Opportunities for improving energy performance in commercial buildings

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This article explores the various opportunities available to improve energy performance in new and exisiting commercial buildings.

Key building design criteria for energy

The main techniques for the minimisation of energy consumption in the design stage are:

• passive design — the name given to any design technique that requires no active (energy using) intervention. An example of passive design is the use of thermal mass (e.g. a large slab of concrete) to absorb heat generated in a building during the day and then using night purging to cool the thermal mass.
  Passive design makes use of natural energy flows as the primary means of harvesting solar energy. Passive design systems can provide space heating, cooling load avoidance, natural ventilation, water heating and daylighting. Passive design is an approach that integrates building components, exterior walls, windows and building materials, to provide solar collection, heat storage and heat distribution
• appropriate sizing of lighting, heating and cooling systems
• appropriate zoning and sensors to maximise efficiency of HVAC and lighting, and to take advantage of passive design features
• appropriate building management, including equipment purchasing
• use of renewable energy
• minimising embodied energy in materials
• commissioning
• operation
• maintenance.
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HVAC opportunities

• Maximising natural ventilation
• Correctly sizing the selected system
• How to improve existing HVAC systems
• Alternative HVAC systems
• Maximising natural ventilation

A heating, ventilation and air-conditioning system (HVAC) is designed to maintain and control air temperature, humidity and quality. It is needed in most buildings to provide comfort for the occupants and to ensure that equipment works properly. It is important to maintain a whole-system approach to the HVAC, as this will result in a much more energy-efficient system than considering components separately. The key to saving energy lies in sizing, installing, commissioning, maintaining and operating the HVAC system correctly. It is important to choose the correct technology and type of system for the organisation. Since heating and cooling are major contributors to peak demand for energy, they contribute disproportionately to energy bills, which increasingly include extra charges for high energy demand. This means great savings can be made by increasing HVAC efficiency. Other benefits include better working conditions and health for occupants.

Maximising natural ventilation

Maximising the use of natural ventilation in commercial buildings is often a highly effective means of lowering the operating costs of HVAC systems (Center for the Built Environment, 2005). This is usually called 'mixed-mode' (sometimes referred to as hybrid) and refers to an approach to space conditioning that uses a combination of natural ventilation from operable windows (either manually or automatically controlled) and mechanical systems that include air distribution equipment and refrigeration equipment for cooling. A well-designed mixed-mode building begins with intelligent façade design to minimise cooling loads. It then integrates the use of air-conditioning when and where it is necessary, with the use of natural ventilation whenever it is feasible or desirable, in order to maximise comfort while avoiding the significant energy use and operating costs of year-round air-conditioning (Center for the Built Environment, 2005).

There does not seem to be a standard mixed-mode approach in practice today — each building continues to be unique. Yet there are a number of classification schemes that describe the integration of natural ventilation and air-conditioning control strategies, usually in terms of whether they exist in the same space, or operate at the same time.

Concurrent mixed-mode operation (same space, same time)

Concurrent mixed-mode operation is the most prevalent design strategy in practice today. In this model, the air-conditioning system and operable windows operate in the same space and at the same time. The HVAC system may provide supplemental or 'background' ventilation and cooling, while occupants are free to open windows based on individual preference. Typical examples include open-plan office space with standard VAV air-conditioning systems and operable windows, where perimeter VAV zones may go to minimum air when sensors indicate that a window has been opened (Center for the Built Environment, 2005).

Change-over design (same space, different times)

Change-over designs, where the building 'changes-over' between natural ventilation and air-conditioning on a seasonal or even daily basis, are becoming increasingly common. The building automation system may determine the mode of operating based on outdoor temperature, an occupancy sensor or a window (open or closed) sensor, or on operator commands. An example of a change-over system is individual offices with operable windows and personal air-conditioning units that shut down for a given office any time a sensor indicates that a window has been opened. Another example is a building envelope where automatic louvres open to provide natural ventilation when the HVAC system is in outside air economy mode, and then close when the system is in cooling or heating mode. However, there are risks with poor maintenance and operation when using economy cycles and they are not necessarily appropriate to all climates (Center for the Built Environment, 2005).

Zoned (different spaces, same time)

Zoned systems are also common, and exist where different zones within the building have different conditioning strategies. Typical examples include naturally ventilated office buildings with operable windows and a ducted heating/ventilation system, or where supplemental mechanical cooling is provided only to conference rooms. For many mixed-mode buildings, operating conditions sometimes deviate from their original design intent (e.g. a building originally designed for seasonal change-over between air-conditioning and natural ventilation may, in practice, operate both systems concurrently) (Center for the Built Environment, 2005).
Mixed-mode buildings offer a variety of advantages over sealed air-conditioned buildings:

• Reduced HVAC energy consumption: A well-designed and properly operated mixed-mode building can scale back or eliminate the use of mechanical cooling and ventilation systems throughout much of the year, with associated reductions in pollution, greenhouse gas emissions, and operating costs. Ventilation with cool outside air can reduce a commercial building's energy use by 15%-80%, depending on climate, cooling loads and building type.
• Higher occupant satisfaction: Occupants typically want windows that can open. Mixed-mode buildings have the potential to offer occupants higher degrees of personal control over their local thermal and ventilation conditions, as well as a greater connection to the outdoors. Past research has found that building occupants accept a wider range of indoor thermal conditions when they are provided with some measure of personal control. Occupants in different climate regions are also more accepting of a range of indoor conditions if they are acclimatised.
• Highly 'tuneable' buildings: Mixed-mode strategies provide inherent flexibility and redundancy in the space conditioning systems of a building, resulting in potentially longer life, greater adaptability to changing uses, and reduced life cycle costs. With the careful application of mixed-mode cooling and ventilation, one can anticipate somewhat smaller mechanical systems and extended HVAC equipment life.

However, mixed-mode buildings also have some potential disadvantages. Mixed-mode strategies have the potential to add cost and complexity to a building, and in the worst case, might yield frustrated occupants and excess HVAC energy consumption. Because the industry is less familiar with mixed-mode buildings, more design time might be needed than with conventional buildings with standard HVAC systems. There is a concern in the industry that concurrent mixed-mode schemes may result in wasted energy if air-conditioning and natural ventilation are occurring in conflict with one another. However, there have been no studies to determine under what situations this might occur. The need for humidity control in some climates may also exacerbate this conflict between the benefits of a sealed and permeable envelope. In addition, it is recognised that natural ventilation may be undesirable in some situations, due to air-borne pollutants and allergens or outdoor noises (Center for the Built Environment, 2005).

Correctly sizing the selected system

Source: Moller & Thomas, 2006

For comfort cooling applications, standard design practice uses the concept of 'design day' — conditions that are exceeded, on average, on ten days per year. On these ten days, it is expected that the HVAC system will be fully loaded (but at higher efficiency than at part-load). Cooling systems can also operate fully loaded when removing heat built up after a hot weekend. However, these situations are eased somewhat by the diversity that is likely to occur in other loads, such as occupancy and equipment (i.e. some people will be on leave or sick etc. and not every area will have its entire allocation of equipment installed or operating).

If a HVAC system is under-sized, there will be more hours per year when the plant is running fully loaded, and the system will not be able to hold indoor design conditions even on a 'design day', let alone any hotter days.

If a HVAC system is over-sized, it never runs fully loaded and a log of system loads may never reach 80% to 90%. An over-sized packaged plant may tend to short-cycle and is unlikely to control humidity well.

A survey of 50 HVAC systems in the UK showed that 80% of the heating plant, 88% of the ventilation plant and 100% of the chiller plant incorporated capacity above that needed to meet design requirements. Similarly, a case study from Hong Kong found that an original design included four 2,000 kW chillers (total 8,000 kW), but that operating records showed that the highest cooling load recorded was 3,516 kW.

Processes that lead to over-sizing

• High design guide values: Evidence suggests that high design guide values for estimating internal heat gains (occupancy, lighting and equipment) are one reason why commercial HVAC systems are being over-sized. These values are based on high occupancy levels (persons/m²), which are rarely reached. Some of the design guide values that may be over estimated include:
  • occupancy loads — traditionally, design loads for occupancy in office buildings are set at ten m²/person. However, most office buildings have ranges from 15 m² to 18 m².  Consequently, many offices may be designed for occupancies that are 50% to 100% larger than required
  • internal loads — the Property Council of Australia (PCA) grading matrix quotes internal load capability for a 'premium grade' building to be more than 25 W/m², with anecdotal reports of property managers advertising internal load capabilities of 40 W/m². In reality, for general open-plan office space, there seems to be evidence of the internal load reducing. This is due to uptake of much more efficient LCD monitors that also offer other advantages in glare and contrast performance. Many employers are providing employees with laptops, and requiring them to take them home. Both these actions tend to reduce internal loads, because the equipment is much more efficient and is not left on overnight. Reported measured loads from office equipment in 44 buildings in the US found the simple average was 8.9 W/m², with the highest value being 12 W/m². However, there is greater requirement for areas dedicated to IT that house servers and other high-power equipment in a confined space due to security requirements. These areas require 24-hour cooling and are usually conditioned by additional supplementary HVAC systems, supplied by a dedicated tenant condenser water system. These internal loads should not be accounted for in calculating the size of the base building chilled water system
  • temperature set-points — close control of internal temperatures, for example, 22.5 °C ±1 °C, is difficult to maintain in practice and can lead to excess capacity and higher energy use. The energy efficiency provisions in the new Section-J of the BCA require HVAC systems to be designed to maintain a temperature range between 20 °C and 24 °C for 98% of the system operating time. Such wider thermostat settings can improve stability of operation due to a larger 'dead-band' provision, and may also result in a smaller system capacity requirement.
• Discrete design process: Concept designs can be carried out independently by project team players. For example, an HVAC designer may use overly conservative glazing characteristics very early in the project and develop high cooling load estimates. If these are not revised further down the track, for whatever reason (e.g. paucity of time or budget), there is a good chance that the HVAC system will be over-sized. An interactive approach to design where all major energy sub-systems are reviewed together would lead to optimised façade, electric lighting and HVAC systems.
• Conservative design approach: A number of factors can be approached from a conservative stance. If these factors are independently added together, the result could be a system that is significantly over-sized. Some of these factors include:
  • overshadowing — not considering the impact of surrounding buildings when doing the cooling load calculations can have a significant impact on peak demand
  • unknown tenants — most buildings in Australia are speculative in nature. Tenant requirements are unknown until late in the project, when a real estate agent is successful in finding an anchor tenant
  • contractual obligations — a correctly designed system will not maintain temperatures during the worst hours of the year, when conditions go beyond the 'design day' and other internal loads are at high levels. Engineers are conscious of the fact that building use changes frequently, and design their HVAC systems to be able to cope with such changes by over-sizing.

Impacts of over-sizing
Over-sizing of HVAC plant has a flow-on effect through the project. Over-sized chillers will also require bigger pumps, pipes, cooling towers and valves, as well as a larger plant room. Chiller plant is usually available in discrete frame sizes. Over-sizing to a degree where the plant selection requires purchase of the next frame size can increase the absolute cost of the bigger chiller substantially, although the cost per kW may actually decrease.

Over-sized air-handling plant will also require larger fans, ducts and riser sizes. Over-sized HVAC systems in larger projects may also lead to poor thermal comfort in the conditioned spaces, as the plant may not be able to turn down enough to provide stable operation and may lead to poor air distribution, as cold air dumps from diffusers at low flows, instead of mixing at a high level with room air.

Over-sized equipment can also impose a penalty in terms of peak demand charges for electricity, as the larger motors draw higher currents when loaded. The impacts can flow through the energy supply chain, with thicker cables, larger switchboards and substations.

How to improve existing HVAC systems

Cooling may use as much as a third of the electricity consumed in a typical building. Heating systems use natural gas or oil as the primary fuel, but may also use electricity. Heating and cooling systems condition the air within a building so that occupants are comfortable. These systems consist mainly of chillers, boilers, cooling towers and pumps. Cooling systems generally have higher space conditioning capacities than heating systems, because a large portion of the building's heating requirements is supplied by waste heat from people, lighting and office equipment. The proper design and operation of these systems can translate into significant savings.

Cooling systems consist of various components that must work together to operate at highest efficiency, while ensuring proper occupant comfort. Improvements to any system must incorporate improvements to its individual pieces of equipment. However, these changes must be viewed as part of an integrated system approach. Modifications in the design or operation of one set of components to improve a building's overall efficiency will affect the operation of other equipment within the system.

There are four types of mechanical compression chillers — centrifugal, screw, scroll and reciprocating. Different applications call for different chiller types.

Alternative HVAC systems

Over the last few years, several alternative HVAC systems have come onto the market and have been incorporated into some of Australia's most energy-efficient commercial buildings (Claridge, 2006).

These systems include:

• chilled beams
• gas-fired systems
• ice and chilled water storage (See the articles on Charles Darwin University (Northern Territory) and William McCormack Place (Queensland) for examples)
• air and/or water heat recovery
• high-efficiency compressors
• variable speed drives
• control systems
• high-efficiency motors
• underfloor air-conditioning (see snapshot case study on Bendigo Bank)
• BATISO (see snapshot case study on Kangan Batman TAFE)
• Shaw method of air-conditioning
• hybrid water coolers (See the articles on Royal Melbourne Hospital and Brisbane's Central Plaza for examples)
• magnetic bearing chillers (See the articles on Melbourne's AXA for example).

Advanced GHP
Advanced GHP is a gas-engine driven multi-indoor unit climate control system. This system is used at 40 Albert Road and is proposed for the refurbishment of the Grand United Building in Sydney's CBD. The advanced GHP incorporates a sophisticated control system that allows the condition of each space to be individually set, as well as a variable speed compressor that adjusts to the demands of the building.

Co-generation with an absorption chiller
33 Bligh Street in Sydney has 100% stand-by power provided by a 1,500 kVA diesel generator, complete with underground fuel storage and a gas-engine generator. Also, instead of an electric-powered chiller, the building uses a 1,080 kWR Li-Br (lithium bromide) absorption chiller (Claridge, 2006).

In periods of peak demand, the cooling load on the absorption chiller signals the generator to fire, meaning that the total electrical load of the building is met by stand-by power during extreme weather conditions. This is equivalent to as much as 1,750 kVA in peak demand reduction. At other times, a conventional electric HVAC system operates.

With a reciprocating engine, heat is recovered from the engine's jacket cooling water, lubricating oil circuits and exhaust through heat exchangers. An absorption chiller uses heat (instead of a compressor) to maintain the pressure differences in the refrigerant circuit. The refrigerant is circulated from the evaporator through an absorber, where it absorbs a lithium bromide solution, to a concentrator where the refrigerant is evaporated out of the solution. This is cooled in the condenser and expanded into the evaporator again to chill the secondary heat transfer medium. With few moving parts, an absorption chiller requires minimal maintenance.

Pre-conditioning
The summer peak demand from HVAC systems, in particular the primary refrigeration plant, is due to the need to condition extremely hot and/or humid outside air in systems designed for relatively cooler and drier normal summer conditions (Claridge, 2006). Electrical demand from the primary plant can be reduced by pre-conditioning the outside air (i.e. reducing heat and moisture levels before the air flows over the conventional cooling coil). This lets the cooling coil do what it is designed to do, thereby reducing total HVAC system demand during the critical peak period. Pre-conditioning units can be retrofitted to reduce peak demand or fitted to new systems where they reduce the overall size of the HVAC system needed for the task.

Pre-conditioners may remove sensible heat (pre-cool) or latent heat (dehumidify) or both. Some technologies reduce the electrical load further by recovering waste energy from the exhaust air and using this to reduce humidity. The key principles in pre-conditioning are:

• evaporative cooling — this lowers the dry bulb temperature of air by bringing it in close contact with water. The heat in the air evaporates the water, which involves a change of phase from liquid to vapour. Evaporative coolers may be associated with problems of corrosion and contamination. Indirect evaporative cooling uses water sprays to cool the exhaust air, which is then used to cool the ventilation air through an air-to-air heat exchanger. By spraying the exhaust air rather than the ventilation air, there is less risk of contamination. Evaporative pre-cooling of ventilation air removes only sensible heat. Therefore, it is most effective in hot, dry conditions. With indirect evaporative cooling, heat from the heat exchanger can be used to dehumidify as well as cool the outside air
• air-to-air heat recovery — this can lower both temperature and humidity by transferring the heat and moisture between the ventilation and exhaust airstreams. The effectiveness of air-to-air recovery systems varies across applications; however, they usually lower the load on primary refrigeration plant and increase the load on fan motors. Heat recovery units need larger fans because they cause a loss of pressure in both ventilation and exhaust airstreams.

The most common recovery unit is the rotary energy wheel regenerator (also called heat wheel or enthalpy wheel). A desiccant film coating on the surface of the wheel absorbs moisture from the outside air as it passes through one side of the wheel, then carries the moisture until it meets the less humid exhaust airstream where it 'desorbs'.

The desiccant is a hygroscopic chemical (i.e. it attracts and absorbs moisture from the air). Desiccants need heat to regenerate (i.e. reduce the moisture they absorb). There are three types of desiccant dehumidifying systems:

• solid desiccant on a rotating wheel
• liquid desiccant in a direct open circuit
• liquid desiccant in a dual indirect closed circuit.

The key parameters of these systems are their efficiency in removing sensible and latent heat, and the degree to which they are prone to contamination and corrosion (Claridge, 2006).

Heat wheels use a silica gel to absorb moisture from the outside air. They produce a drier, but warmer, ventilation air and need a heat exchanger to cool the ventilation air. They also need heat to regenerate the desiccant and are particularly suited to applications with waste heat. Heat wheels can lead to contamination from the desiccant (it needs to contact the humid air to do its work) and are prone to cross-contamination between the airstreams.

Contamination is also an issue for units in which a liquid desiccant, usually lithium chloride, removes moisture directly from the ventilation air in an open circuit. The health effects of inhaling desiccants are not well known. This risk is reduced in a dual indirect closed circuit where the desiccant is used to remove moisture from the exhaust airstream, and a combination of indirect evaporative cooling and air-to-air heat exchange is used to cool and dry the outside air.

Taking control
The importance of a properly functioning control system cannot be overstated. According to AIRAH, 'poorly designed, badly commissioned and improperly maintained automatic controls are undoubtedly the greatest cause of wasted energy in many air-conditioning systems. Very often simultaneous requirements for heating and cooling can be incorrectly perceived by controls that have deviated from their set-point' (Penny, 2004). Direct digital control is becoming the standard.

Variable speed drives (VSD)
The advantage gained in both productivity improvements and reduced energy consumption by using AC variable speed drives (VSD) on pumps, fans, compressors and other equipment has been widely documented in the past few years (Sustainability Victoria, 2006a). Variable speed drives can reduce energy costs and prolong the life of equipment by adjusting motor speeds to meet load requirements. For example, by lowering fan or pump speed by 15%-20%, shaft power can be reduced by as much as 30%.

There are many advantages to variable speed drives over other forms of control. These include the following:

• Energy is saved by replacing mechanical fluid flow controllers with integrated motor speed control. Generally, these energy savings translate into cost savings and a reduction in greenhouse gas emissions for a given level of production.
• The soft start characteristic of VSDs eliminates voltage dips and reduces starting shock on motor, couplings, gears and driven equipment, in turn reducing maintenance.
• Running at reduced speed reduces wear on all drive train components and reduces the need for high maintenance items such as dampers, throttling valves etc.
• The range of flow control is generally higher with VSDs compared to mechanical controllers, and the likelihood of surges and vibration is reduced.
• Operating speeds in excess of 3,000 rpm for 2-pole AC motors are possible without the use of gearing.

Available motors range from 0.75 kW to 500 kW, depending on their cost and ability to perform under extreme conditions. This, combined with continuing advances in power electronics and microprocessor technology, allows AC variable speed drive designers to incorporate greater control and greater power handling capability, and to reduce switching losses. As a result, variable speed drives now have:

• increased drive efficiency (typically 97%-98%)
• reduced volume and weight
• lower price (e.g. 55 kW VSD unit with filters costs ~$18,000 installed)
• reduced audible noise level
• improved power factor
• reduced harmonic distortion to supply
• improved reliability
• larger voltage and current rating
• high switching speeds and lower losses.

Improved COPs (coefficient of performance)
To a greater or lesser extent, most of the innovative technologies available to reduce peak demand also improve equipment and/or system COPs. For example, whenever the cooling load is reduced, the COP of the refrigeration plant is improved. Similarly, motors with variable speed drives have higher COPs. This can also be achieved by replacing key equipment, such as the chiller, with a more efficient unit. Likewise, power factor correction can also improve appliance COPs. However, for effective demand reduction, the system COP also has to be improved.

The focus here is on two technologies; one that can significantly improve the system COPs of conventional systems, and one that uses a different approach altogether.

Chilled beams
Chilled beams take advantage of the fact that hot air rises. The beams circulate chilled water through elements mounted on the ceiling. By circulating higher temperature water at 16 °C (assuming this is above the room dew point), compared to 6 °C in a conventional system, chilled beam systems use smaller chillers and do not need to reheat. By using fans only to circulate fresh air, they use smaller fan motors. This translates into lower demand, especially in summer peak conditions. As people, their equipment and their activities generate heat the warm air rises to the ceiling, where it circulates around the beam. As it cools, the air falls. The radiant cooling from the beams supports the process. 'Active' chilled beams use fans to push the air around the beams; 'passive' chilled beams let the air circulate around the beams naturally. In both systems, 100% fresh air is introduced into the space separately via mechanical fans. If the outside air is very humid, it may create condensation on the beams. Therefore, a dehumidifier is often added to the system.

Kangan Batman TAFE     The Kangan Batman TAFE Automotive Centre of Excellence (ACE) is the first dedicated automotive training facility in the southern hemisphere. The building itself is also unique in the way innovative sustainable design features have been integrated. In an Australian first, BATISO active mass cooling and night sky cooling systems have been combined in a single building. These and other design measures, such as chilled beams, thermal chimneys and natural ventilation, mean that the building's operational energy demand for ventilation and air-conditioning will be reduced by 68% compared to average Melbourne office buildings.   The BATISO system uses hydronic pipes embedded in concrete floor slabs of the building structure. These can be used for cooling or heating by pumping warm or cool water through the pipes. Cooling will be the main demand in the ACE, so the pipes are installed in the floor slab above the space to radiate cool air downwards. This maximises the efficiency of the cooling process. BATISO piping coils in concrete slab Source: AIRAH, 2005a     The thermal mass of the slab provides comfortable radiant heat exchange to the space below. It also saves costs by reducing the size of cooling plant and mechanical reticulation required, and substantially cuts energy consumption and operating costs. The extensive use of radiant cooling allows equivalent thermal comfort to be achieved at higher internal temperatures.   Source: AIRAH, 2005a

30 The Bond   30 The Bond at Hickson Road, Millers Point, is a $112 million nine-storey building owned by Deutsche Office Trust and was the first large-scale commercial building in Australia to use chilled beams.   Chilled beams operate by pumping chilled water through cooling elements in the ceiling. People, computers and office equipment heat the air, which rises to the ceiling. This air is then cooled by the chilled beams and falls, creating a natural convection process of hot air rising and cold air falling.   Additional radiant cooling from the chilled beams supports the convection process. In addition to the chilled beams, fresh air is continually provided to the workplace and exhausted from the building without being re-circulated. This significantly increases the quality of air within the office space and reduces the risk of sick building syndrome.   The implementation of chilled beam technology enables the overall reduction of the building's height by up to one metre below the established maximum building envelope, as large-scale, roof top heating and cooling equipment is not needed. This improves views and access to light for neighbouring apartments, as well as making the roof top garden possible.

Bendigo Bank, Bendigo   Aiming to become the first new 5-star Green Star commercial building in regional Victoria, the new Bendigo Bank head office — a six-story office building set on an entire city block in central Bendigo, Victoria — has been designed to cut greenhouse gas emissions by 820 tonnes per year and to reduce energy consumption by 60%.   One of the major features of this project is the implementation of an underfloor air-conditioning system, which circulates tempered air (T >= 19 °C) to user-adjustable floor vents at the office workstations.   Achieving positive displacement, the air, via the swirl effect of the floor outlets, flows at low level and rises up at points of heat source (such as people and equipment), aiding in the natural rise of the lighter hot air, and replacing the warmer rising air with the filtered, tempered air with minimal turbulence.   The combination of higher supply air temperature and volume, lower pressure losses for air delivery within the floor void area, the delivery through the outlets at low velocity, and the use of stratification translates to lower energy costs and higher operational efficiency.   As part of the Bendigo Bank's brief to create an ideal working environment for the 1,000 staff members to be located in the building, individual users will be afforded significant control over the indoor environment of their workspace.   Source: McGowen, 2006

Green Square South Tower, Brisbane   Green Square South Tower (Brisbane) is the first commercial building project in Australia to use the high efficiency Carrier Aquaforce Chiller units that utilise micro-channel gear exchangers and high efficiency rotor compressor units. These units not only offer higher energy efficiency but also come with the additional benefit of 30% less refrigerant than conventional chillers. Carrier Aquaforce Chiller Source: Leighton Contractors

Links:
AIRAH — maintenance for energy efficiency
Australian Greenhouse Office — variable speed drives
Center for the Built Environment (US) — mixed mode systems
CRC Construction Innovation — right sizing air-conditioning systems
Kangan Batman TAFE — Automotive Centre of Excellence (ACE)

Lighting opportunities

• Use of natural lighting
• How to select the right system
• Replacing or upgrading existing systems
  

Use of natural lighting

Source: Altomonte, 2004

In a work environment, a combination of daylight and artificial light is preferable, in order to produce sufficient and suitable lighting for tasks throughout the room, both day and night. Good integration between these two sources of light makes it possible to gradually dim the amount of electric light when available daylight is sufficient for the task.

The design of an office lighting system should also provide for the various requirements of its occupants, allowing users flexibility and personal over-ride to adjust (at least partially) the luminous environment according to their individual needs. Privacy and personal needs require that each area be separate from other workstations in terms of the luminous environment, and that workstations can be fitted out in a personalised way. Depending on the different tasks and activities performed in a space, several adjustable lighting systems are preferable to evenly distributed ceiling lights. In terms of light distribution, a combination of diffuse and direct light — with directional lighting and some diffuse light needed to avoid dark areas with dense shadows — can assist in the perception of three dimensional objects and give 'life' to an environment.

In an office, daylight can provide adequate ambient light for most working hours, and when supplementary light is needed, user-controlled task lights can ensure work requirements are met.
Ambient illumination should be significantly lower than task requirements. Likewise, different artificial light is required during the day than at night, when, as a general rule, light should be calming and restful, in sync with the human biorhythm.

In a day-lit space, it is obvious that people close to windows will often use natural light as their primary illumination source. For other locations, direct and indirect lighting should be designed to pair with daylight distribution. To ensure adequate illumination, fixtures and lighting circuits should preferably be grouped by areas of similar daylight availability (e.g. in rows parallel to window wall), in order to allow the possibility for control to be added during retrofit.

How to select the right system

Most buildings require several types of lighting: ambient lighting for basic illumination of the space; task lighting, which enables users to control additional light they may require at their workspace; architectural lighting to convey a particular mood or feeling (e.g. in a corridor or lobby); and display lighting to highlight particular features in the space (e.g. merchandise in a store, a painting in an office or museum, or a chalkboard in a schoolroom). The information below provides some guidelines for making efficient choices for a range of lighting applications. However, to maximise the efficiency of the lighting system, it is important to consider the primary use of the space, the extent to which the lighting system can take advantage of natural lighting, and the degree to which task lighting can supplant general illumination. If possible, a professional lighting designer or supplier, whose design background and attention to efficiency are established, should be employed to assist with creating an efficient lighting system.

Ambient lighting
Ambient lighting provides general illumination of a space. General lighting designs were originally intended to serve the primary lighting needs for office typing pools. With the advent of modular office furniture, general lighting designs were no longer practical. The furniture shadowed the light, and new equipment (computers) imposed new demands. In response, lighting designers shifted towards a system that combines lower ambient light levels with task lighting. As a result, instead of providing 100% of light for the space, it is now recommended that ambient lighting be designed to provide about 30% of the lighting needs, with the rest of work-oriented lighting provided by natural light and task lighting.

In general, nearly optimal results can be achieved by using new 'super' or 'premium' T8 or T5 fluorescent lamps with electronic ballasts for low-ceilinged spaces, and HID or high-intensity T5 lamps for spaces with higher ceilings.

Down lighting
Downlights are used for general illumination in many residential and commercial applications, especially in lobbies, halls, corridors, stores and other finished spaces. Downlights can be equipped with incandescent, halogen, low voltage, compact fluorescent, or HID lamps. Compact fluorescent and HID lamps should generally be selected, using a rule of thumb of one watt for every three watts of incandescent or halogen lamp that would normally be used (New Building Institute, 2003).

• For most applications, consider vertical lamp and dual horizontal lamp compact fluorescent downlights.
• For applications requiring high-wattage incandescent or halogen lamps, consider metal halide downlights, especially with the new high colour quality ceramic metal halide lamps.
• If the above options are not appropriate, consider retrofitting existing cans to use CFLs. Retrofit kits generally work better and save money over the long run, but screw-in retrofits provide lower first cost and are often acceptable in performance and aesthetics, particularly in low-ceilinged spaces.
• Failing all of the above, consider replacing incandescent reflector lamps with lower wattage halogen or energy-saving incandescent lamps.

Task lighting

Shifting from older general lighting systems to an approach based on lower ambient light levels, with a task lighting complement, introduces energy saving opportunities by allowing some degree of occupant control over lighting levels. Research shows that individual preferences for lighting levels vary widely and that allowing individuals some control over their own lighting not only increases user satisfaction and productivity, but also results in measurable energy savings. Task lighting also makes it easier to adapt the lighting in a space as end-uses or occupants change.

Many types and configurations of task lighting are available to meet user preferences and needs, including under-cabinet lights, table lamps and floor lamps. Task lighting typically uses a fluorescent or compact fluorescent source. Improvements in CFL technology have made dimmable lamps increasingly common and some specialised fixtures are taking advantage of these developments (New Building Institute, 2003).

Architectural lighting
CFLs or metal halide lamps for down lighting, wall washing, wall sconces and pendant fixtures can be used for architectural effects, while larger fluorescent lamps can also be used for wall washing. Advancements in metal halide technology have produced ceramic metal halide lamps with improved colour rendering characteristics. The use of ceramic arc tubes in metal halide lamps provides the warm tones desired in retail applications and the concentrated beams required for accent lighting in retail and other architectural applications. Furthermore, these lamps represent an attractive alternative to the halogen PAR lamps commonly used in these applications, as they have a much longer life and use just half of the energy (see Table 10). All major lamp manufacturers offer ceramic metal halide spot lamps (New Building Institute, 2003).

Retail display lighting
Track lights are the most common display lighting systems. Track lighting consists of electrified track to which lamp holders (sometimes called track fixtures or 'heads') are attached. Track lighting was developed to offer flexibility for display lighting in stores and museums. It has become a popular way to incorporate display lighting in many building types. Unfortunately, track lighting enables (and often encourages) the use of too much incandescent or halogen lighting.

Large area lighting — indoors and out
For large areas, metal halide lamps should be used if colour discrimination is important. If colour discrimination is not important, high-pressure sodium lamps can be used. Electrodeless lamps, which are becoming more available, are appropriate in outdoor applications and in hard-to-reach indoor and outdoor situations, such as in malls with high ceilings or for security lighting. Their primary disadvantage is that they are expensive, although they do offer long life, which reduces replacement and maintenance costs (New Building Institute, 2003).

Utility and service areas
In utility and service areas, fluorescent lamps, CFLs, or HID lamps should be used, as appropriate. Where small utility or service areas are occupied intermittently, incandescent lamps or CFLs on timer switches are often the best choices, while occupancy sensors are another option for all but mechanical rooms. HID lamps are not suitable for service areas in which the lights must come on quickly. T5 high-output lamps can be used in place of HID lamps, since they are totally dimmable and controllable, provide greater energy savings and improved colour characteristics, and last longer (New Building Institute, 2003).

Exit signs

Exit signs use a surprising amount of energy. Many exit signs employ incandescent lamps, typically consuming 30-40 watts per unit. These lamps are designed principally for long life (they generally last 20,000-40,000 hours), but efficiency is compromised in the process. A typical exit sign of this type consumes around 350 kWh of energy per year.

In the 1980s, many exit signs were retrofitted with CFLs to save energy. At this point, however, LED exit signs are rapidly becoming the new standard. A typical LED exit sign consumes less than three watts per face. LEDs have a very long life (at least 50,000 hours), which reduces maintenance costs and provides even illumination. Recent developments in green LEDs make both red and green signs available and cost-effective. Existing incandescent exit signs can be replaced or retrofitted with LED adapters.

Comparison of various lighting technologies

Lighting technology	Annual energy use	Annual energy cost	Lamp service life	Annual CO2 emissions
LED	44 kWh	$6.60	10+ years	36 kg
Fluorescent/CFL	140 kWh	$21.00	10.8 months	115 kg
Incandescent	350 kWh	$52.50	2.8 months	287 kg

Savings per unit may be small (table above), but as a large commercial building may contain 500 exit signs, the annual cost of incandescent lights would be $26,250, while LED-based signs would only cost $3,300 per annum. Switching to LED exit signs would therefore represent an annual saving of $22,950 (Energy Star (US), 2005).

Another option is non-electrical photo-luminescent exit signs. These are typically a metal faceplate with letters and symbols stencilled in a non-toxic, non-radioactive compound of strontium oxide aluminates. The strontium compound letters and symbols store ambient light energy during normal conditions, and then when the light is extinguished (i.e. in an emergency), the letters glow brightly as the compound releases the stored energy as an intense green-yellow colour. This is the same 'glow-in-the-dark' technology used in toys and other curios, but with a radiance that is much brighter and longer-lasting (O'Connell, 2006).

Replacing or upgrading existing systems

The lighting systems within a building are an integral part of a comfortable working environment. Over the course of their life, all lighting systems become gradually less efficient. Certain efficiency losses are unavoidable, such as reduction in light output, which is due to the aging of lighting equipment. However, other efficiency losses, such as improperly functioning controls, dirt accumulation on fixture lenses and housings, and lamp lumen depreciation, can be avoided by regularly scheduled lighting maintenance.

Insufficient lighting can have a negative impact on energy performance of the building. When building lighting is inadequate, occupants may bring in less efficient fixtures, thus increasing the lighting and cooling loads in the building.

Upgrading lighting systems is an easy way to save energy. As lighting accounts for up to 40% of energy costs in commercial buildings, significant financial savings can be made. Lighting levels are designed for maintained illuminance, which ensures that the average lighting level will at no time fall below that recommended by Australian Standard 1680. Without reducing performance and visual satisfaction, significant savings in energy consumption and capital costs can be achieved by applying an effective design and operating approach to a lighting system.

Lighting tune-up
A lighting system tune-up should be performed in the following order:

1. Follow a strategic lighting maintenance plan of scheduled group re-lamping and fixture cleaning
2. Measure and ensure proper light levels
3. Calibrate lighting controls

Periodically cleaning the existing fixtures and replacing burned-out lamps and ballasts can considerably increase fixture light output. This simple and cost-effective tune-up item can restore light levels in a building close to their initial design specifications.

After the fixtures have been cleaned and group re-lamping has taken place, the next step is to measure existing light levels to ensure that proper illuminance levels are provided for the tasks being performed in the space. As space use and furnishings may change over time, it is important to match the lighting level to the current occupant requirements. The Illuminating Engineering Society of North America issues recommended illuminance levels depending on the job or activity performed. Over-lit or under-lit areas should be corrected. Lighting uniformity should also be assessed, as relocation of furniture and walls may have altered lighting distribution.

Once the proper light levels and uniformity have been achieved in a space, the automatic lighting controls should be examined. Many buildings use a variety of automatic controls for time-based, occupancy-based, and lighting level-based strategies. These controls may not have been properly calibrated during installation or may have been subsequently tampered with by occupants. Adjusting these controls and associated sensors during the tune-up will reduce occupant complaints, maintain safety, and ensure maximum energy savings.

Many buildings utilise energy management systems, time clocks, and electronic wall box timers to control lighting automatically, based on a predictable time schedule. These systems need to be programmed correctly to ensure that lights are only operating when the building is occupied, and that over-rides are operational where required. Exterior lighting schedules must also be changed throughout the year, according to the season.

The performance of occupancy or motion sensors depends on customising the sensitivity and time-delay settings to the requirements of each individual space. The sensor's installed position should also be checked to ensure adequate coverage of the occupied area. Furnishings should be kept from obstructing the sensor's line of sight.

Any indoor and outdoor photocells should also be checked during the tune-up to ensure that the desired daylight dimming or daylight switching responses are being met. Set-points should be adjusted so that the desired light levels are maintained. Photocells and dimming ballasts are also used to save energy in non-daylight areas through lumen maintenance control, a strategy to adjust system output to compensate for aging lamps and dirt accumulation on luminaires. To maintain continued energy savings in lumen maintenance control strategies, the set-point will need to be tuned manually to reduce the light level by 25%-30% (the expected light level depreciation over the maintenance cycle) each time fixtures are periodically cleaned and re-lamped. This will allow the ballast to increase the system output over time to maintain the illuminance set-point.

Savings
Although the savings associated with performing a lighting tune-up will vary depending on the quality and performance of the current lighting system, they can be significant. For example, cleaning alone may boost fixture light output from 10% (in enclosed fixtures in clean environments) to more than 60% (in open fixtures located in dirty areas). Simple calibration of occupancy sensors and photocells can restore correct operation, reducing the energy used by the lighting system in those areas by 50% or more.

Retravision, Auburn     Australia's first pilot lighting energy efficiency program within a retail environment at Auburn Retravision has reduced energy consumption by almost 50%, and as a result will significantly reduce annual lighting costs for the business. It will also reduce heat loads associated with lighting by a massive 75% a year. As a consequence, electricity costs at Auburn Retravision will reduce by some $10,000 a year. Auburn Retravision is a medium-sized homemaker/bulky goods style retail environment of approximately 1,400 m2.   In Australia, lighting generates almost 25 million tonnes of greenhouse emissions each year and costs the community over $2 billion in electricity. Lighting Council Australia, with assistance from the Australian Greenhouse Office, undertook a complete refit of Auburn Retravision's lighting to find an energy-saving solution for small business, and to significantly reduce both energy consumption and greenhouse gases from lighting energy use.   'The results from the pilot program at Auburn Retravision are outstanding. Our aim was to demonstrate significant savings in a commercial environment using current affordable lighting technologies. We have doubled our initial savings targets', said David Tilbury, Chairman of Lighting Council Australia.   'This outcome clearly demonstrates the benefits of adopting a professional approach to the utilisation of quality lighting products and technology', Mr Tilbury said.   In the initial stages, the project identified a number of qualitative and quantitative elements that had to be addressed to attain a minimum 20% reduction in energy consumption. The original design included use of a large quantity of high wattage lamps, upward lighting, overlapping of fluorescent lights, and poor use of colour rendition.   The redesign of the Auburn Retravision presented the retail space in four visually distinct spaces or 'rooms', which allowed shoppers to be drawn into the different areas with the use of differing light fittings, colour temperatures and sources. Each space was designed and fitted with lighting specific to its needs, while at the same time offering visual interest.   Auburn Retravision co-owner, Julie Rowland, was delighted with the result. 'We are ecstatic about the new look of the store. Not only will the savings be good for the environment but they will also have a positive impact on our bottom line', she said.   Source: Lighting Council of Australia (2006)

Dumas House, Perth   At Dumas House, illumination of office space was a major consumer of power, so Jones Lang LaSalle, on behalf of the Department of Housing and Works, undertook an extensive lighting upgrade. With 14 floors of offices to consider, the upgrade was done in stages and one level was chosen to provide a benchmark for the rest of the building.   Twin standard fluorescent lamps were replaced with single triphosphor lamps and diffusers. On just one floor, a saving of 36,500 kWh and $4,500 per annum was achieved, which equated to a less than five year payback period on the $22,000 outlay needed to complete the changes.   Three floors had occupancy sensors fitted in common areas, such as pantries, lobbies and toilets, for after-hours control. Default times were set to 7am-7pm, 5 days a week and a PIN and keypad system was installed to enable tenants to illuminate work areas after hours. This initiative has more than halved lighting energy consumption, with a 25,000 kWh annual saving in power and a $3,100 annual saving in costs.   A full lighting upgrade was then undertaken on all floors and the existing twin fluorescent lamps were replaced with a single triphosphor lamp, starter and prismatic diffuser. Keypad control of lighting in tenant areas was also included. At a cost of just over $130,000, the exercise has produced impressive savings. Electricity use is down by 510,000 kWh, which equates to a $63,000 a year reduction in energy costs. It took only two years to gain a full return on the capital outlay.   Source: Sustainable Energy Development Office, 2006

AGO, Canberra   Located in a basement beneath an existing ground-level car park on the site of the John Gorton Building, this innovative project entails a refurbishment of the basement into new office spaces, providing daylight and visual access to the outside environment via a series of courtyards and skylights. The subterranean nature of this project highlights the necessity of a well-considered approach to natural and artificial lighting strategies.   Daylighting Four courtyards and six skylights are distributed strategically across the building plan, bringing natural light into the space and significantly reducing the demand for artificial lighting. Light shelves assist in reflecting daylight further into the building, diffusing concentrated lux levels occurring around the courtyards and skylights to provide more uniform lighting conditions. Daylight sensors adjust artificial lighting levels according to available natural light, thus minimising energy use.   Artificial lighting Suspended luminaires consist of three energy-efficient T5 fluorescent lamps with dimmable ballasts. Two lamps provide upward ambient lighting, and the remaining lamp provides downward task lighting. Each component is individually controlled to coordinate with daylight conditions from the skylights and courtyards, and to optimise energy savings.   Lighting control A Clipsal 'C' Bus system controls lighting via movement sensors, local area controls, and a series of lighting level sensors at ceiling and desk top height. All artificial lighting responds to the levels of natural light within the occupied space. Local switches control designated work areas, to provide flexibility in the zoning and use of lighting. Movement sensors are incorporated into many aspects of the design, including the program for the beginning and end of the day, and occasionally occupied spaces, such as bathrooms.

Links:
Lighting Council
Lighting Innovation Centre

Appliance opportunities

• Selecting the right appliances
• Computers and monitors
• Photocopiers
  

Selecting the right appliances

Some simple guides to selecting energy-efficient appliances include:

• Where possible, ensure that equipment conforms to Energy Star requirements. Specifying the requirement of Energy Star compliant and enabled office equipment in purchasing policies and procurement contracts ensures that your supplier delivers all products with the Energy Star low-power features enabled and tested.
• Check power ratings in operating, low power, sleep and off modes so that you can select the most energy-efficient, value-for-money model that meets all your operating requirements. Bear in mind that some equipment can still consume energy after the on/off button has been switched off if the power-point is still switched on.
• Obtain data on the time the equipment takes to return to operation when it is switched on or woken up, so that you can select equipment that responds quickly. There is no definite correlation between energy use in sleep mode and speed of wake-up.
• Look for the lowest possible time options to move to low power, sleep and off modes. This will save you both energy and money (Sustainable Solutions, 2003).

Energy use and energy-saving opportunities of appliances

Type of  equipment	Significance	Energy-saving opportunities	Options for action
Personal computers	High: around 20% of office equipment (OE) energy	Wide range of energy use, from 10--90W Energy saving strategies: — high efficiency power supply — improved power management — efficient devices (e.g. processors) — laptops	MEPS for power supplies, power management and device efficiency; mandatory energy consumption disclosure or energy labels; government procurement programs
Monitors	High: over 20% of OE energy	LCDs with efficient power supplies offer up to 70% savings and further improvements are likely	Mandatory energy consumption disclosure; energy labels; MEPS; government procurement
Servers	Moderate--high; over 10% of OE energy + inefficient a/c systems	Energy saving strategies: — high efficiency power supplies — power management — efficient devices — air-conditioning efficiency	MEPS; mandatory energy consumption disclosure; government procurement; demonstrations and info programs for air-conditioning efficiency
Uninterruptible power supplies	Moderate: about 6% of OE energy	Key issue is to ensure the superior technology option is used, and that appropriate sizing (or high efficiency at low load) is achieved	MEPS; government procurement programs
Copiers and MFDs	Moderate--high: about 10% of OE energy	Likely that manufacturers will include various low power modes, and peripherals can use significant energy. Power management and reduction in copying/fusing energy are key issues. IEA Copier of the Future program shows substantial scope for improvement.	MEPS; mandatory energy consumption disclosure; government procurement; maybe energy labels
Printers	Moderate: about 6% of OE energy	Wide variation in energy use, especially between laser and inkjet, where up to 10-fold differences can exist. For laser printers, savings options are similar to those for copiers.	As for copiers, with energy labels for smaller equipment
Faxes and scanners	Moderate: probably <5% of OE energy	For inkjet models of faxes, stand-by is the major issue, but for laser faxes, total energy use should be considered. For scanners, automatic low power stand-by mode is critical	One watt programs; MEPS
Computer projectors	Small	Ongoing potential for improvement in efficiencies of lamp, fan, electronics and power supplies. Could rate on basis of energy use/light output plus performance of 'smart' energy saving features	Mandatory standardised energy use and light output disclosure; maybe energy labels
Hubs	Small	Power management and stand-by energy use probably the major issues. Could be rated by class based on capability	MEPS

Source: Sustainable Solutions, (2003)

Computers and monitors

When selecting computers and monitors, follow the general principles for buying green office equipment set out in 'Selecting the right appliances'. You should also:

• consider buying a laptop, since a laptop is much more energy- and materials-efficient than a desktop computer and monitor
• replace CRT monitors with LCD-type flat screens for desktop computers, as they are more energy- and space-efficient than standard monitors
• buy computers that have been tested with your network software, if applicable.

When using computers and monitors, you should:

• manually switch them off outside working hours, or consider installing EMO software to switch computers off automatically
• switch off the monitor if a computer is being used as a server and the monitor is not required
• switch off your computer whenever you are away from your desk for an hour or more or for whatever shorter time you find convenient
• experiment with your power management time settings to find the shortest convenient times that suit you.

EMO
If Energy Star settings cannot be enabled on equipment, an alternative energy-saving software product called Energy Management Option (EMO) is now available. This software can switch off computers when they're not being used and shut them down at night. It also provides calculations on energy, cost and greenhouse gas emission savings, which are useful details to include in a business's energy audits and reports.

EMO offers significant energy savings for the approximately one-third of all computers that are left on unnecessarily when not in use. If EMO finds that a computer has been inactive for a certain time, it saves all open data files, closes all applications and the operating system, and then switches the computer off. It provides users with positive feedback via an on-screen log-on of the amount of energy, dollars and greenhouse emissions that have been saved during the previous day and since the installation of the software.

EMO was trialled in the Australian Greenhouse Office and has been implemented throughout Environment Australia and the Department of Industry, Science and Resources. It was found to provide a convenient, though not complete, range of power management functions for operating systems such as Windows NT4, which doesn't work well with Energy Star.

However, additional action is still required to send the monitor and CPU to sleep, or to power down the hard drive.

EMO can also be used in conjunction with Energy Star to ensure that computers and monitors are actually switched off after hours, rather than just sleeping.

Photocopiers

When selecting a photocopier, follow the general principles for buying green office equipment set out in 'Selecting the right appliances'. You should take note of the following:

• If you are looking for a copier with accessories, make sure that the quoted power rating in lower power mode includes the power consumed by accessories.
• Look for a copier with an 'energy save' button in addition to programmable power management features, so that users can put the machine into low power mode as soon as they finish copying.
• Choose a copier with a seven-day clock that allows you to program it to turn off when it isn't needed at the end of each work day and on weekends.
• Unless you are buying a small format photocopier, choose one with the capacity to reduce from A3 to A4.
• Select a photocopier with a high recycled material content and that makes use of recycled components.

Copiers that have earned the Energy Star rating 'sleep' or power down when not in use, and use 40% less electricity compared to standard models.

Energy Star high-speed copiers feature duplexing units that automatically make double-sided copies, reducing paper costs by about $60 a month. Using less paper also saves energy because it takes ten times more energy to manufacture a piece of paper than it does to copy an image onto it.

Energy Star requirements for standard copiers

Copier speed (copies per minute)	0 < cpm < 20	20 < cpm < 44	44 < cpm
Low-power mode (watts)	None	3.85 x cpm + 5	3.85 x cpm + 5
Low-power default time	NA	15 minutes	15 minutes
Recovery time (30 seconds)	NA	Yes	Recommended
Off mode (watts)	< 5	< 15	< 20
Off mode default time	< 30 minutes	< 60 minutes	< 90 minutes
Automatic duplex mode	No	Optional	Optional

Links:
Australian Greenhouse Office
Energy Allstars
Energyrating
Energy Star

Existing building opportunities

• Recommissioning
• Lighting
• Supplemental load reductions
• Fan system upgrades
• Heating and cooling system upgrades

Energy efficiency measures are not restricted to new buildings. The vast majority of savings that are possible through energy efficiency measures can be achieved in existing buildings through upgrades and retrofitting.

Energy-efficient investments should not be undertaken in a haphazard manner. In order to maximise the rate of return for energy-efficient investments, an integrated approach for building upgrades is required.

The left figure illustrates how heat and energy flow in a building. Heat is given off by lights, people, and other supplemental loads, such as office equipment, all of which require space cooling. Solar radiation and hot outside air temperatures can also impact on space cooling needs. Conversely, cold outside air temperatures create the need for heating. Even when it is cold outside, a building may still require some cooling to remove excess heat given off by lights, people and equipment.

A staged approach synthesises these building system interactions into a systematic method for planning upgrades that enables energy savings to be maximised. The stages are:

1. Recommissioning: Building equipment, systems, and maintenance procedures should be periodically examined in relation to their design, including controls, intent and current operational needs.
2. Lighting: Energy-efficient lighting systems and controls that improve light quality and reduce heat gain should be installed.
3. Supplemental load reductions: Energy Star-labelled office equipment should be purchased, window films installed, and insulation or reflective roof coating added, to reduce energy consumption of supplemental load sources.
4. Fan systems upgrades: Fan systems should be properly sized, with variable speed drives added, and conversion to a variable air volume system should be considered.
5. Heating and cooling system upgrades: Chlorofluorocarbon chillers should be replaced, energy-efficient models should be retrofitted or installed to meet the building's reduced cooling loads, and boilers and other central plant systems should be upgraded to energy-efficient standards.

When the staged approach is performed sequentially, each stage includes changes that will affect the upgrades performed in subsequent stages, thus maximising energy and cost savings. The first three stages address reducing heating, cooling, and electrical loads. Once these loads are reduced, the HVAC equipment can be upgraded to meet the current loads and to optimise its performance. By implementing the load reduction strategies first, the savings from fans and HVAC systems will be greater, because these systems can be properly sized to handle the reduced loads.

Recommissioning

Source: US EPA, 2004

Recommissioning is essentially the same process as commissioning, but applied to the HVAC, control, and electrical systems of existing buildings. When standardised maintenance and energy management procedures fail to fix chronic building problems, recommissioning provides a systematic approach for discovering and solving them. Recommissioning entails the examination of actual building equipment systems operation and maintenance procedures, for comparison to intended or design operation and maintenance procedures.

The figure on heat flow in buildings above illustrates the interaction of all buildings systems and activities. Recommissioning capitalises on heating, cooling and electrical load reductions by continually monitoring energy consumption to optimise energy performance and savings.

Recommissioning can be a cost-effective retrofit in itself, sometimes generating more savings than the cost of the retrofit measure. This can result in additional savings other than direct energy cost reductions. For example, recommissioning may help avoid the need to install new or additional equipment, resulting in capital savings. In the recommissioning phase, numerous cost-effective strategies will need to be implemented to reduce heating, cooling and electrical loads, and overall energy consumption, while improving occupant comfort.

The best ways to save:

• Calibrate building controls such as thermostats and occupancy sensors
• Adjust operating schedules to ensure equipment is on only when necessary
• Check for leaking or improperly functioning steam traps
• Adhere to maintenance schedules

Take action!

• Recognise building tune-up as an opportunity to reduce energy costs and regain or improve comfort
• Allocate time and funding to a building tune-up separately from the ongoing maintenance budget
• Explore available financing options if in-house funds are not available
  
  

Lighting

Source: US EPA, 2004

Lighting consumes 25%-30% of energy in commercial buildings, and is a primary source of heat gain and waste heat. Excess heat and energy can be reduced by implementing an energy-efficient lighting system. Upgraded lighting systems can also improve lighting quality to increase occupant comfort and productivity.

Comprehensive lighting upgrades create opportunities to improve the efficiency of electrical distribution and HVAC systems by reducing these loads. The additional energy savings from lighting upgrades are discussed in subsequent stages of the upgrade process.

Benefits of a comprehensive lighting upgrade include:

• highly profitable energy savings and low-risk investment
• maximising energy saving opportunities for subsequent building systems upgrades
• increasing management and occupant acceptance of other energy-efficiency projects, if the lighting upgrade is successful.

The best ways to save:

• Design light quantity and quality for the task and occupants' needs
• Maximise lamp and ballast efficiency
• Maximise system efficiency, not just the components
• Use automatic controls to turn lights off or dim lights in day-lit spaces
• Establish a maintenance schedule for group re-lamping and fixture cleaning
• Use Energy Star-labelled exit signs
• Establish responsible disposal practices

Take action!

• Develop an implementation plan and budget for lighting upgrade projects
• Communicate project objectives and process to occupants
• Perform trial installations to assess light levels, occupants' acceptance, and energy use
  
  

Supplemental load reductions

Source: US EPA, 2004

Supplemental load sources are secondary load contributors to energy consumption in buildings. Some typical supplemental load sources are people, computers, lights and the building itself. These loads can adversely affect heating, cooling and electrical loads. However, the effect of supplemental loads can be controlled and reduced through strategic planning and the implementation of energy-efficient upgrades.

With careful analysis of these sources and their interaction with HVAC systems, the equipment size and cost associated with upgrades can be reduced. These upgrades can increase HVAC energy savings and reduce wasted energy.

Strategies to reduce supplemental loads include:

• reducing heating, cooling and electrical loads to allow the installation of smaller and lower first-cost HVAC equipment in fan systems and heating and cooling systems
• delaying (if possible) the installation of HVAC equipment until all loads are reduced and the impacts on HVAC systems can be measured directly
• taking the time to predict the magnitude of load reductions from upgrade projects (if the installation of HVAC equipment cannot be delayed).

The best ways to save:

• Ventilation upgrades
  • Control ventilation rates to meet minimum requirements
  • Install air side air economy cycle (depends on climate)
  • Utilise energy recovery equipment (i.e. heat pipes and heat wheels)
• Equipment upgrades
  • Purchase Energy Star-labelled office equipment and adhere to MEPS on air-conditioning etc.
• Building envelope upgrades
  • Install window films and/or shading
• Fill gaps to avoid infiltration
  • Install roof insulation

Take action!

• Assess supplemental load sources in the building to determine reduction opportunities
• Contact vendors, contractors, or an engineering consultant to specify upgrades for supplemental load sources
• Install energy-efficient upgrades to reduce the effect of supplemental load sources on heating, cooling and electrical systems
  
  

Fan system upgrades

Source: US EPA, 2004

Fan systems, also known as air-handling systems, are the conduit for getting conditioned air (heating and cooling) to people occupying a building, and therefore directly affect occupant comfort. Fan systems can be upgraded and adjusted to ensure air is delivered in the most energy-efficient way.

The figure on heat flow in buildings in buildings above illustrates how fan system upgrades can take advantage of the load reductions realised in other stages of an integrated approach to making a building more energy-efficient. The resultant opportunities for reducing the air-handling system's energy consumption are now tremendous. Continuing with the integrated approach can result in a 50%-85% reduction in fan power consumption.

Strategies for a fan systems upgrade include:

• rightsizing the cooling system to match reduced loads
• taking advantage of improvements in air-handling technology
• installing equipment that allows for more efficient operation, lower first cost, and lower maintenance costs.

The best ways to save:

• Fan system rightsizing
• Variable-speed drives
• Improved controls
• Energy-efficient motors
• Energy-efficient belts

If the purchase of replacement equipment is already planned, installing smaller components is less costly than replacing with larger equipment.

An easy target
The fans that move the heated and cooled air through a building constitute 4% of the total energy consumed by a typical commercial building. A US study found that almost 60% of building fan systems in the US were over-sized by at least 10%, with an average over-sizing of 60%. By rightsizing, an average of 50% in fan system energy can be saved. Moreover, these savings are independent of any other improvements, such as installing energy-efficient motors.

Heating and cooling system upgrades

Source: US EPA, 2004

Heating and cooling systems are the largest single consumers of energy in buildings. These systems condition the air within a building so that occupants are comfortable. Heating and cooling systems consist mainly of chillers, boilers, cooling towers and pumps. There are central heating and cooling systems, and unitary systems that combine heating and cooling. Opportunities exist for improvement to both central and unitary systems.

Strategies for upgrading heating and cooling systems include:

• measuring the heating and cooling loads
• rightsizing the heating and cooling systems
• replacing the chillers with new, more energy-efficient, non-chlorofluorocarbon (CFC) models
• upgrading the heating and cooling system components
• installing variable-speed drives (VSDs) on pumps and cooling tower fans
• optimising the operation of heating and cooling systems.

The best ways to save:

• Cooling system upgrades
  • High efficiency components
  • Cooling tower improvements
  • Free cooling
  • VSD pumping
  • Controls
• Heating system upgrades
  • High efficiency components
  • Controls

The conventional approach to upgrading a heating and cooling system is to address each component of the system individually. However, addressing the interaction between the components using an integrated system approach ultimately results in a more energy-efficient system. In addition, compared with assessing components individually, assessing upgrade opportunities for whole systems consumes less time and money in the long-term. Heating and cooling system components, particularly in central systems, interact with each other extensively. For example, chillers operate more efficiently if they receive cooler condenser water. Howe