Resources - The Ecology of Building Materials - page 9

Simply put, twice as much damage to the environment can be tolerated for a
product that lasts 60 years compared with one that lasts 30 years. The lifespan of
a material is governed mainly by four factors:
• the material itself, its physical structure and chemical composition
• construction and its execution; where and how the material is fitted into the
building
• the local environment; the climatic and other chemical or physical conditions
• maintenance and management.
The life span of a roof tile, for example, is not only dependent on the type of clay
used, but also on the immediate environment of the building in which it is used.
A high moisture content during winter can cause frost damage even in the high-
est quality tiles.
The best way to find the anticipated life span of a material is through experi-
ence and tabulated results from real situations. The real situation must have a
comparable local climate.
It is difficult to anticipate the life span of most new materials, e.g. plastics. It is
possible to create accelerated deterioration in laboratories, but these generally
give a simplified picture of the deterioration process than the more complex actu-
al situation. Results from these tests can only be taken as a prognosis. It is neces-
sary to evaluate the role of the material in construction very carefully for such a
prognosis.
We should also remember that durability is not only a quantifiable technical
property. Durability also has an aesthetic and fashionable side to it. It is quite a
challenge to design a product that can outlast the swings of fashion. Especially
with technical equipment, it is also important to consider an optimal durability
rather than a maximum durability. Changes to new products can often show a
net environmental gain in terms of energy-saving criteria.
Effects of the climate and durability
Even if we do not know all the durability factors, it is still certain that climate is a factor that
regulates the life span of a material:
Solar radiation. Ultraviolet radiation from the sun deteriorates organic materials by set-
ting off chemical reactions within the material and producing oxidation. This effect is
stronger in mountainous areas, where the intensity of ultraviolet radiation is higher, and it
also increases as you move further south.
Temperature. An old rule of thumb tells us that the speed of a chemical reaction dou-
bles for every 10°C increase in temperature. Higher temperatures should therefore
increase the deterioration of organic materials. Emissions of formaldehyde from chipboard
with urea-based glue is doubled with every 7°C increase of temperature. Warmth also
stimulates deterioration processes in combination with solar radiation, oxygen and mois-
ture.