High and mighty: how hemp is revolutionising construction

Did you know that the concrete industry generates 2.8bn tonnes of CO2 each year? That’s more than most countries. On top of that, the power relied on by buildings and construction accounts for 38% of the global carbon dioxide emissions, making it one of the most unsustainable industries on the planet. 

But, what if there was an ancient super grain that could replace cement and overall make construction more sustainable long term? Well, there is, and it’s called hemp. 

A tale as old as time 

Hemp is an ancient grain that has been used since 8000 BC to make building material, pottery, and fabric all across the globe. With its roots being traced back to Northern China, the plant has been found in Britain for centuries with King Henry VII fining farmers who refused to grow the seed. It has been hailed during war efforts for its strength and is viewed as an essential fabric for its breathable flexible nature. 

So why isn’t it more widely used now? 

No difference, big consequences

Hemp is part of the Cannabis Savita family, the same plant family as marijuana, and despite it only having less than half of one percent of THC (in comparison to marijuana’s 20% - 90%) it was categorised as a US Schedule 1 substance until 2018 and required extensive licenses to grow. Making it inaccessible to many and allowing its competitor, concrete, to take hold of the industry. 

But this all changed with the 2018 United States Farm Bill which distinguished Hemp from Cannabis and allowed the agricultural growing of Hemp across the US. 

However, in the UK growing and using hemp is still a tricky business. Due to limitations on CBD products and its connotations with marijuana, farmers are unable to harvest the flowers and leaves of a hemp plant (which are coincidentally the most expensive parts as they are used to make CBD oil) and they still need an expensive license to grow it. Resulting in many farmers viewing the plant as not financially viable. 

However, things are starting to change. As more public figures speak out in favour of medicinal CBD and its cousin cannabis gets an increasingly better image, the use of Hemp is on the rise.  

So why should we use hemp in construction? 

Not only is Hemp quick to grow and is non-toxic to handle, but when mixed with a lime binder it creates Hempcrete, which is an amazing insulation material saving buildings up to 50% on electricity and gas when compared to its competitors.  

During its production, Hempcrete has the potential to reduce carbon emissions at each stage due to its ability to “lock up” carbon and reabsorb it over the course of its lifetime. One cubic meter of Hempcrete will sequester 110kg of carbon from the atmosphere, meaning a house built out of 50 cubic meters of hempcrete will lock up over 5.5 tonnes of carbon during the building's lifetime. 

Meaning it’s pretty sustainable when compared to the industry average concrete.  In fact, it’s not just concrete that harms our environment when constructing a building, cement also has a detrimental impact on our world. 

When creating cement from concrete, you need a “clinker” (typically a mixture of calcium carbonate, clay, and gypsum) which in order to work needs to be heated to at least 1,500 degrees before it breaks down. This process releases large amounts of CO2 into the atmosphere and despite the industry's best efforts can never truly be affordably carbon neutral. 

When compared to its concrete competitor, the benefits of using hemp are widespread and with the rise in global warming as well as supply chain disruptions many in the construction industry are looking to the plant to solve industry problems. 

But can it? We think it can. 

If you’re looking for extra information on how the NHS can create greener buildings, make sure to sign up for our World Green Building Week webinar!