Civil Engineering Reference
In-Depth Information
heat. This causes the straw to release its own form of glue that binds the whole
board together. Porous boards have a thermal insulation equivalent to woodwool
slabs. Under damp conditions they will be exposed to attack by fungus. Straw
boards can also be produced as hardboards (see 'Production of straw boards',
p. 359).
The first insulation boards made of straw were produced as early as the 1930s.
They were made in thicknesses of 5-7 cm, under low pressure, reinforced with
crosswires and covered with paper.
Flax boards are made of flax fibres boiled under pressure for several hours.
The material is highly durable and non-flammable, and is used in some fire
doors.
Linseed oil putty
Linseed oil comes from the seeds of the flax plant. Putty is a product of the work-
ing of a mixture of linseed oil and stone flour, such as chalk, heavy spar, pow-
dered fired clay, powdered glass, etc.
Linseed oil putty is the only alternative to plastic-based mastics and window
putties. It is environmentally much sounder than the alternatives, with no nega-
tive effects during production or use. As a waste product, it can be used in fill as
long as no additives (e.g. lead) have been mixed in, to improve its elasticity. The
elastic qualities of the putty can be preserved for a long period by painting with
oil-based paint. Despite this the putty will eventually harden and begin to crum-
ble. Linseed oil based putty must not be used in contact with damp lime or
cement surfaces.
Bogpeat
Peat has been used a great deal as an insulating material and moisture regulator
in its natural state or as a loose material, granules, mats or boards. In the past it
has been used in Germany, Ireland, Scandinavia and Scotland. Today, insulation
products of peat are again being produced in Sweden.
Peat usually consists of decayed brushwood, plants from marshes, algae and
moss. For building, the most important moss is found in the upper light layer of
a bog and has not been composted. Older, more composted peat can be used in
certain circumstances, but it has a much lower insulation value. Totally black
peat is unusable.
Peat is a good sound insulator, because of its weight, and could in many cases
replace heavier alternatives such as sand in floor construction.
The same pigment substances that are in our skin are also found in peat. It will
therefore probably protect us from certain frequencies of electromagnetic radia-
tion. Matting made of peat can filter and absorb emissions of radon from build-
ing materials and foundations.
