Video Source » Sustain and Build
Hemp is probably the most sustainable, eco-friendly and versatile material on the planet. Hemp is a natural fiber product of the Cannabis sativa plant and when processed, the possibilities of its use are vast. Hemp has been around for a while and has been used for centuries to manufacture rope, canvas, paper, and clothing. In the US for example, Americans were legally bound to grow hemp during the Colonial Era. Abraham lincoln is known to have been a devoted hemp smoker and even presidents Washington and Jefferson both grew hemp. (More on the amazing qualities of hemp here). There are literally countless hemp derived products on the market and even more eco-friendly applications in animal feedstock, reinforcement fibres for the automotive industry (BMW & Mercedes door lining panels), paper pulp, horse bedding and as a construction material (hemp shiv).
Can you use it as a building material?
You bet. Hemp is the strongest natural fibre known to man and is reputedly stronger, weight for weight, than steel. Hemp grows fast from seed to four meters high in just over fourteen weeks, and is virtually disease resistant. To top it all off, it can be used in rotation with other crops and helps improve the soil. In Europe, the woody core of the stem of the hemp plant (Hemp shiv) is processed and used to make a wide range of materials ready for application in buildings, from blocks to floor slabs and even insulation.
Hemp is a also renewable industrial crop (that can be grown and harvested in many climates around the world), so when implemented in construction it can capture CO2 within the fabric of the building. This means that whilst a typical brick house can be responsible for around 50 tonnes of CO2 emissions in its construction, the same house built using a Hemp derived product can be built for 30-40% less CO2 emissions; additionally it absorbs CO2 in its manufacture so it has a negative embodied CO2.
Just have a look at the huge ecological advantages:
- Grows quickly and grows BIG: the plant grows very quickly and can reach 3 meters in less than 3 months. (allowing in some case for multiple yearly crops and ideal for crop rotation)
- It can be grown organically: no agrichemicals are used in the growing of the crop
- It’s a mighty crop: it grows so fast that no other plant can compete - including weeds (no herbicides are required)Negative carbon footprint: it sequestrates significant quantities of carbon dioxide (growth of 1 Tonne of hemp shiv uses up nearly two Tonnes of CO2 )
- o% Crop wastage: 100% of the harvested plant is useful
What kind of hemp materials are available?
One of the most common Hemp construction products is Hemcrete. A type of hemp concrete, Hemcrete is a blend of hemp shiv (the woody core of the plant) and a special lime-based binder. Together these products form a bio-composite building material that can be used for the creation of buildings that have excellent thermal properties (ideal when you are trying to save money on heating and cooling bills!) offering healthy and cozy living/working environments. Hemcrete can be used to manufacture building blocks, floor screeds, insulation and more importantly, you can pour it like concrete to form the outer skin of buildings. But its better than concrete because the hemp composite actually forms a breathable insulated wall with great thermal mass properties which means it stays cool when its hot outside and it keeps you warm when the temperature drops. All without the need to incorporate breathing membranes, waterproof sheathing, wall ties or even insulation. The only drawback, if you can call it that, is that hemcrete is non structural. It needs structural support, but lucky for the planet, timber frames are an incredible choice of renewable material capable of supporting structures of up 14 storeys these days. A building made entirely of renewable materials which has walls that are thermally efficient and has captured CO2 within the same walls is a remarkable ‘green’ design principle that should really become common practice.
SO, WHY DON’T WE ALL BUILD WITH HEMP?
Here are some of the advantages of Hemcrete:
- Hemcrete is made from renewable (locally grown) hemp based materials
- Hemcrete is highly insulating resulting in thin walls with a very low U value
- Unlike other insulators Hemcrete also has thermal inertia which is similar to thermal mass so houses built from Hemp change temperature very slowly reducing heating loads significantly below lighter weight buildings with the same U value
- Hemcrete is vapour permeable and when used with lime based renders and plasters creates a breathable walling system for healthy living.With such amazing advantages, a Hemp building material would probably be the most eco-friendly in the world
Part 2 of the video “Building With Hemp”
