Hemp Insulation

Hemp is a very fine insulating material. This is a bold statement. So what qualities do you look for in an insulating material and how does hemp compare?

The Cost of Hemp Insulation

I have recently been quoted under €27 per square metre for hemp roof insulation and under €19 per square metre for hemp wall insulation. Cork by comparison was under €39 and  €27 respectively. This excluded transport costs which were clearly negotiable against quantity.

It comes in panels of 1000mm by 500 mm. The roof insulation panels are 200 mm thick and the wall panels are 140 mm thick.

So hemp insulation is a lot cheaper than cork and is generally very reasonably priced.

Thermal Properties of Hemp Insulation

Hemp has excellent thermal properties. To give you a precise idea the table below compares the U value of hemp with some other materials. U-values gauge how well a material allows heat to pass through. The lower the U-value, the greater a product’s resistance to heat flow and the better its insulating value.

Material	U Value – W/mK
Copper (included here to give an idea of the range)	380
Plaster Board	0.180
Dry Straw Bales	0.080 – 0.100
Strawboard	0.098
Woodwool slab	0.082
Sawdust	0.051
Foamed Glass Insulation	0.036 – 0.046
Cork	0.043
Fibre-glass Insulation	0.040
IsoNat hemp/recycled cotton insulation	0.039
Hemp and recycled cotton insulation	0.039
Thermalfleece sheeps wool insulation	0.039
Warmcel 500 wall insulation	0.036
Mineral Wool Insulation	0.032
Rigid polystyrene insulation	0.029 – 0.036
Rigid polyurethane	0.022 – 0.028
Rigid phenolic foam insulation	0.021 – 0.024

The Embodied Energy of Hemp Insulation

This is a measure of the energy used to process and transport the material and will clearly vary on how efficiently the hemp is processed and how far away manufacturing is from the building site.

Hemp can be and is grown across a wide area geographically widely including the UK, France, and Spain. It is a natural material and by comparison to synthetic materials, such as mineral and glass wool, it is probably safe to say it beats them all on the embodied energy measure.

However the whole picture would include a measure of the amount of energy saved by a material throughout the lifetime of its use. Having said that the embodied energy of almost any insulation material is insignificant compared with the energy saved by it over the lifetime of the building.

The Raw Material, Toxicity and Recyclability of Hemp Insulation

Yes, the environment is more than just an energy issue. What could be more environmentally friendly than growing the insulation material free from pesticides and chemicals? There is no toxicity that I am aware of in its manufacture, processing or usage. Hemp is an organic material.

Other Hemp Facts

• One of the earliest plants to be husbanded by man, hemp has been described as having the highest green credentials of any crop. It produces a huge variety of materials (fibre, wood, seeds), has a wide climatic range and a broad scope of uses. It has a high biomass and is an ideal rotation crop. It naturally suppresses weeds and so reduces the need for chemical or other treatments.
• Hemp wood chips can be mixed with lime to make Hempcrete which has a wide range of applications for insulating roof spaces, beneath or between floors, to build walls or as an insulating undercoat.
• The Hemp plant comes from the same family as the Cannabis plant the only difference being the quantity of THC produced.
• Before the industrial revolution hemp was the main source of rope and was in much demand by the world’s navies.
• Hemp is now used in the automotive industry for interior panels where it has proved superior to synthetic materials. It is also used in the manufacture of prestige paper.

Check out the informative Wikipedia entry: http://en.wikipedia.org/wiki/Hemp

And Finally

As a final thought remember that the single most important factor in any insulating material is that it be installed properly.

This article was written by John Wolfendale a director of Eco Vida