The thermal conductivity (the l-value) of several alternative
insulation products and a traditional product is determined under
different humidity conditions in a specially constructed hot plate
apparatus.The hot plate apparatus is constructed with an air gap
on each side of the test specimen where humidified air can pass.
Thus, it is possible to build up different degrees of moisture on
each side of the test specimen.The thermal conductivity is
determined for the following types of alternative insulation:
sheep's wool, flax, paper insulation, perlite and mineral wool.
The insulation products were Ekofiber Vind, Herawool (without
support fibres), Heraflax, Isodan with and without salts, Miljø
Isolering with and without salts, Perlite (water-repellent), and
Rockwool A-batts for comparison.All measurements of the materials
started with no affection of moisture. Nevertheless, results were
achieved, with and without affection of moisture, which were 0-20%
higher than expected for the materials used. The measurements of
the existing investigation should therefore not be considered
giving real absolute values of the thermal conductivity. They can,
however, indicate the relative significance of the moisture
level.For all the materials the thermal conductivity shows only a
small dependence of the moisture level until this reaches a
certain high level (average RH above appr. 75%). Over this level
the thermal conductivity rises considerably - by up to 50%.
However, this increase is presumably caused by an accumulation of
moisture as condensation in the parts of the insulation that lie
immediately close to the cold side of the apparatus. The high
l-values found are therefore of no practical importance in
structures where no condensation occurs. Disregarding these
condensation situations, the maximum increase of the thermal
conductivity is 3-8% because of the hygroscopic uptake of humidity
from the ambient air.
|Number of pages||24|
|Publication status||Published - 1999|