An introduction to energy efficiency in commercial buildings

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This article introduces the definition of energy, the importance of energy efficiency and the sources of major impact.

Definition

• What is energy?
• How is it produced?
  • Electricity generation
  • Renewable electricity production
• Where is energy used?
  • Commercial building energy use
  • Office buildings
  • Hospitals
  • Retail

What is energy?

The most common energy sources used in commercial buildings are electricity and gas. Some buildings also rely on diesel fuel for stand-by generation, while solar electricity is increasingly used in new buildings.

Often, machines are used to convert energy from one form to another. The efficiency of a machine characterises how well it can perform such a conversion.

Energy may be converted so that it can be used by other machines, or to provide a service such as heat, light, or motion. For example, a solar cell converts solar radiation into electrical energy that can then be used to light a bulb or power a computer (Wikipedia, 2007).

Energy forms in buildings are dominated by electricity and natural gas. This energy is generally delivered from external sources, such as the electricity grid, but may also be sourced locally via energy generation systems, such as PV cells.

Links:
Wikipedia

How is it produced?

Overall, the fuel mix in Australia's domestic energy use has changed little in the past five years, although the share of consumption represented by natural gas and renewable energy continues to rise (ABARE, 2006). Commercial buildings also consume energy in the form of liquid fuels (such as diesel for generators), LPG and coal briquettes.

Electricity generation

The majority of Australia's electricity generation is sourced from large-scale fossil fuel fired power stations, and is delivered to consumers through an extensive national power grid.

Renewable electricity production

Almost 7.4% of Australia's electricity comes from renewable sources, with the majority of this coming from large-scale hydro-power stations located predominantly in Tasmania. Hydro-power accounts for 86% of renewable electricity generation, with the remaining renewable energy sources accounting for 1% of the nation's electricity generation (ABARE, 2007).

The Federal Government has set compulsory minimum renewable energy targets. The mandatory renewable energy target (MRET) imposes a legal obligation on electricity retailers and other large electricity customers to source an additional 2% of their electricity from renewable or specified waste-product energy sources by 2010.

Victoria and NSW have also introduced their own renewable energy target schemes.

Links:
ABARE
Office of the Renewable Energy Regulator (ORER)
Renewable Energy Generators of Australia (REGA)

Where is energy used?

Energy end-use in the commercial sector and residential sector has grown by 11% and 9% respectively since 1998-99 (Trewin, 2006).

Energy end-use, by sector

	1998-99	2002-03	2003-04
	PJ	PJ	PJ
Agriculture	68	106	95
Mining	267	296	314
Manufacturing	1,004	1,122	1,138
Construction	49	28	28
Transporta	1,217	1,207	1,251
Commercialb	212	236	235
Residentialc	386	413	421
Otherd	58	60	63
Total	3,261	3,467	3,545

a.        Includes all transport use, including household motor vehicle use.
b.        Includes wholesale and retail trade, communications, finance and insurance, property and business services, government administration and defence, education, health and community services, cultural and recreational services, and personal and other services, along with water, sewerage and drainage.
c.        Transport use by households is included in transport.
d.        Includes lubricants and greases, bitumen and solvents, as well as energy consumption in the gas production and distribution industries.
Source: Trewin, 2006; ABARE 2004, ABARE 2005

Commercial building energy use

The Federal Government owns a large number of commercial buildings and carries out regular audits of these buildings to gauge their environmental performance. The table below shows a range of building types and their average energy consumption. It is interesting to note in some cases the least efficient building uses more than ten times the energy of the most efficient. While some of this energy use will be driven by harsher operating conditions or longer operating hours, much of it will be due to the inherent inefficiency of the facility.

Energy use in Australian Government buildings

End-use	GJ	Lower	Upper	Average	Key indicator
Office — Tenant light and power	1,187,697	4,007	25,692	8,724	MJ/person/annum
Office — Tenant light and power*	1,187,697	223	1,427	485	MJ/m2/annum
Office — Central services	535,650	32	912	441	MJ/m2/annum
Public buildings	349,839	609	5,966	1,102	MJ/m2/annum
Law courts	100,602	245	794	600	MJ/m2/annum
Climate controlled stores	48,817	391	3,028	738	MJ/m2/annum
Laboratories	962,349	563	2,061	1,131	MJ/m2/annum
Other buildings	634,466	3	13,637	830	MJ/m2/annum

• Based on density of 18 people/m²
  Source: Australian Greenhouse Office, 2006b
  

Office buildings

Government audits reveal that the average energy consumption for an office building in Australia is around 1,000 MJ/m²/annum, although some office buildings can use as much as 1,900 MJ/m²/annum. This energy use is split relatively evenly between central services and tenant light and power. The top left graph shows the distribution between these two groups.

Central services energy is dominated by the energy requirements of the heating, ventilation and air-conditioning (HVAC) system, while other items, such as common-area lighting, lifts and hot water, make small contributions to the total. The majority of tenant area energy use is for lighting, although office equipment contributes a significant amount. The bottom left chart shows the average breakdown of the various energy uses within a typical office building.

Hospitals

Traditionally, hospitals are considered large energy consumers, with significant consumption of electricity and gas. However, studies of their energy consumption are limited and detailed data is not readily available. One study that was conducted reviewed the energy consumption of Victorian hospitals. This study found that the average electricity consumption was 695 MJ/m² of gross floor area, although this ranged from 50 MJ/m² to 3,586 MJ/m². Gas consumption averaged 1,574 MJ/m² (Tucker et al., 2001). This is lower than data obtained from the US, which reports an average consumption of 1,065 MJ/m² (E Source, 2006).

US data also reveals that the majority of energy in hospitals is consumed by HVAC, lighting and water heating (US Department of Energy, 1998).

Retail

The retail industry is the largest employer in Australia, employing about 920,000 people (about 12% of the workforce). Around 70,000 retail businesses transact some $150 billion worth of business each year, consequently making the retail sector the fifth highest emitter of greenhouse gases in Australia (Energysmart, 2006).

US surveys show that lighting is the dominant energy user in retail buildings, accounting for 37% of the total energy use (US Department of Energy, 1998).

Links:
Australian Bureau of Statistics
Australian Greenhouse Office
Energysmart

The importance of energy efficiency

• Why is it important?
  • Benefits for the triple bottom line
  • Benefits for owners
  • Benefits for developers and contractors
  • Benefits for designers
  • Benefits for occupiers
• What are the benefits?
• What are the risks?
  • Assessing the value
  • Assessing the risk

Energy efficiency refers to gaining the same or a higher level of useful output, using less energy input. Energy efficiency is important in both stationary and transport energy.

Technical energy efficiency is energy efficiency that comes from new and improved technologies and equipment (e.g. energy-saving appliances, co-generation and high-efficiency lights) or operational practices (e.g. energy-efficient design or just switching off lights and equipment when not in use).

Energy intensity measures the energy used to produce a certain outcome, whether it be a widget or GDP. Improved technical energy efficiency will lead to lower energy intensity, all other things being unchanged (Commonwealth of Australia, 2004).

Energy efficiency improvements in Australia have occurred more slowly than in other nations. From 1973-74 to 2000-01, technical energy efficiency in Australia improved by 3%. The International Energy Agency has found that Australia's energy efficiency has improved at less than half the rate of other countries (International Energy Agency, 2001).

Australia's poor performance can be linked to several factors. Investments in energy efficiency increase economic welfare only when they replace less productive investment or meet commercial return benchmarks. As an environmental measure, increased energy efficiency needs to represent a lower-cost solution than alternatives before becoming attractive. However, energy efficiency has consistently proved the most cost-effective of Australia's responses to greenhouse emissions.

Lower energy prices in Australia are one factor driving our poor energy efficiency performance. Lower energy prices reduce the commercial attractiveness of some energy efficiency opportunities, making them less likely (or rational) for individuals or businesses to pursue. However, our lower energy prices are not the only factor, as countries with similar energy prices (like the United States and Canada) have experienced higher growth in energy efficiency than Australia.

Why is it important?

Energy use is the dominant source of greenhouse gas emissions in Australia, contributing 68% of the nation's total emissions in 2003 (Commonwealth of Australia, 2004). As is now accepted, these emissions are a major contributor to global warming and, consequently, it has become imperative to improve energy performance across all sectors.

Energy efficiency offers the largest and most cost-effective opportunity for both industrialised and developing nations to limit the enormous financial, health and environmental costs associated with burning fossil fuels. Globally, it is estimated that tens of billions of dollars per year are invested in cost-effective energy and water efficiency solutions. However, the actual investment level is far less, representing only a fraction of the existing, financially attractive opportunities for energy-saving investments.

It has been estimated that increasing the uptake of commercial energy efficiency opportunities could increase GDP by $975 million a year and could significantly reduce greenhouse gas emissions (Commonwealth of Australia, 2004). Indeed, it has been demonstrated that energy-efficient buildings can cut their energy consumption, and consequently their energy bills, by up to 60%. This represents a major cost saving to both building owners and tenants.

Benefits for the triple bottom line

Buildings impact significantly on our environment, consuming 32% of the world's resources, including 12% of the world's fresh water and up to 40% of the world's energy. Buildings also produce 40% of waste going to landfill and 40% of air emissions (OECD, 2001). In Australia, commercial buildings produce 8.8% of national greenhouse emissions and have a major part to play in meeting Australia's international greenhouse targets (Australian State of the Environment Committee, 2001).

Studies into energy use of Australian Government buildings reveal that many commercial buildings are responsible for 200 tonnes of greenhouse gas emissions per square metre of floor space annually. The table below lists several commercial building types with their average greenhouse gas emissions.

Energy use indicators for building types

End-use	GHG (tonnes)	GHG average (tonnes)	GHG key indicator
Office — Tenant light and power	300,289	2,206	T/person/annum
Office ---T enant light and power*	300,289	123	T/m2/annum
Office — Central services	101,651	84	T/m2/annum
Public buildings	63,145	199	T/m2/annum
Law courts	22,737	136	T/m2/annum
Climate controlled stores	9,152	138	T/m2/annum
Laboratories	173,445	204	T/m2/annum
Other buildings	150,196	196	T/m2/annum

• Based on density of 18 people/m²
  Source: Australian Greenhouse Office, 2006b

Electricity use is the main source of greenhouse gas emissions in commercial buildings, being responsible for 89% of all emissions (Australian Greenhouse Office, 1999).

The dominance of electricity in the greenhouse makeup is reflected in the end-use sources of greenhouse gas emissions. HVAC-related equipment dominates, being responsible for 63% of all emissions, while lighting represents 21% of the total. Both these use areas are high electricity consumers.

Government buildings (public administration and community services) produce the most greenhouse emissions, generating approximately 12 Mt of CO₂ per annum (36% of total commercial building sector), based on a 1990 study. The retail/wholesale sub-sector is a close second, at 32% of total commercial building emissions (Australian Greenhouse Office, 1999).

Benefits for owners

Owners of commercial buildings have much to gain from investing in energy-efficient systems and ensuring efficient operation and maintenance. There are economic benefits through reduced operating costs, especially from HVAC systems. Owners are usually responsible for the costs related to central services energy. Studies show that central services energy accounts for almost half the entire energy used in a typical commercial building. The majority of this is consumed by the central HVAC system and, therefore, ensuring that these systems are efficient and controlled effectively can result in significant savings to the building owner.

Demand for green buildings is set to rise dramatically in the near term, causing a major reshaping of the commercial office rental market. Federal and state governments, two of the largest tenants of office space in Australia, are raising the environmental performance requirements of their accommodation. Many major corporate tenants are going down a similar path, either to demonstrate environmental responsibility or to capture the productivity benefits that are now being documented in green buildings. For example, the Victorian Government has a target of reducing the energy consumption by 15% in buildings owned and/or occupied by each department and statutory authority within the general government budget sector (Sustainable Energy Authority Victoria, 2001). This includes offices, schools, TAFEs, police stations, prisons, courts, research facilities, hospitals, and health and community services. Public housing and small-scale residential services are excluded from meeting this target.

The Federal Government also has a policy regarding its sourcing of building space. Energy efficiency in government operations (EEGO) is an updated version of the Australian Government's 1997 policy Measures for improving energy efficiency in Commonwealth operations. The policy has several aims, including:

'[to] provide an enhanced proactive management framework for agencies to identify, monitor and manage their energy consumption by specifying minimum energy performance standards (generally 4.5 stars on the Australian Building Greenhouse Rating (ABGR) or equivalent scheme) in contracts, leases and other relevant documentation for new buildings, major refurbishments and new leases over 2,000m²' (Australian Greenhouse Office, 2006a).

Government office portfolios are a major component of the rental market in all capital cities. Their sheer scale will create a green buying block to which the property industry will have to respond. Smaller tenants are also seeking green accommodation, but are facing a dearth of green buildings that they can lease.

Benefits for developers and contractors

Investing in energy-efficient technologies is still seen by many developers as a financially risky undertaking. A recent report, Green buildings in Australia: drivers and barriers, authored by Swinburne University of Technology's civil engineering professor, Dr John Wilson, states that the construction industry is overwhelmingly driven by financial performance and measures success through three key criteria: cost, time and quality. Consequently, the value of incorporating green technologies and design into buildings is only seen in financial terms (Svircas, 2006).

Given the direction of greenhouse policy and the Ministerial Council on Energy commitment to have all commercial buildings rated, it may not be long before developers realise the risk associated with building properties that aren't efficient. Poor energy efficiency could lead to buildings that are hard to sell or lease.

The Green building market report 2006 amalgamates information drawn from a survey of 212 Australian construction and property professionals, predicting the impact that green buildings will have on the industry and identifying trends for the next couple of years.

The report, a joint project of the Green Building Council of Australia and Building and Construction Interchange (BCI) Australia, was commissioned as the demand for green buildings grows, particularly from the government sector and from large corporate building tenants and owners.

The Green Building Council's cost-benefit analysis of green buildings, The dollars and sense of green buildings, shows that while green buildings can incur a small premium above the costs of standard construction, growing international and local evidence shows the industry should not expect the cost to build 'green' to exceed a 3% premium (Green Building Council of Australia, 2006).

Benefits for designers

A recent survey of the construction industry indicates that 84% of Australian architects, contractors and building owners are involved in green buildings (Green Building Council of Australia & Building and Construction Interchange, 2006). Consequently, for the design industry, the importance of understanding and incorporating energy-efficient principles into building designs is an essential part of their overall skill set.

Clients, particularly government clients, are driving the push for more sustainable buildings. For example, the Victorian Government now requires that each new office leased or built by the Victorian Government needs to meet Australian best practice including:

• a 4-star Green Star rating (using the rating tools Office Design and Office Interiors)
• a 4.5-star energy rating for base buildings and a 5-star rating for tenancies (under the Australian Building Greenhouse Rating Scheme).

Benefits for occupiers

Like building owners, tenants are large energy users, accounting for half the total energy costs of a typical commercial building. The majority of this is in lighting and appliance energy use.

Tenants have direct control of the types of electrical equipment they use in their work environment and how these are managed. Buying and using energy-efficient equipment saves money. It can provide enormous savings in electricity use alone, saving up to $180 per 1,000 kilowatt-hours of energy and cutting up to 80% off electricity bills. If tenants are responsible for HVAC running costs, being energy-efficient can also cut 20%-30% off this bill because of reductions in the amount of heat that equipment generates, leading to a reduction in associated cooling of that load (NAEEEC, 2001).

The environmental benefits of using energy-efficient equipment are tremendous. By reducing electricity use, air and water pollution from power stations are also reduced and one tonne of greenhouse gas is saved for each 1,000 kilowatt-hour of electricity saved.

Tenants also have discretionary powers when it comes to selecting the type of building they are interested in leasing. Assessing the building for its energy-efficient features should be part of the overall selection process. Features that tenants should pay special attention to are the systems that they usually pay for, such as lighting systems. Selecting buildings that have energy-efficient lighting systems will have a significant impact on electricity costs.

The Australian Government has established its own targets as tenants of buildings through its Energy efficiency in government operations (EEGO) policy, which requires agencies to achieve energy intensity portfolio targets by the 2011-12 financial year. These targets are:

• 7,500 MJ/person/annum for office tenant light and power
• 400 MJ/m²/annum for office central services (Australian Greenhouse Office, 2006a).

What are the benefits?

In Australia, energy users currently spend around $50 billion annually on energy. Government program experience, advice from energy auditors, and independent analysis suggest that many businesses and households can save 10% to 30% on their energy costs without reducing productivity or comfort levels. In many cases, these savings have very short paybacks under current energy prices. Achieving these reductions could deliver $5 to $15 billion in potential savings from energy, but would require significant investment in new equipment and changes to existing practices. Experience and analysis indicate that these investments would have a positive net present value over the life of the investment, and that many have paybacks in as little as six months (Commonwealth of Australia, 2004).

Recent analysis, done as part of the National Framework for Energy Efficiency (NFEE) , identified substantial areas where commercial energy efficiency opportunities are not being taken up. It found that significant energy efficiency opportunities with paybacks of four years or less exist across the commercial, residential and industrial sectors.

The analysis estimated that if half of these gains were commercially attractive, implementing them would increase GDP by around $975 million a year once fully implemented. The analysis did not encompass the transport sector (Commonwealth of Australia, 2004).

Work done by the Council of Australian Governments (COAG) identified substantial economic gains from facilitating demand-side responses in the national energy market (COAG, 2002). It estimated that improving market arrangements in this area would increase GDP by about $630 million a year. Some of the economic gains identified by COAG flow from improved energy efficiency, while the remainder come from other sources, like commercial decisions to stop (or lower) production, or to switch off appliances, in response to prices.

ABARE estimates that the commercial sector as a whole has the potential for a 10.4% improvement in energy efficiency, saving 23 petajoules of energy annually.

What are the risks?

All organisations employ basic financial analysis tools to examine the value, risk and liquidity impacts of investment opportunities competing for limited capital resources. To successfully compete against other business investments, energy-efficiency projects need to be evaluated on the same basis.

All organisations evaluate potential investments based on the financial bottom line. To evaluate this bottom line, organisations use financial analyses to identify whether an investment passes a predetermined profitability hurdle rate, while maintaining acceptable first cost and liquidity requirements. Profitability is typically measured by whether a project's internal rate of return passes the organisation's investment hurdle rate. Cash flow and liquidity are evaluated by first cost and payback.

Assessing the value

Investment in energy-efficiency projects is a long-term investment and should be analysed accordingly.  One of the current best practice techniques available for verifying results of energy-efficiency projects is the International performance measurement and verification protocol (MVP). The MVP provides an overview of current best practice techniques available for verifying results of energy efficiency, water efficiency, and renewable energy projects. It may also be used by facility operators to assess and improve facility performance (IPMVP Committee, 2002).

Valuating risk
According to Sugiyama (2001), the current valuation approach commonly used in new commercial construction projects is often too haphazard when it comes to analysing energy efficiency. There are many valuation approaches available, but most of them target an individual energy efficiency measure and are not applicable to a wide range of situations. This is due to the fact that the construction of a building involves a wide range of technologies and experts, and it becomes difficult for owners to respond to a single authoritative voice in understanding and analysing their options. The owner is often the sole entity that oversees the entire process, while architects, mechanical engineers, electrical engineers, contractors, and manufacturers all serve narrower, professional roles (Sugiyama, 2001).

Assessing the risk

Classifying the risk level of an energy-efficiency project can be difficult. Because of uncertainty about future events (e.g. the price of electricity in the year 2010), anticipated cash flows may be difficult to estimate. However, compared with other investments that a company may make, such as new product development, energy-efficiency projects are widely considered to be low risk. Where the risk levels of other investments that an organisation is considering are unknown, the risk of energy-efficiency investments is often classified as neutral, in order to be conservative (US EPA, 1998).

The prospect of a carbon trading scheme is one risk that is likely to cause definite shifts in the accounting of energy-efficiency investments.  Depending on how they operate and how the costs will pass through the entire economy, such schemes could result in what would today be regarded as a border-line or even high-risk investment suddenly becoming a low-risk investment.

Sources of major impact

• Embodied energy
  • Embodied energy of materials
  • Embodied energy of commercial buildings
  • Calculating embodied energy
• Operational energy
  • HVAC
  • Lighting
  • Appliances

Traditionally, when people think of energy consumption in buildings they are thinking of operational energy (i.e. the energy that is required to run services such as HVAC, lighting and appliances).  Indeed, operational energy is the main consumer of energy in a building over its lifetime and is one of the primary areas that can be targeted to improve energy efficiency.  However, energy is also consumed in the manufacture of materials that go into a building's structure and a building's fit-out.  This type of energy is known as 'embodied energy' and although not as significant as operational energy, can be a major source of energy consumption within a building over its lifetime.

In commercial buildings, operational energy is dominated by two main areas: HVAC and lighting. Both these systems have enormous potential for improvement in terms of energy efficiency. Office equipment is also a significant energy consumer and is a particularly important area to tenants, who are usually responsible for the costs of running this equipment.  Significant energy saving potential is available here as well. 

The main source of embodied energy use in a commercial building is the structural elements of the building (e.g. walls and floors). It has been estimated that for some commercial buildings the embodied energy can be equivalent to 20 to 37 years of operational energy and consequently, it is a major source of energy consumption within a building.

Embodied energy

The concept of embodied energy is an area of environmental assessment that has started to be included in life cycle energy calculations of buildings. Embodied energy is defined as 'the quantity of energy required by all of the activities associated with a production process, including the relative proportions consumed in all activities upstream to the acquisition of natural resources and the share of energy used in making equipment and in other supporting functions (i.e. direct energy plus indirect energy)' (Treloar, 1994).

Like operational energy, embodied energy is an indicator of the level of energy consumption for a building. Reducing energy consumption through better design has been a goal of designers for many years, but the embodied energy portion of this consumption has largely been ignored. There are several reasons for this omission, including no clear assessment methodology, lack of data, lack of understanding, and a common belief that the embodied energy portion of a building's energy consumption is insignificant. However, over recent years, the methodologies for assessment have improved, data reliability and access has increased, and reports have indicated that the embodied energy portion may be as high as 20 times the annual operational energy of an office building (Tucker et al., 1993).

Embodied energy of materials

The embodied energy per unit mass of materials used in building varies enormously from about two gigajoules per tonne for concrete to hundreds of gigajoules per tonne for aluminium. Using these values alone to determine preferred materials is inappropriate because of the differing lifetimes of materials, differing quantities required to perform the same task, and different design requirements.

Embodied energy of commercial buildings

For a commercial building, the greatest concentration of embodied energy is typically located in the structural elements of the building (walls and floors).

Calculating embodied energy

Calculating the embodied energy intensity of a building requires identification of the energy consuming processes and calculating their contribution within the total product creation process. This usually involves several individual actions.

To be able to quantify the energy embodied in the construction of a building, the quantities of materials must first be estimated, through a process of disaggregation and decomposition to a level of detail that allows for the separation of components into their principal materials. Energy intensities of each material can then be multiplied by the quantities of individual materials and the products aggregated to obtain the total for each material, element or whole building. In addition to the embodied energy value, the CO₂ emissions resulting from the energy production are also a significant indicator of the environmental impact of a building. This is particularly so in Australia, where the vast majority of our energy production is from coal. CO₂ is a significant greenhouse gas, and quantities produced are directly related to embodied energy consumption. On average, 0.098 tonnes of CO₂ are produced per gigajoule of embodied energy (Ambrose & Tucker, 1996).

Links:
CSIRO
Your Home

Operational energy

Operational energy is the main consumer of energy in a building over its lifetime and is the primary area that can be targeted to improve energy efficiency. In commercial buildings, operational energy is dominated by two areas: HVAC and lighting. Both these systems have enormous potential for improvement in terms of energy efficiency. Office equipment is also a significant energy consumer and is a particularly important area to tenants, who are usually responsible for the costs of running this equipment. Significant energy saving potential is available here as well.

HVAC

Heating, ventilation and air-conditioning systems (HVAC) are designed to maintain and control air temperature, humidity and quality. HVAC systems are needed in most buildings to provide comfort for the occupants and to ensure equipment works properly. They are one of the biggest consumers of energy within a building, accounting for 36%-60% of the total energy use in commercial buildings. It is estimated that by 2010, HVAC energy use will be responsible for 21 Mt of CO₂ emissions annually, or nearly 4% of Australia's total emissions (Energy Strategies, 2005).

There are many different types of air-conditioning systems, but they can be grouped into the following categories:

• Centralised ducted air systems: These are systems in which the primary movement of thermal energy (i.e. heating and cooling) around the building is via conditioned air. These systems are the most common in large office buildings.
• Centralised chiller plant systems: These are systems in which a fluid — typically water, but possibly refrigerant — is used to move heat around the building. These systems are fairly common in office buildings.
• Decentralised systems: These are systems in which conditioning of the air occurs locally, with little or no bulk movement of thermal energy around the building. These systems are relatively common in small offices.

Link:
Energy rating: Climate control — heating, ventilation, air-conditioning and efficiency

Lighting

The amount of light radiated by a lamp is measured in lumens. The lamp's 'efficacy' is given as the ratio of lumens per watt of electric input. Generally speaking, higher-efficacy lamps are more energy-efficient, but lamps with the greatest efficacies also tend to have the highest wattages. Therefore, purchasers and specifiers should choose the most efficacious lamp that is appropriate (in terms of light output, colour and other factors) for a given application (American Council for an Energy-Efficient Economy, 2006).

The most commonly used light sources in commercial applications include:

• incandescent lamps
• fluorescent lamps
• high-intensity discharge (HID) lamps
• light emitting diodes (LED) lamps.

Fluorescent lamps are the most common lamp type in commercial buildings and are by far the largest source of lighting energy use in commercial buildings.

Appliances

Appliances contribute a significant amount to the overall energy use of a typical commercial building. Office buildings have particularly high energy consumption from the range of office equipment that is used.

Most general office equipment is now part of the Energy Star program and consequently provides users with the option of utilising the built-in energy-efficient measures. Nevertheless, users need to activate these functions in order for the full efficiency benefits to be realised.
Computers and monitors
Desktop computers generally draw about 40-50 watts when in use. Standard cathode ray tube (CRT) monitors usually use 50-100 watts, with lower values becoming more common. This is lower than the values that are usually shown on product nameplates and data sheets because the maximum likely consumption is usually given and not the average.

The power needed to light up a screen varies according to the area of the screen. That means that moving from a 15-inch to a 17-inch screen at constant efficiency will generally increase power demand by about 30%. However, because inefficiencies vary markedly between models, some 17-inch screens use less energy than some 15-inch screens. An audit of more than 600 computers and monitors at the University of New South Wales revealed that:

• the average computer uses 49 watts when fully on, 29 watts when asleep, and 2 watts when switched off (these numbers reduce to 0 if the equipment is switched off at the power-point, rather than just at the 'off' button on the equipment)
• the average monitor uses 60 watts when fully on, 6.5 watts in deep sleep, and 1 watt when switched off.

Today, LCD monitors or flat-panel displays are quickly replacing traditional CRT computer monitors. LCDs use less space than traditional monitors and, importantly, also use less energy. In some cases, the energy consumption of an average LCD display can be half to two-thirds of that for an average CRT.

Laptop computers, including their flat liquid crystal display (LCD) screens, are even more energy-efficient, typically using 15-25 watts when fully on. By selecting an efficient laptop computer and operating it efficiently, energy use can be reduced by 98-99%. Likewise, replacing a standard CRT monitor with an LCD monitor also saves energy, as well as desktop space (NAEEEC, 2001).

To meet Energy Star requirements, computers with a power rating of 200 watts or less must have a sleep mode of no more than 15 watts. Monitors must have a sleep mode of 15 watts or less, and a deep sleep mode of 8 watts or less.

While a significant proportion of Energy Star models only just meet these standards, others beat them by a wide margin. For each of these three sleep modes, the US EPA product database lists models powering down to almost zero watts. The wide variation confirms the importance of buying best practice products in preference to those that just meet Energy Star requirements.

Photocopiers

The major part of photocopier energy use is the heating of the components that fuse toner to paper. These components are often kept hot when the machine is idle, so power consumption can stay high unless the machine is switched off or power-managed.

Photocopier energy use is affected by the following factors (NAEEEC, 2001):

• Warm-up time: If the machine warms up quickly, it can be switched off when not being used. The best office copiers warm up in less than ten seconds, while small home office machines warm up even more quickly.
• Consumption while copying: Electricity consumption while copying varies from a few hundred watts to several kilowatts, generating from a quarter to more than three kilograms of greenhouse gas emissions and costing from four to 45 cents per hour of continuous copying. Each time photocopying starts, the machine uses extra energy to get ready to operate. Energy can be saved by 'batch copying,' which involves saving up copying tasks and doing them in one batch.
• Stand-by consumption when switched on but not copying: Keeping the operating components of the photocopier warm or on stand-by, ready for immediate copying, uses from 15 to 400 watts of electricity. This generates a kilogram of greenhouse gas emissions every 2.5 to 65 hours and costs from 0.2 to 6 cents per hour. It is far better to power-manage the machine.
• Power management features: Some older models of photocopiers have 'energy save' buttons that are supposed to reduce energy consumption while the machine is on stand-by, but which in reality save little or no energy. However, the newer Energy Star photocopiers include an efficient energy save button in their range of power management features.
• Energy consumption when switched off: Some copiers have small electric elements of up to 50 watts that operate continuously unless the photocopier is switched off at the power-point. These are only needed in humid environments.
• Energy consumption of accessories: Document feeders and collators may consume a lot of energy if they don't power down with the rest of the machine.

Printers

Laser printers use similar technology to photocopiers, so their energy consumption is similar to that of small photocopiers. Inkjet or modern dot matrix printers can provide very high print quality, but they are slower than laser printers.

The Energy Star program has resulted in much more efficient laser printers being developed. These can rival the better inkjet printers in sleep mode, but they still use more energy while printing.
Fax machines

Before the introduction of the Energy Star program, very few fax machines had a sleep mode. However, now most of them do. Since November 2000, Energy Star requirements for fax machines have been the same as for printers.

Over the past few years, fax and printing technologies have moved much closer together, to the point where there are now many combined fax/printers on the market. Therefore, many of the guidelines for buying environmentally friendly printers apply to fax machines too. Because most fax machines send and receive faxes for only a small proportion of their operating time, the energy they use in stand-by and sleep modes is important. There are models available that consume from 0.5 to two watts in sleep mode, while others just meet Energy Star requirements.
Links:
Green office guide
Energyrating
Energy Star

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