A-Z of Self Build Guides Materials Sourcebook: Hemp

Date Published:

02/06/2008

Self builders are getting very excited about hemp. It's natural, renewable, and is an excellent insulator, but used to be known for its narcotic rather than its constructive properties.

By Andrea Dean

In France, it's been widely used in buildings for years, but across the Channel we're only just beginning to realise what an eco-friendly, versatile material hemp is.

What is Hemp?

Hemp is a fast-growing plant with two constituent parts - fibre and a woody core, also known as the shiv or hurd. The strong fibre is used for insulation, or can be made into fabric, floorcoverings, paper or rope, and the shiv is used in construction materials. Although hemp is from the same plant species as marijuana, industrial hemp doesn't contain the same chemicals and so is ineffective as a drug.

Centre for Alternative Technology

Why is it so Eco-Friendly?

Where do we start? Hemp grows far more quickly and densely than trees - it can be harvested just 120 days after planting, whereas trees take at least five years to produce paper or pulp. It requires far less fertilizer, water and pesticides than cotton, and over 99 per cent of the plant can be used. While growing, it stores carbon from the atmosphere and overall the CO2 balance of the hemp crop means that CO2 may actually be removed from the atmosphere and locked away into the fabric of that buildings that are constructed from it.

There are much lower emissions of CO2 from the manufacture and curing of lime (to mix with the hemp) than with Portland cement, a component of concrete. Hemp used for construction has great thermal capacity and, applied appropriately, will reduce overheating in summer and retain heat in buildings longer in winter.

And, when you need to dispose of hemp products they can be ploughed back into the soil without harming the environment.