DEPARTMENT OF RURAL AND URBAN PLANNING
HRUP LEVEL THREE
ENVIRONMENTAL DESIGN TWO [RUP 302]
Explain why environmental lighting, transmission of sound and ventilation rates are critical in
the design of the built environment. As an urban designer how would you design for these
components at the urban micro and macro levels?
21 OCTOBER 2011
UNIVERSITY OF ZIMBABWE 2011
In the design of a built environment environmental lighting, transmission of sound and
ventilation rates are critical factors to be taken into consideration as they ensure thermal comfort
and health to both animals ...view middle of the document...
Ventilating has two types which are forced and natural ventilation.
As an urban environmental designer one should mostly design his or her built environment
naturally so as for sustainability and well as for aesthetics. Natural ventilation is the ventilation
of a building with outside air without the use of a fan or other mechanical system. It can be
achieved with openable windows or trickle vents when the spaces to ventilate are small and the
architecture permits. In more complex systems warm air in the building can be allowed to rise
and flow out upper openings to the outside (stack effect) thus forcing cool outside air to be
drawn into the building naturally through openings in the lower areas. These systems use very
little energy but care must be taken to ensure the occupants' comfort. In warm or humid months,
in many climates, maintaining thermal comfort solely via natural ventilation may not be possible
so conventional air conditioning systems are used as backups. Air-side economizers perform the
same function as natural ventilation, but use mechanical systems' fans, ducts, dampers, and
control systems to introduce and distribute cool outdoor air when appropriate.
Natural ventilation involves harnessing naturally available forces to supply and removing air
through an enclosed space. There are three types of natural ventilation occurring in buildings:
wind driven ventilation, pressure-driven flows, and stack ventilation. Natural ventilation is
generally impractical for larger buildings, as they tend to be large, sealed and climate controlled
(Osbourn 1985).Also natural ventilation is ensured when buildings are built next to trees so as to
ensure fresh air. At the University of Zimbabwe there are more tall trees near the buildings,
though the trees act as wind breaks they also ensure that fresh air is provided.
A very good example for natural ventilation is the Eastgate centre which was designed to be
ventilated and cooled by entirely natural means; it was probably the first building in the world to
use natural cooling to this level of sophistication. Eastgate centre is on Robert Mugabe Avenue
and Second Street. The Eastgate Centre's design is a deliberate move away from the "big glass
block". Glass office blocks are typically expensive to maintain at a comfortable temperature,
needing substantial heating in the winter and cooling in the summer. They tend to recycle air, in
an attempt to keep the expensively conditioned atmosphere inside, leading to high levels of air
pollution in the building.
Artificial air-conditioning systems are high-maintenance, and Zimbabwe has the additional
problem that the original system and most spare parts have to be imported, squandering foreign
exchange reserves. On Eastgate centre there is air cooling by passive means; complete sun
control; external glass, no more than 25 percent of the external wall; natural and artificial light
balanced and glare controlled; a large part of the surface area of the...