First Principles - Sustainable Design: The Science of Sustainability and Green Engineering - page 69

example of the variables):

λ
ρ w gR

σ

2 cos

h capillary = (2.17)

where

fluid surface tension (g s − 2 ) σ =

λ = angle of meniscus (concavity of fluid) in capillary (degrees)

fluid density (g cm − 3 ) ρ w =

gravitational acceleration (cm s − 1 )

g =

R = radius of capillary (cm)

Capillarity and surface tension are important to green design for numerous
reasons. This is one of the means by which water permeates materials, bringing
with it contaminants and nutrients, such as those that cause the growth of mold
and other fungi. It is also the principal means by which roots obtain nutrients.
In fact, one of the growing applications of root transfer is phytoremediation of
hazardous waste sites. Plant life is used to extract contaminants (e.g. heavy metals)
from soil which is translocated to the stems and leaves, which are harvested and
taken away. The soil grows progressively cleaner with time.

Sidebar: Applying the Synthovation/Regenerative Model:
Fluids and Buildings
Fluid dynamics and pressure relationships are examples of physical factors that
can make or break a green design: for example, when designing a building, a
working knowledge of how temperature and other indoor and outdoor factors
can greatly affect the indoor environment and create opportunities to build
more efficient air-handling systems. Cooling and heating the air can be done
more efficiently and effectively in achieving the objective of providing comfort
for the occupants by incorporating the shape of rooms, the interrelationships
of these rooms (vertically and horizontally), and air movement into the design
at the outset (see Fig. S2.7). If we consider fluid dynamics early, we can control
the transport mechanisms to our advantage and use less energy to temper the
environment. For example, in winter, our design will use natural processes
to circulate air; warm air is sent to nonliving spaces in summer and to living
spaces in winter.
By applying scientific principles and understanding of the natural tendency
for air to stratify in layers of various temperatures, architects and engineers are