Hempcrete Explained: Benefits, Cost, and How It’s Changing Green Building

Sustainability in construction has been on the rise for years, and alternative building materials are one of many methods builders have been using to build environmentally friendly homes. “Hempcrete” is one of those materials.

What is Hempcrete?

Hempcrete (or Hemplime), is a bio-composite material made of hemp hurds, lime, and other natural materials.

Hempcrete got its start in France in the 1990s, where it was used as a non-loadbearing filler and insulation for walls. Hempcrete can be applied in two ways: it can be sprayed or cast in forms onto the construction site, or stacked in prefabricated blocks, like regular masonry construction.

“It’s what’s called a ‘monolithic envelope’; the heat stays in in the cool weather and stays cool in the warm weather,” said Jean Lotus of Hemp Build Magazine.

What Makes Hempcrete Eco-Friendly?

Hempcrete is both eco-friendly to make and to use.

1. During growth, hemp absorbs carbon dioxide, making it a carbon negative material.

2. A hempcrete block will absorb carbon dioxide throughout its lifespan, reducing the home’s carbon footprint.

3. Hemp and lime make hempcrete biodegradable.

4. Hemp is easily and quickly grown, so it can be easily restored/replaced should the need arise.

“it’s really easy to recycle; you can break it down and reuse the leftovers,” Lotus said. “The idea is to avoid building with petroleum-based products like vinyl.”

The thermal properties of hempcrete make it an excellent insulator; it also excels at maintaining a constant internal temperature. Pockets of air in the material and thermal mass provided by the lime binding allow hempcrete to trap heat.

What are the Benefits of Hempcrete?

There are many benefits to hempcrete, but two major ones are:

1. It’s resistant to cracking and mold

2. It’s fire resistant

The low density of hempcrete makes it lightweight, flexible, and resistant to cracking and mold buildup. The lighter weight makes transportation easier and reduces the overall weight of the structure.

Hempcrete is also very fire-resistant. The lime binder used in the material help ventilate heat and produces little smoke when set on fire, and the material doesn’t fully ignite under sustained exposure, according to ScienceDirect.

It’s important to note that hempcrete is not a replacement for a like concrete. It lacks the sturdiness needed to be load-bearing, so it’s primarily used to surround structures made of timber, metal, or concrete as an insulator within walls.

“You’re getting rid of siding, insulation, drywall, and just putting in the hempcrete in the wall,” Lotus said.

Availability and Cost

Hempcrete is gaining popularity in the U.S., but it’s still not widely used. A general lack of knowledge about the material, its ongoing research and development, and the need for permits for use in residential buildings are hurdles that hempcrete is still overcoming.

Hempcrete isn’t exactly scarce, but it comes from companies that specialize in hemp-based building. Hemp companies like Hempitecture and Hemp Block USA sell blocks, panels, and the raw materials for casting on site.

“What we’re saying here in the States is that it can be used, it just needs a supply chain,” Lotus said.

Do You Need a Permit to Build with Hempcrete?

Short answer: No.

In 2018, the Farm Bill reclassified hemp and allowed for its growth for industrial purposes, and, in 2023, hempcrete specifically was included in the International Residential Code (IRC), allowing for its use as a filler and insulation in one-and-two family homes and townhomes.

According to these codes, you don’t need an extra permit or license to build with hempcrete.

“Right now, you don’t have to get any extra permits if you’re building a two-story home in a low seismic zone,” Lotus said.

While the name can cause it to be compared to concrete, hempcrete isn’t foundational, but it does provide better ventilation and a lower carbon footprint. In a world where sustainability is increasingly important, you might be seeing hempcrete more in the future.

To learn more about green building and new home construction, visit newhomesource.com/learn.