Key concepts in sustainable building - The Hempcrete Topic: Designing and Building with Hemp-lime - page 77

A particular quality of most natural materials that is not shared by most synthetic materials
is that they act in a 'hygroscopic' way. This describes the ability of a substance to attract
and hold moisture from the nearby air. Cellulose-containing natural insulation materials,
such as wood, hemp and straw, are good at doing this because of their micro-porous struc-
ture at a cellular level. Natural materials therefore have the ability to 'buffer' moisture
levels in the indoor atmosphere, by absorbing water vapour during times of high relative
humidity and releasing it again when the relative humidity of the surrounding air falls. This
has important implications for the health of a building's occupants (see page 65 ) .
A new-build housing estate constructed with structural timber frames and hempcrete or wood-fibre
insulation.