Untitled - avniR

Congrès International sur l’Analyse du Cycle de Vie Lille, Novembre 2011
COMPARATIVE LCA FOR TWO NATURAL INSULATING MATERIALS ON A WALL
Jean-Luc Menet*, Etienne Bocquillon, Emilie Decosse
Université Lille Nord de France, ENSIAME, UVHC, 59313 Valenciennes Cedex
* jean-luc.menet@univ-valenciennes.fr
Introduction
As regards to thermal insulation, straw bundles and linseed panels seem to be ecological at first
sight. The advantage of these materials is that their farming does not require specific cultivation areas,
because they are made from agricultural wastes. Straw is in fact an excess production in conventional
farming, and the linseed panels manufacturing uses short fibers that cannot be transformed by textile
industry.
The aim of the present study is to quantify environmental impacts using an exhaustive Life Cycle
Assessment of these two ‘natural’ products integrated on a wall, relatively to the ISO 14040. The results
are compared to a conventional insulated wall
Goal and scope of the study
The final goal of the study is to compare two types of insulated walls the area of which is 15 m² (3
m high vs 5 m long), with a wood structure.
To be called “passive house”, the thermal transfer coefficient of each wall must not exceed 0.15
m 2 .K/W, which deals to a thermal resistance of about 6.5 W/m 2 .K for the wall. Thus the functional unit has
been chosen to be the insulation of a wall during 100 years with a thermal resistance of 6.5 W/m².K. The
keys parameters are the thickness of insulating materials which must be chosen to obtain the correct
thermal resistance, and their shelf life. For the calculation of the insulation, only the insulating material will
be considered.
In our study, the following steps of the life cycle are considered: raw material procurement and
manufacturing, the distribution, the consumer use, and the end of life (post-consumer use).
Presentation of the two natural insulating materials
1 Insulated wall with straw
There are many possibilities to use straw for insulating. We have chosen the GREB straw ball
building technique [1]. The wall is composed of three elements represented on Figure 1.
To build a wall of 3m high and 5m long using straw bundles, the following quantities of materials
must be used: 30 straw bundles, 4 beams of 5m long, 16 beams of 2.86 meters long, 40 brackets of 0.35m
long, 0.96 m 3 mortar, 240 steel nails, and 273 m string.
2 Insulated wall with linseed panels
A fast study of the thermal conductivity of linseed shows the for the linseed panels insulating wall,
the isolating material thickness must be around 21cm. A 20cm thickness is chosen because it can be
found for sell. The insulation is made using the elements shown on Figure 2.
Bracket
Beam
Straw bundles
Wood board
Linseed panels
OSB
Mortar
FIG. 1 – Structure for straw insulation
FIG.2 – Structure for linseed insulation
- 61 -