Rajesh Srivastava writes about some key challenges faced while
designing and building the façade of an airport.
Modern airport designs often incorporate extremely
large areas of glass façades, probably in part due to
the overall trend in construction industry driving
ever more glass on building façades, and in part due to the
architect’s desire to afford passengers unobstructed views
on the surroundings, as well as on planes landing and
taking off.
One of the first considerations that typically come to mind
when designing the glazed façade of an airport is that spaces
tend to be very large, and thus are difficult to heat up in
winter and to cool down in summer. The façades should be
designed in such a way as to minimise heat flow, thus
reducing the heating or cooling needs. This can be done in a
variety of ways, depending on climatic conditions.
In areas where there are large seasonal variations, with
cold winters and hot summers, thermal conduction
through the façade represents an important factor to
control. This is measured by a performance parameter
called U-value. This represents how much heat enters (or
exits) the building by unit of façade, based on the
temperature difference between the inside and the
outside of the building. There are several ways of
controlling the U-value of the building. The first one is to
reduce the wind-to-wall ratio. Spandrel panels are
typically insulated, and thus offer very low U-values. This
particular technique may not be compatible with the
architectural design, though. The second technique
consists in adopting double-glazed units (DGUs) for
vision areas. DGUs have a much lower U-value than
monolithic glazing (less than half, typically). When this is
not sufficient, a third technique involves filling DGUs
with a rare gas such as argon, which further lowers the value
for even greater efficiency.
Another aspect of heat losses through the façade is related
to radiant heat (infra-reds). To minimise this type of heat
loss, glazed panels can receive a layer of ceramic frit (a
type of permanent paint) that helps reduce heat flow
through the façade. The colour and density of the frit
needs to be selected judiciously so as not to hamper
outward view through the glass. One alternative that can
be used in combination or independently from the one
above is to use low-emissive glass. This type of coated glass
helps reduce infra-red transmission, while allowing
natural visible light to enter the building. Low-emissive
coatings incidentally also help reduce the U-value
discussed above, which represents a double benefit of this
approach. Glass colour also plays an important role in this
respect. Green and blue glass generally perform best
(more light than heat flows through), while grey glass is
the worst overall (more heat comes in than visible light).
As a last resort or if mandated by aesthetics, external
shading devices can also be used on the façades.
As much as it is important to control heat and visible light,
reflectivity can make or break the façade of an airport. If
the façade material is too reflective (glossy metal
cladding, reflective glass, etc.), it may affect pilots landing
and taking off, as well as controllers in the control tower.
This represents a potential danger, thus needs attention.
It may not be very easy to control with complex,
articulated façades, since reflectivity varies with the angle
at which the surface is viewed.
One other important consideration when designing the
façade of an airport is acoustic control. Planes can generate
very high noise levels. Sound transmission through the
façade should be controlled to reduce this noise to acceptable
levels within the airport. Fortunately, airports are typically
fairly noisy places, given the high density of people and the
level of activity inside, thus the noise criteria is not extremely
stringent. Typically, laminated glass or DGUs are sufficient to
achieve acceptable noise levels internally. If higher levels of
noise cut-off are required, then it is possible to consider
laminated DGUs, which offer outstanding noise-reduction
performance. The actual solution varies from airport to
airport, depending on local regulations, as well as the
expected size of aircrafts that will be using the airport.
This last point also ties in with “wind loads” on the façade.
Reactors of large aircrafts can generate tremendous draft,
which can affect the façade of the terminal. Airports are
often designed with “blast barriers” to divert these air jets
away from the façade, but in cases where the façade will be
subjected to heavy gusts from aircraft engines, designers
should ensure that glass or cladding panels are secured
and won’t be blown away.
While on the topic of blasts, airports are valuable
infrastructure assets for a country, and as such are often the
target of terrorists. In cases where local security forces
envisage a potential threat, airports façades need to be design
with blast mitigation measures. This can range from simply
extending the stand-off distance, thus reducing potential
damage, to hardening measures preventing a blast from
having a large impact on the structure and its users.
Designing and building the façade of an airport presents
some key challenges. This brief overview provides a glimpse
into some of the technical issues that designers are faced
with, as well as some solutions that can be implemented to
address those issues. However, the actual implementation of
these measures requires a large amount of knowledge and
experience in the particular requirements of airports.
(The writer is Managing Director – Meinhardt India.)