ESD design guide for Australian Government buildings: Edition 2

esd opportunities in building
OPPORTUNITY 4
minimising energy use
“One of the problems with air
based systems is that they
don’t turn down very well. And
when they get to this low load
situation… they perform badly
and get into all sorts of problems
… yet this is the situation for 80%
of the year.”
Appropriate sizing of building systems
Dr Paul Bannister, Managing Director,
Exergy Australia
APPROPRIATE SIZING OF
LIGHTING, HEATING AND
COOLING SYSTEMS
Several concepts need to be
understood, and considered, when
choosing heating and cooling plant:
Natural ventilation
Uses external air and air movement to
ventilate a building.
Mechanical ventilation
Uses machines to move the air – fans,
air conditioners etc.
Mixed mode ventilation
Uses a mixture of natural and
mechanical systems.
Refrigerant cooling
Uses ‘refrigerants’ in heat pump
systems (such as a fridge) to move
heat from one place (such as inside
the fridge) to another place (such as
the back or bottom of the fridge).
Evaporative cooling
Uses the latent energy of water
evaporation to remove heat.
Comfort
A measure of the perception of people
n a space. The Predicted Mean Vote
(PMV ISO 7730-1984) and Adaptive
Comfort (ASHRAE-55 25 ) systems
provide appropriate measures of
comfort. Together they both consider
actors such as radiant temperature,
humidity, radiant symmetry, air
movement, occupant clothing and
activity levels and external ambient
temperatures.
Adaptive comfort
Adaptive comfort assessment
methods allows the designer to
produce a more efficient and smaller
HVAC system.
Radiant cooling/heating
Radiant cooling/heating is the
feeling of heat or ‘coolth’ radiating
from a nearby element (such as
brick wall that has been in sun). A
large percentage of an individual’s
sensation of thermal comfort is from
radiant heat.
Mechanical plant size
Taking passive design elements into
account means that in many cases
the size of the mechanical plant can
be reduced. Setting realistic building
energy needs is also important. This
requires an understanding of how
the building will be used, how many
people will be using it, and for how
many hours.
For example the energy needs for
a 24 hour building that houses a
call centre, with their people and
equipment intensive workspaces,
will be different to a nine-to-five
office housing maintenance staff for
Canberra parks. They may only be in
their office half of the time and spend
most of their time in the field.
Lighting
Lighting needs to be optimised for
the tasks that will be performed. The
simplest ways of minimising energy
consumption from lighting are to
consider:
• energy efficiency fluorescent tubes
(T5 or T8 depending on sitting and
use of light)
• use of natural light
• use of electronic ballasts (7% more
efficient)
• user controls.
25 ANSI / ASHRAE Standard 55-2004, Thermal
Environmental Conditions for Human Occupancy.
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ESD DESIGN GUIDE FOR AUSTRALIAN GOVERNMENT BUILDINGS