

This house was finished in cedar exterior cladding over the hempcrete walls. (Architect: Estes Twombly and Titrington Architects, Hempcrete contractor: HempStone

Framing of the Cape Code House before hempcrete install. (Architect: Estes Twombly and Titrington Architects, Hempcrete contractor: HempStone

Push House - Asheville, NC:

The first hempcrete house built in the US.  (Push Design)

Wally Farms - NY:

Farm worker cabin (Design: Kaja Kuhl, Hempcrete Contractor: Hempstone)

What to Consider When Building with Hempcrete

  • Initial Costs: While hempcrete can be more expensive initially due to limited availability and production scale, the long-term savings on energy and maintenance often offset these costs

  • Construction Time: Hempcrete requires a longer curing time compared to traditional concrete, which might extend your building schedule. However, the long-term benefits often outweigh this initial inconvenience.

  • Availability of Expertise: Since hempcrete is still relatively new in many regions, finding builders and contractors experienced with the material might be a bit more challenging. Look for professionals who have experience with sustainable building practices.

Final Thoughts

Building with hempcrete offers a unique opportunity to create a home that is not only environmentally friendly but also beautiful, comfortable, durable, and healthy. While the initial costs and construction time might be higher, the long-term benefits make it a worthwhile investment. If you’re passionate about sustainability and looking for innovative ways to reduce your environmental footprint, hempcrete could be the perfect material for your new home or addition. 

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