Agriculture Reference
In-Depth Information
Use in construction
Shives
Fibres
Underfloor
Insulation
Concrete
Insulation wool
Fig. 17.1.
From plant to building - hemp in the construction industry.
mass:volume ratio. Other properties, including
their elasticity and permeability, are also appre-
ciated in the construction industry. Today, par-
ticles of hurds are used primarily to produce
light and superlight concretes and mortars,
whose properties are very much linked to their
composition. By varying the amount of binder,
materials can be produced that have very differ-
ent end uses, including roof insulation, paving,
wall construction and rendering.
Hurds can also be used as a space-
occupying insulating agent that can be poured/
packed into cavities and under floors. These
uses have not been developed fully due to a
lack of production.
The mattress is produced by a mechanical
or pneumatic carding process and is then
passed between two rollers and into an oven.
The temperature and length of the oven, as
well as the speed at which the mattress
progresses, allows the fusion of the external
part of the heat-fusible fibres (consisting of two
fibre components) on to the hemp fibres, with-
out the hemp fibres themselves being affected
by the high temperatures. The space between
the two rollers in the oven dictates the final
thickness of the insulating wool produced.
On exiting the oven, the wool is cut and
conditioned. The lightest wool is usually rolled
and, in some cases, compacted in order to
minimize transport, handling and storage costs.
The denser wool (semi-rigid panels) is cut up
into small panels (generally 0.6-1.2 m) and
packaged.
17.3 Hemp Wool
17.3.1
Mode of production
17.3.2 Performance
The first hemp wool products - and flax wool
products - appeared in 1998. Since this date,
the design of this material and all other similar
woollen fibres has remained the same. The
production involves the joining together of
hemp fibres using heat-fusible fibres, generally
of polyester. The process demands a uniform
mix of the two fibre types. This is used to make
a well-aerated mattress. The uniformity of the
mix is essential to the reliability of the end
product, as it influences the proportion of heat-
fusible fibres.
The wool fibre produced is, in reality, very
similar to the insulating synthetic wool com-
monly available today and is used in the same
way. The resulting insulation is due to the very
low density of this material (30-100 kg/m
3
)
and the amount of air trapped in the fibres.
The trapped air has a very low thermal conduc-
tivity and it is this that confers upon the fibres
their excellent insulating properties, providing
it remains immobile and is not compressed.
