Civil Engineering Reference
In-Depth Information
in hospitals for example, there is a great energy-saving potential and improved com-
fort if materials with high thermal capacity are used. The same is true for buildings
where there can be wide and rapid changes in the inside temperature, for example,
when opening the windows. The thermal insulation value of a material is reduced
when damp. In frozen materials the ice conducts warmth three to four times better
than water. This is important if using hygroscopic materials. Even if such materials
seldom freeze, a lower insulation value is assumed during spring because of the high-
er moisture content.
Age can also affect insulation value. Certain products have shown a tendency to compress
through the absorption of moisture and/or under their own weight, while others have shrunk
(mainly foam plastics). The thickness of the layers of insulation needs to be appropriate for
the local climate. Too much insulation can cause low temperatures and thereby hinder drying
in the outer layers, which can lead to fungus developing in the insulation or adjoining
materials.
Insulation materials are sold either as loose fill, solid boards or thick matting. The
latter two can result in a damaged layer of insulation, because temperature or
moisture content changes can cause dimensional changes. This is especially the
case with solid boards, which need to be mounted as an unbroken surface on the
structure and not within it. Loose fill insulation is good for filling all the spaces
around the structure, but it can settle after a time. The critical factors are the
weight and moisture content of the insulation. The disadvantages of hygroscop-
ic materials become apparent here because they take up more moisture and
become heavier. Settling can be compensated for by using elastic materials which
have a certain 'suspension' combined with adequate compression. Structures
with hygroscopic loose fill as insulation need topping up during the building's
life span.
Thermal insulation materials usually occupy large volumes, but they are light
and seldom take up more than about 2 per cent of the building's total weight.
Many insulation materials do, however, have a high primary energy use and use
of material resources, and produce serious environmental pollution during man-
ufacture, and use, and even as waste. The waste must often be specially treated.
Only in exceptional circumstances is it possible to recycle or re-use insulation
materials.
Warmth-reflecting materials
By mounting a material that has a low reflection rate for short-wave warm
radiation on the building's south façade, solar energy can be used very effi-
ciently, while a sheet of highly reflective material on the inside of the wall
will reduce heat loss. This is especially utilized in modern window tech-
nology.
