Civil Engineering Reference
In-Depth Information
Both types of mineral wool, especially rockwool, have aliphatic mineral oils
added up to about 1 per cent by weight to reduce the dust. An emulsifier is often
added in the form of a synthetic soap, for e.g. polyethoxylene, up to 0.2 per cent
by weight, and a foam reducer, usually polymethylsiloxanol, up to 0.5 per cent
by weight. Both glasswool and rockwool are usually made as matting, but both
types are delivered as loose wool. Mineral wool products are light and have
extremely good thermal insulation values.
When used as insulation both glass and rockwool need a vapour barrier of alu-
minium or plastic sheeting, partly to avoid dust and partly because the material
cannot regulate moisture particularly well. Research has shown that in timber
frame buildings, rockwool, and to a certain extent glasswool, increase rot and
damage caused by damp on the timber framework, unlike the more hygroscop-
ic insulating materials such as cellulose fibre (Paajanen, 1994).
Mineral wool products can also be criticized for other reasons. Many experi-
ments indicate a connection between exposure to mineral wool fibres and skin
problems, itching, eye damage and respiratory irritation. The latter has, in many
cases, led to chronic bronchitis. It is also possible that these materials have car-
cinogenic effects. Acoustic panels functioning as sound insulation are normally the
most common source of mineral wool fibres in the indoor climate (Bakke, 1992).
It has been shown that dampness in mineral wool can lead to the emission of
vapours which can later enter the building. The problem is more acute when the
wall becomes warm, e.g. through solar radiation. The type of gases released are
aliphates, aromates and ketones. The aliphates in particular can affect air quality
detrimentally. All of these gases irritate the ears, nose and throat (Gustafsson, 1990).
Damp mineral wool smells sour, which can imply the release of amines.
Additives in mineral wool that contain nitrogen are very susceptible to mould.
The amount of mould in an infected material can be 1000 to 50 000 times the
amount in uninfected material (Bakke, 1992).
Raw materials are abundant for the main constituents of glasswool and rock-
wool. The production of glasswool occurs in relatively closed processes. The
emissions from production are little and limited to formaldehyde and dust in
addition to energy pollution. Large amounts of phenol, ammonia, formaldehyde
and dust are released during the production of rockwool, and large amounts of
waste are produced. Phenol can be washed out of rockwool waste. Unpolluted
waste can be compressed and recycled for the manufacture of new mineral wool,
although the industry is so centralized that this form of recycling is economical-
ly unrealistic.
Montmorillonite
Montmorillonite occurs mainly in bentonite clay, a very disintegrated type of
clay made from volcanic ash. The minerals in montmorillonite not only absorb
