Building with earth - Gernot MINKE (1)

Water content (g/m 3 )
0.5
0.4
0.3
0.2
1 Sandy loam 1900 kg/m 3
2 Silty loam 1950 kg/m 3
3 Straw loam 1200 kg/m 3
4 Straw loam 550 kg/m 3
5 Straw loam 450 kg/m 3
6 Mineral loam 750 kg/m 3
7 Mineral loam 600 kg/m 3
Water content (g/m 3 )
0.5
0.4
0.3
0.2
1 Solid brick 1850 kg/m 3
2 Hollow brick 1200 kg/m 3
3 Lime-sand brick 1800 kg/m 3
4 Porous concrete (Hebel) 600 kg/m 3
5 Porous concrete (Ytong) 450 kg/m 3
6 Cement concrete M25 2200 kg/m 3
2.27 Drying period of
loams and other building
materials
2.28 The vapour diffusion
coefficient µ of different
loams and plasters
according to the German
standard DIN 52615, wet
method
2.29 Absorption curves
of solid (left) and lightweight
(right) loams
2.30 Equilibrium moisture
content of different
loams and other building
materials
2.31 U-values of loam
0.1
0.1
0.0
0.0
Drying time (d)
Drying time (d)
2.27
Condensation
In moderate and cold climatic zones, the
water vapour contained in indoor air diffuses
through the walls to the exterior. If the air
is cooled down in the walls and reaches its
dew point, condensation occurs. This dampness
reduces thermal insulation capacity and
may lead to fungus growth. In such cases, it
is important that this humidity be transported
quickly by capillary action to the surface
of the walls, where it can evaporate. Therefore,
materials like loam with a high capillarity
are advantageous.
In order to reduce the danger of condensation
in walls, vapour transmission resistance
should be higher inside than outside. On
the other hand, resistance to heat transfer
should be higher outside than inside.
Though the above principles normally suffice
to inhibit the formation of condensation
in walls, it is also possible to create a vapour
barrier on the inside by utilising paints or
sheets.
It should be mentioned, however, that
vapour barriers have two important disadvantages.
• Vapour barriers are never fully sealed in
practice, especially at joints, as in walls with
doors, windows and in ceilings. Harmful
condensation can occur in these joints.
• With monolithic wall sections, water penetrates
in the rainy season from the outside
into the wall, and then cannot evaporate
Water Content W (%)
1 Clayey loam
2 Silty loam
3 Sandy loam
4 Granular clayey loam
Relative humidity (%)
5 Loam brick
6 Kaolinite, pulverized
7 Bentonite, pulverized
Water Content W (%)
1 Straw loam 450
2 Straw loam 850
3 Straw loam 1200
4 Loam with expanded clay 450
5 Loam with expanded clay 550
Relative humidity (%)
2.29
6 Loam with expanded clay 700
7 Expanded clay particles
8 Expanded glass particles
9 Rye straw
30
Properties of earth