Agriculture Reference
In-Depth Information
17
Hemp and the
Laurent Arnaud,
1
Bernard Boyeux
2
and Yves Hustache
2
1
ENTPE, France;
2
Consultant, France
17.1 Introduction
This chapter will provide a description of
the raw plant material, as well as the perform-
ance results of the products it goes into mak-
ing. The applications found for those products
will be described, together with a brief note
about the economic and environmental bene-
fits associated with their use. Finally, ongoing
standardization work and current research pro-
grammes will also be discussed.
The idea of using plant materials in the con-
struction industry is not a recent one. It is still
not uncommon to find old walls coated with
lime in which hurds have been embedded. With
the arrival of new mouldable materials, how-
ever, these rendering (or plastering) techniques
have gradually fallen into disuse.
Recent developments in our approach to
the building of houses have prompted a revival
in the use of plant materials as constituents of
building materials. New perspectives have been
provided by technical innovations and the reali-
zation that such materials provide environmen-
tal benefits and increase market diversity.
Reference to the received wisdom we have
inherited from the tale of
The three little pigs
would seem to argue strongly against this trend and
[the tale denigrates] against the use of plant materi-
als, such as straw, in the construction industry.
It would be a great shame were this sub-
ject not to be studied further. Hemp, in particu-
lar, as well as hemp wool, hurds and hemp
concrete, have been shown to possess a
number of advantages that have led to their
gaining ground within the construction indus-
try. Numerous laboratory investigations and
field trials, both in new builds and renovation
projects, have been undertaken over the past
20 years. Today, there are in excess of 100
hemp-based products on the market.
17.2
Fibre or Hurds? Matching
Materials to End Uses
With the exception of hemp seed, which has
no significant use as a building material, hemp
can supply two co-products: (i) the bast fibres
and (ii) the woody core of the hemp stalk used
to produce hurds. These co-products possess
specific properties and are used to produce dif-
ferent construction materials (Fig. 17.1).
The fibres are used to produce insulating
material in which synthetic fibres are replaced
by hemp fibre. In addition to the environmen-
tal value of using plant matter, these materials
benefit from the mechanical strength of the
hemp fibres.
The employment of hurds in construction
makes use of two important characteristics of
these particles: their low density and their prop-
erties as an isolator that arise from this low
