Civil Engineering Reference
In-Depth Information
Table 14.1:
The approximate reflection
factor of solar radiation on different
materials
Material
Reflection
Shiny aluminium
0.70
Aluminium bronze
0.45
Brick
0.14
Timber
0.14
White paint
0.70
Light paint
0.70
Black paint
0.01
Moisture-regulating materials
Moisture should not be able to force its way into a building's structure without
being able to come out again. Apart from the danger of mould and rot within
organic materials, the damp can freeze and cause the breakdown of mineral
materials when frost occurs. Damp also reduces the insulation value of the mate-
rial drastically.
Moisture can enter the structure in six ways:
• As moisture from the building materials
• As rain
• From the ground
• As air moisture from inside or outside
• As moisture from installations which leak, e.g. drainage, water supply or heat-
ing system
• As spilled water
The last two points do not need to be discussed, as the correct use of a material
should prevent such circumstances, or at least minimize them.
Moisture within building materials
During construction a new house carries about 10 000 litres of water within its
building materials. Drying time is strongly dependent upon the structure of the
material. There is an unnamed relative material factor,
s
- the drying capacity of
a material increases when the factor value falls. Lime mortar has an
s
-factor of
0.25, brick 0.28, timber 0.9, lightweight concrete 1.4 and cement mortar 2.5.
