Civil Engineering Reference
In-Depth Information
Insulation made of polystyrene and polyurethane is usually delivered as a
readymade product from the factory; urea formaldehyde foam is sprayed in on
site. The latter emits a lot of fumes during the hardening phase, particularly
formaldehyde. Depending upon how the materials are built in, polystyrene can
emit extra monomers of styrene while polyurethane can release small amounts
of unreacted isocyanates and amines. Even if the level of emission per unit
weight for these products is relatively small, large quantities of the materials are
contained in buildings. There is also a great deal of uncertainty about how long
plastic insulation materials will last.
The re-use of plastic-based climatic products is not particularly appropriate
because of their short life span. Even the recycling of climatic plastic products is
not very practicable, as most of them are fixed to other materials. An exception
can occur in cases where pure insulating boards of expanded polystyrene (EPS)
have been used. However, many of the plastics can be transformed to energy by
burning them in special furnaces with smoke-cleaning systems. Ashes from the
furnaces and plastic waste which is not recycled must be disposed of safely to
prevent seepage into the ground water or soil.
Timber materials
Timber has many good climatic properties both in its natural form and when
reduced to fine particles. Log walls have covered all the climatic functions in
Scandinavian dwellings for hundreds of years. The narrow joints between the
logs are usually filled with moss. Timber is wind-proof, it is a good regulator of
moisture and it has a useful insulation value even if it does not quite achieve pre-
sent standards, which can be reached by adding a little extra insulation on the
outside.
When timber is reduced to smaller particles, it has insulating qualities.
Sawdust, shavings and woodwool are available from different types of timber
and in different sizes. These can be used directly as compressed loose fill. In
Sweden, Finland and inland Norway this was the most widespread form of insu-
lation in framed building up to the 1950s. Loose fill can also be made into sheets
by adding cement, magnesite or glue. It is possible to make insulation boards
bound by the glue from the wood itself, e.g. wood fibreboards.
Cellulose can be produced from wood pulp for use in corrugated insulation
board and paper to protect against damp and wind. Thermal insulation made of
loose fill cellulose was patented for the first time in England in 1893. This was
made of shredded recycled paper, preferably containing a fire retardant and
impregnated against moisture. This method is very widespread today; around
1980 this covered about 30 per cent of the insulation used in Canada. Even in
