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November 14, 2017

Could Hempcrete be the next big sustainable building material?

Industrial hemp is a variety of the Cannabis Sativa plant, but unlike its marijuana relative, hemp has long been valued for its fiber content, strength and versatility – features that have caught the attention of builders, architects and manufacturers worldwide.

In 2010, North Carolina-based architecture practice Push Design brought to life a ‘breathable’ home prototype whose exterior walls are made of 12-inch-thick Hempcrete. Hempcrete is an eco-friendly compound of industrial hemp, hydraulic lime and water that has an insulating value of R2.5 per inch.

The material sequesters carbon from the atmosphere, and undergoes a natural petrification process as air filters through it. This means it actually becomes stronger over time.

Another example of an alternative housing solution using hemp that has grabbed headlines is Hemp Home: Tiny+ by award-winning New York architect and Passive House consultant, Christina Griffin, who worked with GreenBuilt for the project.

Designed to be the first modular HempHome to reach Passive House standards, and be certified Net Zero by the Living Building Challenge, the project will feature Hempcrete walls that modulate humidity, eliminate the building’s carbon footprint, and have an R-30 insulation.

“Hempcrete materials provide many advantages over other insulation and wall envelope assemblies,” Hemp Home’s project team explains on their Kickstarter page.

“Hempcrete walls are simpler than most conventional wall systems. They don’t need a vapour barrier, additional sheathing, rain screens or complicated engineering to prevent moisture buildup in the walls. Vapour permeable, i.e. breathable hempcrete walls regulate indoor humidity. They allow moisture to pass through the wall instead of getting trapped in the wall cavity.

“Yet they are airtight and provide good thermal insulation. The lime binder provides fire and [mould] resistance, repels pests, and makes the composite extremely durable. Hempcrete provides good racking resistance and becomes structurally stronger over time. It does not deform or crumble and so does not slump or create air gaps in the walls.”

As a prefab modular home, Hemp Homes can be easily customised – whether homeowners are looking to add a bedroom for a child, set up a home office, or seeking to live “off the grid”.

The team is also developing a prefab hemp-lime panel technology that will enable future Hemp Homes to be built efficiently and inexpensively. Currently, Hemp construction is expected to cost about seven to ten percent more than traditional methods. However, as with many other ‘fringe’ sustainable innovations and applications, this higher up-front cost evens out over the lifespan of the building.

Keep reading on