Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
6.1. LIGHT SHELVES
Light shelves are sunshades placed inside or outside the window facade and above eye level. They reflect sunlight
and daylight into the interior space. They can at the same time also shade the glass below and reduce unwanted direct
glare into the space. A flat-sloped ceiling extending from the facade edge enhances light distribution and reduces contrast
and glare.
Sloped ceiling reflects
daylight deep into the space
Sunshades
double up
as light
shelves
BENEFITS
•
Maximize daylighting while minimizing solar heat gain
•
Saving in electrical lighting and cooling load required
•
Improve occupant views and comfort
POINTS TO NOTE
•
It is important to note that the best daylight penetration typically results from using light-coloured, sloped
external shelves.
•
It is important to note that reflecting coatings or films should be avoided as they may cause glare problems for
adjacent buildings.
•
To improve light distribution in spaces, higher floor to ceiling height should be used.
•
Light-coloured ceiling, which is free of obstructions for better light penetration should be used.
•
To ensure successful implementation of light shelves, the design and profile of the sunshades should be
carefully analysed and studied. If possible, computer energy simulation should be used to evaluate trade-offs
between daylight transmission and solar control.
6.2. PHOTOVOLTAIC CELLS
Photovoltaic cells convert the sun’s energy into electricity. They rely on the photovoltaic effect to absorb the energy of
the sun and cause currents to flow between two oppositely charged layers.
Together with a backup battery, it is suitable for low-power applications such as powering external street lighting or
devices in remote areas or where connection to the electricity mains would be not cost effective. However, because of
the relatively high cost of purchase and installation, they are not commonly used.
BENEFITS
•
Environmental-friendly electricity supply
•
No need to run electrical wirings
Use for external lighting
Use for water heater
6.3. LIGHT PIPES
Light pipes transmit natural light into deeper interior
spaces to reduce lighting load. Most light pipes consist
of an exterior transparent dome, a reflecting metal pipe
and a diffuser for installation at ceiling.
Light pipes can avoid light loss by using the principle of
fiber optics. However, such light pipes may be still too
expensive for day lighting.
It is suitable for areas where possible fluctuations in
illumination intensity caused by movement of clouds
across the sun are less observable such as public areas,
retailing spaces, basement carparks etc. It is normally
less likely to be satisfactory where fluctuation of sunlight
intensity are more noticeable such as spaces that require
concentration on text such as reading rooms, drafting
areas, etc
Exterios dome
Reflec ting
metal pipe
diffuser
ceiling
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Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
BENEFITS
•
Maximize daylighting while minimizing solar heat gain
•
Savings in electrical lighting and cooling load required
•
Improve occupant views and comfort
Using light pipe in basement carpark
Light pipes above space
Ceiling diffuser –
introduce natural lighting
into space
According to calculations given by supplier, it takes 13 to 14 years for payback on light pipes investment.
POINTS TO NOTE
•
It is necessary to note that light pipes must be located where the sun can shine on them directly. A light pipe
will not produce a useful amount of daylight if it is shaded by adjacent buildings or plants.
•
The light loss is proportional to the length-to-width ratio of the pipe. Therefore, efficiency is sacrificed if the pipe
is too long.
6.4. AUTO CONDENSER TUBE CLEANING
Auto condenser tube cleaning system allows the chiller to maintain good heat transfer with constant cleaning of the
condenser tubes. It is suitable for use in buildings with central air-conditioning system which makes use of water-cooled
heat exchangers or condenser.
BENEFITS
•
Improve the energy efficiency of chillers.
Research has shown that fouling starts to form after 200 to 400 hours. Fouling in condenser tubes will reduce
the heat transfer capacity of the condenser tubes.
•
Lengthen the life span of heat exchangers and condenser systems as the system eliminate the condenser
tubes from scale and fouling and hence, prevent condenser tube corrosion.
•
Lower maintenance costs as there is no need to shutdown the chiller for condenser cleaning.
Auto condenser tube cleaning system
Potential saving
The potential savings are about 10% to 25% as
compared with systems without proper tube cleaning
system.
POINTS TO NOTE
•
It is important to ensure that the auto cleaning system should not damage the chiller when any part of the
system fails.
•
To ensure good performance, the system should also detect and alert any failure within the system so that the
fault can be rectified earlier.
6.5. WATERLESS URINALS
Waterless urinals completely eliminate the use of
water in flushing urinals and save water. It employs an
innovative device where urine passes through a lighterweight liquid. The layer of liquid traps and effectively
seals it from the atmosphere and preventing odours. The
urinal is plumbed to a standard sanitary drain line. As it
is a non-flushing urinal, water connection and flush valve
are not needed.
BENEFITS
•
Save water as no flushing required.
•
Low installation cost as water connection and
flush valve are not needed.
POINT TO NOTE
•
Proper maintenance is crucial to ensure the waterless urinal do not cause unpleasant smells.
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Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
6.6. NON-CHEMICAL WATER TREATMENT
Use non-chemical water treatment system to control bacteria, scale, corrosion, algae and slime. Non-chemical water
treatment system could consist of the following components:
o
an electromagnetic descaler for scale control
o
an electromagnetic magnetite generator for corrosion control
o
a copper-silver ionization unit for bacteria, algae and slime control
BENEFITS
•
Saving in energy consumption due to reduction in scale, corrosion and biofilm
•
Environmental friendly as the system uses no chemical
•
Able to control microbiological growth and minimize Legionellosis disease outbreak
•
Improve cooling tower’s cycle of concentration
•
Discharged blow-down water from cooling tower can be recycled and reused for other needs such as
watering plants
Non-chemical water treatment system
Copper-silver
ionization unit
Inductor coil unit
Electromagnetic
descaler/Magnetite
generator
ELCB/MCB
Transformer
rectifier
6.7. TITANIUM DIOXIDE SOLUTIONS
Titanium Dioxide (TiO2 ) is a type of photocatalyst which will eliminate odours in the air, kill bacteria and decompose
organic matter when exposed to light. When exposed to light, TiO2 activates the oxygen molecules, which decompose
bacteria and germs through photocatalytic activity. It is being used in commercial and healthcare facilities to improve the
hygiene of its environment.
Besides that, it can also be applied on the external facade such as glass, wall tiles and aluminium claddings to reduce the
maintenance and cleaning of external facades. When exposed to sunlight, TiO2 absorbs a portion of the ultra violet light
and becomes hydrophilic where water is not repelled but spreads to form a thin film on the surface. With the combination
of both photocatalysis and hydrophilic effect, TiO2 solution can reduce dirt build up on the external surface.
BENEFITS
•
Coated surface can be cleaner and fresher with less frequent cleaning. Hence, savings in water, cleaning
agents and manpower costs.
•
Elimination of odours
6.8. THERMAL ENERGY STORAGE COOLING
Thermal energy storage cooling utilizes off peak electricity to produce cooling energy in either chilled water or ice. The
system stores the cooling energy in either chilled water or ice storage tank and discharges the stored cooling energy for
air-conditioning during peak cooling time.
It is suitable for buildings with high cooling load requirements and has enough space for thermal energy storage. Figures
below show the typical installation of schematic diagram of chilled water thermal energy storage cooling and ice thermal
energy storage cooling.
BENEFITS
•
Require fewer chillers
•
Saving in electricity cost by using off-peak electricity with low tariff
•
Most of the time, chillers are able to operate at designed optimum capacity with high efficiency
•
Environment-friendly system
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Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
Chilled water thermal storage cooling
Ice thermal energy storage cooling
Source: Schematic diagrams from EnE System
6.9. ULTRAVIOLET-C (UVC) EMITTER
UVC emitter can be installed after the cooling coils of AHUs and FCUs to keep the coils clean without the need
for washing and chemical cleaning. UVC emitter produces high output of UVC photons to destroy bacteria, viruses
and mould.
A case study by Florida Hospital showed that installing UVC emitter in AHU significantly reduced the need of coil-cleaning
and also saved energy. UVC emitter in AHU provides continuous disinfection and coil cleaning.
BENEFITS
•
Save manpower, water and cleaning chemicals and prolong the life of the coils
•
Improve indoor air quality as UVC light from the emitters destroy bacteria, viruses and mould and eliminate
odours
AHU with UVC emitter
Potential saving
Clean coils help to improve the heat transfer between
air and coils. A saving of between 15 to 30% of airconditioning energy can be achieved by installing UVC
emitter.
6.10. FUEL CELL
A fuel cell is an electrochemical energy conversion device that combines hydrogen and oxygen from the air to produce
electric power without combustion. It is suitable for use as backup power such as replacing uninterruptible power supply
(UPS) for hospitals, institutions etc.
BENEFITS
•
No pollutant byproduct using hydrogen as the fuel. The fuel cell energy is produced through a clean
electrochemical reaction that releases only water.
•
The main advantage of using fuel cells over UPS is that the latter generates heat continually even when the
batteries are under float-charge. This increases the building’s energy cost.
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Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
Location of fuel cell unit
Fuel cell system
6.11. SELF CLEANING FACADE SYSTEM
External cladding such as ceramic cladding with hydrotect coating will provide self cleaning properties. The effect of
hydrotect is based on the principle of the photocatalysis. Sunlight ensures the decomposition of organic material such
as algae and fungi. Besides that, when exposed to sunlight, the coating absorbs a portion of the ultra violet light and
becomes hydrophilic where water is not repelled but spreads to form a thin film on the tile surface. This enables the dirt
to be easily removed. With the combination of both photocatalysis and hydrophilic effect, substantial reduction in external
facade cleaning costs can be achieved due to longer cleaning intervals.
BENEFITS
•
Low cleaning costs
•
Decomposition of bacteria, fungi, algae and germs.
•
Environmental-friendly
6.12. INTEGRATION OF SMOKE CONTROL SYSTEM WITH AIR-CONDITIONING
& MECHANICAL VENTILATION SYSTEM
For buildings with substantial areas that required both smoke control and air-conditioning system, efficient use of natural
resources can be achieved by integrating both systems together.
BENEFIT
•
Save construction materials and installation costs
POINTS TO NOTE
•
As this system requires the use of fire-rated ducting, waiver has to be sought from Fire Safety Shelter
Department to reduce such requirement.
•
Software simulation may be done to ensure that the system can perform to meet the design requirements. For
example, using Computation Fluid Dynamic software simulation to predict the fire scenarios.
6.13. LOW FLOW HIGH TEMPERATURE CHILLED WATER SYSTEM
Design chilled water flow based on more than 8.3°C temperature differences instead of the norm of 5.5°C (i.e. 6.7°C
to 12.2°C). This design is suitable for building with water-cooled central air-conditioning with high pumping head. It is
commonly used in district cooling plant.
BENEFITS
•
Saving on operating cost due to smaller pumps.
•
Saving in building material costs through downsizing pumps, pipes, valves and insulation.
POINT TO NOTE
•
Although there will be penalty for chiller efficiency associated with lowering of the leaving water temperature
but the overall savings in distribution power, especially for building with high pumping head, would still be
significant. For example, building with more than 30m pump head would be considered a good choice for
using this system.
6.14. HEAT RECOVERY DEVICES
To save operating cost, heat recovery devices can be used on air-side and/or water-side, as follows:
o
Use heat recovery wheels, heat pipe, coil loop etc on airside system.
o
Use heat pumps or heat machines to harness waste heat from condenser and improve efficiency of chiller or
condensing units.
6.15. PNEUMATIC WASTE CONVEYANCE SYSTEM
Pneumatic waste collection system can be used to reduce odour from
refuse and improve hygiene. The refuse thrown into chutes will be sucked
through closed piping into a central collection bin at regular interval. This
is a more efficient and odourless means of refuse collection. The refuse
stored in the central collection bin will be picked up by refuse truck. This
limits the movement of refuse trucks and promotes a cleaner and more
pleasant environment.
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Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
BENEFITS
•
Savings on manpower cost to move refuse.
•
Better hygiene and cleanliness, eliminating pest and odour related problems.
POINT TO NOTE
•
It is important to carefully position the discharge of the transported air after passing through a cleaning filter.
6.16. COOL PAINTS
Cool paints when applied on the roofs or exteriors of building can significantly decrease indoor room temperature and
hence reduce cooling load required. Cool paints have high solar reflectivity as compared to conventional roofing material
or exterior surface. According to tests conducted by the University of Athens, the surface temperature of external surface
coated with new generation cool paints are 6°C lower than the surface temperature of white marble.
6.17. WATER RECYCLING PLANT FOR CONSTRUCTION USAGE
During construction period, water recycling plant can be used to reduce the dependence of PUB water. For example,
more cost effective method of water treatment such as membrane technology can be used.
BENEFITS
•
Achieve less reliance on PUB water.
•
Eco-friendly system
Water recycling plant used in a construction site which uses membrane technology
and auto-cleansing system
6.18. BUILDING INTEGRATED PHOTOVOLTAICS (BIPV)
BIPV is a system where photovoltaic panels are integrated into the design of a building so that the solar components
also serve as structural or design elements. Photovoltaic technologies use solar energy to produce electricity in an
environmental friendly way. To offset the cost of building facade, roofing or glazing, BIPV systems should be integrated
into a building during the initial design stages. The BIPV system can be used for:
•
Roofing
•
Facades, windows and curtain walls
•
Skylights and atrium areas
BENEFITS
•
Offsets the cost of facade, roofing, etc
•
Low maintenance cost and long life span
•
Savings in electricity costs
•
Environmental-friendly electricity supply
Savannah Condominium Club House with BIPV system
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Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
6.19. TRI-GENERATION PLANT
Conventional power plant converts only less than half of the fuel energy into electricity and the rest of the energy losses
as heat. Tri-generation plant recovers the “waste” heat to produce chilled water for centralized air conditioning system.
The Tri-generation plant comprises fuel cells or gas turbines to produce electricity and heat together with absorption
chillers. The chillers will use the generated heat to produce chilled water. Figure below shows how the plant works.
The plant offers a more flexible and economical solution to ensure uninterrupted supply of electricity, chilled water and
hot water.
6.20. CASE STUDY
The Nanyang Polytechnic has implemented a number of creative projects to continually reduce the electricity and water
consumption where practical. Some of the projects may be very simple but are very effective and result in significant
savings. Some of the main innovative projects are listed below.
1. Innovative Bollard Lights for landscape
•
A bollard fixture to give not only lateral but vertical lighting was designed. Conventional bollard light can only
give lateral lighting and required another up-lighter to give vertical lighting.
•
Using energy efficient lamps
•
A cost comparison shows a payback period of less than 3 years.
2. Reconfiguration of roads, car parks and landscape lights
•
Streetlights and car park lights circuits are reconfigured into different electrical phases to allow parts of the
lights to be turned-off after midnight where there is little utilization
•
The control of landscape lights, streetlights and car park lights are reconfigured to allow more flexibility
•
With the reconfiguration, savings of 30% on electricity consumption is achieved with a payback period of
about 6 months.
3. District Cooling System
•
Adopting energy efficient central district cooling system to provide cooling needs for campus airconditioning.
4. Effective management of air-conditioning system
•
Implementation of automated control to allow a window period for fan coil units (FCUs) operation so that the
FCUs will not be left operating when not needed
•
Implement differential pressure control at the respective air-conditioning zones
•
Create alert signals when room temperature is too low
•
Conceal FCU thermostats to prevent unnecessary user adjustment of temperature set-point
•
The improvement results in savings of about 3% on electricity consumption with payback period of about
3 months.
5. Energy recovery in the mechanical ventilation system for fume cupboards
•
Instead of discharging air-conditioned air fume cupboards directly outdoor, the air is used to cool incoming
replacement air via a heat exchanger using water as the heat transfer medium. This helps to pre-cool
replacement air to a temperature of about 25°C, hence preventing energy wastage.
6. Optimizing the use of fertilizers and pesticides to trees
•
In the previous practice, the fertilizers were being thrown and scattered onto the planting areas and the
pesticides were manually sprayed onto trees. The manual method incurred high cost and also resulted in
environmental pollution.
•
In the new practice, a UPVC pipe is inserted into the ground with only the top cover exposed above
ground. Instead of pellet form fertilizers, slow release fertilizers are used together with systemic fungicide
and insecticide: the ratio is 70%, 15% and 15%. With this new solution, the fertilizers and pesticides
consumption was reduced by 50% with a payback period of about 10 months.
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Green Building Design Guide
6.
Air-Conditioned Buildings
INNOVATIONS
7. Improvement on irrigation system
•
Installation of rain sensors to cut off the irrigation process when it rains.
•
Installation of timers to control the operation of the pump. This will save the electricity needed to operate
the pumps to maintain the system pressure.
•
This results in savings of about 23% of water consumption a year.
Rain sensor
Auto turn off irrigation system
8. Optimizing the watering system for hockey pitch
•
The hockey pitch watering system consists of a water tank linked to water pump which is linked to 4 spray
guns at the sides of the hockey pitch. When switched on, the 4 spray guns spray water over the hockey
pitch for 7 minutes at the same time. Only about 75% of the pitch surface area would be fully watered.
•
With the installation of the new controller and control mode, the spray guns will be operated in pairs,
resulting in the average spraying time being reduced. Pitch surface area covered was also increased from
about 75% to almost the entire surface area.
9. Collection and usage of ground water
•
A water tank is constructed at the lowest part of the campus ground. Underground water from various parts
of the campus is diverted from open drains into the tank.
•
The water is subsequently used for irrigation and cleaning.
•
The usage of PUB water for irrigation and cleaning for targeted areas is therefore reduced. The payback
period is about one year.
10. Innovative use of natural resources
•
Rainwater and groundwater was collected at various locations in the campus for irrigation, cleaning and
water spraying operations for hockey pitch. Based on the Meteorological Department’s annual rainfall
statistics and data analysis on the water catchments areas, it is found that there is excess water being
collected, especially during wet session.
•
To further enhance the usage of this excess water, a water transfer system is implemented to divert the
excess water to existing water storage tank.
•
A saving of about 5,000m3 of PUB water is achieved with a payback period of about 21 months.
11. Reduction of algae formation through use of floating fountain
•
Profuse algae formation in koi ponds results in low pond surface visibility and high operating cost.
•
Floating fountains are installed to release the build up of CO2 and increase the O2 level and reduce profuse
algae multiplication. This improves the pond surface visibility and saves operating cost. The payback period
is about 13 months.
12. Creative use of motion sensors
•
Dual-technology motion sensors are installed to control the air-conditioning system for areas with irregular
usage such as staff gymnasium. The motion sensors are also linked to the mechanical ventilation system
and lightings. By-pass switches are provided in case the sensors fail to activate the air-conditioning
system.
•
It is further enhanced by linking the air-conditioning compressor with the campus’ security monitoring
room which is operational 24-hours. This will ensure there will always be minimum load for the air-conditioning
compressor. Hence the compressor will not be worn out too fast because of frequent switching on/off
created by the motion sensors.
•
A savings of about 40% of electricity consumption is achieved with a payback period of about 4 years.
13. Use of solar energy for water heater and lamp posts
Use solar energy for water heater
Use solar energy for lamp-posts
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