Agriculture Reference
In-Depth Information
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It may be used in loft spaces and loft
can be substituted for other reported insulating
materials. Whether they be alveolar or fibrous
in construction, they all function on essentially
the same principles. They also present environ-
mental advantages - advantages that require
confirmation - and benefit from the 'asbestos
factor', which has shaken confidence in the
safety of conventional insulating materials.
These advantages provide new opportunities
that may be realized if the industry can show
itself to be economically competitive relative to
the products it wishes to replace - products
whose cost has been particularly low. In order
to meet these requirements, the industry can
become more efficient in a number of areas:
production, automation, compression and con-
ditioning capacity, and the mixing with other
natural fibres, which may introduce comple-
mentary characteristics.
Finally, a process that uses a plant-
based binding agent, rather than a synthetic
one, will result in a product that meets the
expectations of consumers better and is
more in line with environmentally friendly
objectives.
conversions.
On a traditional wooden frame, hemp
wool is placed in two layers below the exter-
nal covering. The first layer is introduced bet-
ween the rafters; the second layer is placed
over the rafters to insulate them. This second
layer may be placed on or between the roofing
battens that support the external covering.
In truss roofs, hemp wool is installed
in one or two layers. The first layer is
placed between the trusses and the second
is applied to the roof battens that support
the roofing material.
In all cases, it is important that ventila-
tion be provided between the hemp wool
and the outer shell of the roof and that the
joints and extremities are weatherproofed.
Pitched roofs for loft conversions
must be equipped with an outer covering,
but these may have limited permeability to
water vapour. Where this is the case, a
protective membrane must be placed
between the hemp wool and the facing.
Use in wall construction (both solid and
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partition walls).
Hemp wool can be used in the form
of semi-rigid panels:
- between the frame of the wall, where
the frame is made of wood;
- in cavity walls or on a metal frame, in the case
of walls made of bricks or breeze blocks.
17.4
Hemp Mortars and Cement
17.4.1 Introduction
To our knowledge, hurds were first used as an
aggregate for the production of light cement
in 1986 by Charles Rasetti in collaboration
with
Chanvrière de l'Aube
in order to reno-
vate the
Maison de la Turque
at Nogent sur
Seine, France. Contrary to popular belief, this
is not an ancient/traditional technique and has
been developed at all levels by French
pioneers.
Certain well-informed professionals
quickly recognized the technical potential of
these concretes. They were confronted by a
major difficulty, however: the significant cap-
acity of hurds to absorb water, which competed
with the binding agents' need for water. This
could result in the mixture failing to set and the
associated consequences. After exploring a
number of avenues - waterproofing, various
treatments, water saturation - the need to
focus on the make-up of the binding agent(s)
17.3.4 Regulatory aspects
Hemp wool is an industrial product and is
therefore subject to a number of national and
European technical regulations.
Today, certain hemp wool products avail-
able on the market have been approved offi-
cially for use in roof construction.
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For all other uses, the manufacturer should
be approached for advice and their recommenda-
tions followed with regard to installation and use.
17.3.5 Conclusions
Hemp wool products, as well as other natural
materials such as flax, sheep's wool and feathers,
