There are numerous initiatives which can help improve the energy efficiency of heating, ventilation and air conditioning (HVAC) systems. An effective HVAC strategy relies on an integrated approach which combine the strategies outlined below.

For information on types and components of HVAC systems, see Technology background – Heating, Ventilation and Air Conditioning.

Reduce demand for HVAC services

Various methods exist to reduce mechanical heating and cooling demand including improved building insulation, high-performance window glazing, natural ventilation, external window shading and proper window coverings. Painting roofs white can, in ideal cases, reduce air-conditioning loads by as much as 20%.12 Controlling internal heat generation from lighting and equipment, and minimising air leakage, can also reduce cooling and heating loads.

Some examples of opportunities in this area are outlined below.

Implement holistic HVAC demand management

A number of factors influence the heating and cooling load on a HVAC system. Reducing the demand from any of these factors will reduce the size of the HVAC system required and the energy used and costs involved.

There are three main factors that affect the demand on a HVAC system to achieve energy savings:

  1. The design, layout and operation of the building affect how the external environment impacts on internal temperatures.
  2. The heat generated internally by lighting, equipment and people, or removed by refrigeration equipment or fans, all have an impact on how warm or cool your building is.
  3. The amount of temperature difference between a conditioned space and its environment (temperature set points).

For more information

Optimise building design, layout and operation

Factors such as the building’s orientation, thermal mass, daylighting, and insulation combine to affect how the external environment impacts on internal temperatures and the energy consumption of the building. It is possible to reduce energy requirements for HVAC systems through the following steps:

  • Where appropriate, use passive solar design techniques to heat and cool areas, such as allowing direct sunlight to penetrate windows in winter and using shading and natural ventilation in summer. Be aware that buildings that are well insulated, and/or generate a lot of internal heat, may not need more solar gain, even in winter. Also, sun glare and radiation can impact on amenity, comfort and productivity.
  • Well-sealed high-performance glazing, external window shading and proper window coverings can yield significant energy savings. The use of double-glazing and/or low-emissivity windows can dramatically reduce heat loss during winter and minimise the amount of heat entering during the summer.
  • Improve the air-tightness of a building by sealing areas of potential air leakage. Exhaust fans and make-up air suppliers can act as air leaks when they are not in use. Installing dampers can minimise these leaks. Where multiple stories of a building are interlinked, powerful chimney effects can accelerate air loss. Openings on more than one side of a building can also increase the air leakage linked to wind effects.
  • Use high levels of insulation, optimise glazing areas and reduce the infiltration of outside air to minimise heating requirements. However, if internal heat generation is high (via body heat and electrical equipment), insulation can increase annual HVAC use by increasing the need for cooling. This can be managed with economy cycles and natural ventilation. A thermally leaky building envelope is a liability in extreme weather, so it is generally preferable to minimise heat flows and to use ventilation systems to manage internal heat loads and indoor environmental quality.
  • Cooling requirements can be minimised through economy cycles, openable windows and user-controlled local environments (e.g. small fans or local controls) which enable a larger comfort range and a reduction in air-conditioning loads. An economy cycle has a large fresh air intake and a large spill or relief air outlet. Rather than recirculating most of the air in the building, as is normally done, the air is not recirculated. It simply comes in, provides cooling, then is vented out again. An economy cycle automatically increases the portion of outside air used in the air conditioning when cooling is required and the outside air is cooler than the return air.
  • Minimise the space being heated or cooled by closing doors to unused or unconditioned rooms.

Assess cool roof application

Cool roofs reduce heat transfer into buildings by reflecting solar radiation. Less heat transfer means less demand for air conditioning. Cool roofs can have a payback period of a few years, depending on the air-conditioning configuration and building use. In a US example, applying a 60% reflective paint to the roof of an existing low-rise medical office building cost about US$2.20/m2 and reduced energy consumption by 18%; incorporating an 85% reflective coating to the roof of a new mixed-use building reduced electricity consumption by 18%.1

Until recently, white or light-coloured paints, coatings and tiles were the only roofing surfaces that could achieve high albedo (solar reflectivity). Today, high-albedo coatings and tiles come in a variety of colours although white still gives the best results.

Cool roof efficacy depends on a number of factors:

  • local climate (temperatures and the amount of incident sunlight)
  • the proportion of the year when heating and cooling are needed; white roofs can be a negative in winter or in colder climates
  • the proportion of roof area to building volume; white roofs are most effective on single storey buildings
  • roof insulation, sarking and ventilation which all reduce the amount of solar thermal radiation that passes through the ceiling of the building
  • local building regulations/planning laws etc (white roofs may not be allowed in some zones)
  • roofing materials, which affect the costs of recoating and its durability
  • roof angles, which affect how much of the roof is shaded at certain times of day, and the angle at which direct sunlight strikes the surface.

Green roofs

Rooftop gardens also help to keep roofs cool by absorbing and using solar radiation. University of Melbourne research shows a 48% decrease in cooling load for spaces under a green roof, while winter heating loads were also reduced by 13%.2 The garden roofs can also provide a more comfortable microclimate.

Some issues to be considered when planning a green roof are maintenance costs, irrigation needs, personal safety, structural pressure and pest infestation.

Footnotes ~ Show 2 footnotes

  1. Pacific Gas Electric Company (undated) Cool Roof: Design Brief. Pacific Gas Electric Company (Opens in new window) PDF 532 KB
  2. Ker, P. (2011) Roof gardens to have their day in the sun. The Age

Reduce heat generation from lighting and equipment

In order to keep the internal environment comfortable, much of the heat produced by electrical lighting, appliances and office equipment must be mitigated by air conditioning or ventilation. The amount of heat released can be reduced by bringing daylight into the building, turning off unused equipment, and upgrading items such as lamps, computers, printers, photocopiers and motors to more efficient models.

Using LED lighting can achieve additional energy savings by further reducing the heating load compared to that achieved by CFLs.

For more information

Optimise temperature and humidity 'set points' to save energy

Optimising temperature and humidity set-points saves energy. The set points are chosen at a temperature and humidity level determined by the building’s occupants to ensure their air conditioned space is comfortable. A higher set point in summer and a lower one in winter leads to reductions in HVAC energy use. When the temperature or humidity level rises above the set point in summer or drops below it in winter, the HVAC’s control measures work to return the ambient temperature to the set point.

Optimise the use of existing HVAC systems

HVAC system optimisation may require the use of control systems and thermostats, modifications to the ventilation and distribution systems, and the relocation of the HVAC unit.1

Investing in improved control and zoning, and good maintenance can result in substantial energy savings. Advances in control engineering now enable the measurement of many factors that influence the comfort of building occupants.2 Optimising these factors, including ventilation and air distribution systems, can yield further energy savings.

Some examples of opportunities in this area are outlined below.

Footnotes ~ Show 2 footnotes

  1. Smith, M., Hargroves, K., Stasinopoulos, P., et al (2007) Energy Transformed: Sustainable Energy Solutions for Climate Change Mitigation (Lecture 2.3) Commonwealth Scientific and Industrial Research Organisation, Griffith University, The Australian National University, The Natural Edge Project
  2. Hordeski, M.F. (2001) HVAC Control in the New Millennium. Fairmont (Opens in new window) PDF 4.2 MB

Utilise control systems

Control systems that are adequately commissioned and programmed will reduce HVAC energy consumption by ensuring that the right amount of air conditioning is provided when and where it is required.

The most effective control systems can completely shut down part of the distribution circuit, be adjusted to prevent simultaneous operation of heating and cooling systems, and have default settings that are suitable for the building. For example, time-switches are a low-cost technology for switching on and off HVAC systems at specific times, such as an hour before a shift starts and an hour before a shift ends.

Implemented well, this has a negligible effect on the occupants’ comfort because the building’s thermal mass maintains a similar air temperature for short periods of time. Public holidays can also be programmed in, reducing annual running time. ‘Intelligent’ time-switches ascertain the optimal operating period, potentially reducing operating time even further.

Utilise temperature controller thermostats to reduce demand and save energy

Temperature controllers can be programmed to maintain fan operation while cycling HVAC unit operation. Two-stage temperature controllers reduce energy consumption by activating various components of the HVAC system (e.g. HVAC unit, economiser, two-speed motor, heat pump, a second HVAC unit) as the demand for its services arise.

Poorly located temperature sensors can increase energy consumption substantially. They provide inaccurate readings when located in direct sunlight, near hot equipment, in drafts or when isolated behind doors or curtains. Multiple thermostats with conflicting temperature set-points make HVAC systems work against each other, increasing energy consumption.

Optimise and streamline air distribution systems

Energy savings in the distribution system are often very cost effective because they reduce the demand for fan power and HVAC unit capacity. Optimising the distribution system reduces running costs and improves indoor comfort. Poor distribution system design can reduce supply flow-rate, which can contribute to coil icing and can reduce air conditioning efficiency by about 10%.1

There are several considerations in selecting and integrating distribution system components:2

  • An increase in the air duct’s cross-sectional area by 15% will increase the duct cost by around 15%; however, this will reduce the friction rate by 50%, reduce pressure drop contributed by ducts by 50%, reduce overall pressure drop in the distribution system to the order of 40% (when diffuser losses are included) and reduce fan energy consumption in the order of 15–20%.
  • Appropriate air duct layout and the use of efficient fittingshelp to minimise pressure loss and cost. Consider that:
    • straight ducts have lower pressure losses and lower cost than duct turns
    • sound spiral ducts have lower pressure loss, cost less and are easier to install than ducts with longitudinal joints
    • smooth wye (Y-shaped) branch fittings have lower entrance pressure losses than right angle fittings
    • turns that are immediately before a supply or return-air register increase pressure loss and decrease diffuser performance.
    • Sealing ducts to prevent air leaks saves energy by reducing ventilation capacity, reducing HVAC unit capacity and preventing undesirable heat transfer.3
  • Insulating ducts also prevents undesirable heat transfer. Installing insulation to at least 50 mm, R1.5 is cost-effective for ducts outside of the air-conditioned space and is required for HVAC systems under the Building Code of Australia (Section J). Duct wrap insulation is preferable to lined duct, which increases friction losses.

Footnotes ~ Show 3 footnotes

  1. Architectural Energy Corporation (undated) Design Brief: Integrated Design for Small Commercial HVAC. Energy Design Resources
  2. Jacobs, P. (2003) Small HVAC System Design Guide: Design Guidelines. California Energy Commission
  3. Architectural Energy Corporation (undated) Design Brief: Integrated Design for Small Commercial HVAC. Energy Design Resources

Optimise ventilation systems to save energy

It is possible to save energy in the ventilation system by using the best equipment and optimising the use of that equipment:

  • High-efficiency fans and motors with direct drives (rather than belt drives) save significant amounts of energy.
  • Variable speed drives enable fan speed to match the required air flow; note that variable speed drives need good commissioning and periodic maintenance as they have a higher failure rate.
  • Demand-controlled ventilation adjusts outdoor air intake to maintain optimal indoor air quality.1
  • Preventing over-ventilation minimises undesirable heat transfer and humidity.
  • Isolating fan motors and other hot components from the supply air stream also prevents undesirable heat transfer.2

Footnotes ~ Show 2 footnotes

  1. Jacobs, P. (2003) Small HVAC System Design Guide: Design Guidelines, California Energy Commission (Opens in a new window) PDF 1.6 MB
  2. Sustainability Victoria (2006) HVAC Tips (Heating, Ventilation and Air Conditioning), Sustainability Victoria

Implement a good maintenance program

Thorough maintenance procedures assist in maintaining HVAC system energy efficiency, maintaining occupant comfort, maximising equipment life and minimising component failures. Proper maintenance can conserve space conditioning energy use through such measures as:

  • cleaning of distribution systems (fans, filters and air ducts) quarterly
  • maintaining and regularly tuning all HVAC equipment and sensors.

Use more efficient technologies

According to the Intergovernmental Panel on Climate Change 1 modern technologies can enable reductions in mechanical HVAC demand of at least 50%. As a result of this lower demand, buildings can use smaller HVAC systems and consume less energy and water (since HVAC systems often consume up to 30% of all water used in commercial buildings).2

Three of the most efficient technologies are:

Radiant chilled beams

Radiant chilled beam systems345 cool interior building spaces through ceiling pipes. The pipes carry chilled water that directly cools the space via natural convection and heat transfer. Radiant chilled ceilings are best suited to indoor spaces in large commercial buildings with low constant latent cooling loads (reducing latent cooling loads requires removing moisture from the air).

The primary challenge with these systems is that the pipes and cooling coils may accumulate condensation, potentially damaging ceiling materials and fostering biological growth. Typically, this challenge is met by managing the moisture of the indoor air by dehumidifying it before it enters the space.

Compared to a conventional variable air volume system, radiant chilled beams use less energy, are simpler to control and operate, and take up less of the building’s volume for energy distribution. Radiant chilled beams can reduce cooling energy by at least 15–20% through:

  • a targeted delivery of cooling to only those areas that require it
  • cooling with water rather than air; water requires 1/4000th the volume of air to deliver the same cooling effect (the volumetric heat capacity of water is about 4000 times greater than that of air)
  • using radiant cooling, so partially decoupling thermal comfort from air temperature and thereby losing less cooling when exhausting stale air from the building.

Displacement ventilation

Displacement ventilation (DV)6 is the supply of a ground-level flow of conditioned air into an interior space to push out stale air at ceiling level. In cooling applications, incoming chilled air forces up warm air which is expelled at the ceiling. In heating applications, DV operates like conventional mixing ventilation—warm air is supplied near the ground level, then mixes with the present air as it rises and the mixed air is expelled at the ceiling.

In either application, the supply point should be located and oriented so as to avoid air flow directly to the extraction point or into drafts. DV is best suited to spaces with a ceiling height greater than three metres and a high airflow requirement, which is usually due to high occupancy or a high contamination rate. Often the supply air is provided via a cavity under a raised floor (under floor air distribution).

Compared with conventional mixing ventilation, DV saves energy in three ways. First, it controls the climate of only the occupied zone, rather than the whole space from floor to ceiling. Less space to control means that a smaller volume of conditioned air is required. Second, the incoming air is delivered close to the occupants so the supplied air temperature can be closer to ambient temperature. Overall, ventilation efficiency is typically 0.5–0.8 for DV, as compared to 0.3–0.45 for mixing ventilation.7 Greater ventilation efficiency also means better indoor air quality, which may improve hygiene, staff wellbeing and performance. Thirdly, the lower airflow rate can, with appropriate fan control, reduce fan energy.

Climate/humidity control

HVAC systems are becoming increasingly intelligent.8 Modern computerised control systems track occupant levels, season, time-of-day, outdoor temperature and humidity levels. For example, setback thermostats adjust thermostat levels to the building’s occupancy schedule, saving 10–20% of HVAC running costs without sacrificing comfort.9

Footnotes ~ Show 9 footnotes

  1. Intergovernmental Panel on Climate Change (2007) Residential and Commercial Buildings. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press (Opens in a new window) PDF 1.1 MB
  2. Department of the Environment and Heritage (DEH) (2006) Water Efficiency Guide: Office and Public Buildings, DEH Australia
  3. Dieckmann, J., Roth, K.W. and Brodrick, J. (2004) Emerging Technologies: Radiant Ceiling Cooling. ASHRAE Journal, June, pp. 42-43 (Opens in a new window) 200 KB
  4. Roth, K.W., Dieckmann, J., Zogg, R. and Brodrick, J. (2007) Emerging Technologies: Chilled Beam Cooling. ASHRAE Journal, September, pp. 84-86 (Opens in a new window) PDF 264 KB
  5. Sachs, H., Lin, W. and Lowenberger, A. (2009) Emerging Energy-Saving HVAC Technologies and Practices for the Buildings Sector, American Council for an Energy-Efficient Economy
  6. Sachs, H., Lin, W. and Lowenberger, A. (2009) Emerging Energy-Saving HVAC Technologies and Practices for the Buildings Sector, American Council for an Energy-Efficient Economy
  7. Architectural Energy Corporation (2005) Design Brief: Displacement Ventilation, p. 5. Energy Design Resources (Opens in a new window) PDF 432 KB
  8. Hordeski, M.F. (2001) HVAC Control in the New Millennium. Fairmont (Opens in a new window) PDF 4.2 MB
  9. Sustainability Victoria (2006) HVAC Tips (Heating, Ventilation and Air Conditioning), Sustainability Victoria

Select the right HVAC unit

Oversized HVAC units are expensive, inefficient and can be less reliable.1 Capital costs are further increased due to oversized distribution ducts and components. The main inefficiency arises when the unit, running at part load, frequently cycles on and off. At every ‘on’ cycle, there is a fixed start-up period during which the unit is consuming maximum energy but providing sub-maximal heating or cooling. Frequent cycling also reduces reliability and humidity control.

A HVAC unit should meet but not exceed the calculated sensible load, latent load and supply airflow-rate, all of which depend on the size and design of the building, the heating and cooling requirements and the outdoor climate. To determine the appropriate HVAC unit size2 avoid over-estimating loads and consider:

  • effects of energy efficient technologies installed and strategies implemented, such as radiant chilled ceilings, displacement ventilation, advanced controls and any building-level energy efficiency measures
  • actual rather than rated ‘plug loads’ (the energy used by a product that is powered by an AC plug) for computers, copiers, printers and other indoor heat sources such as lighting. These items usually run at a fraction of their nameplate (maximum) loads and usually not at the same time. The plug load, which can be measured using a plug-in power meter, could be about 20% of the maximum plug device power supply rating in some cases
  • ventilation air required for the expected occupancy. Some indoor spaces have occupancy substantially lower than maximal or that suggested in building codes, which makes their cooling and ventilation loads lower than expected.

General guidelines for selecting a HVAC unit3 are as follows:

  • The unit capacity should match the calculated sensible and latent HVAC loads. Efficient units usually have lower latent capacity than standard units, and efficient buildings usually have lower sensible loads than standard buildings.
  • A unit’s supply airflow rate is proportional to its sensible air conditioning capacity. The nominal supply flow-rate of most units is suitable in moderate to very humid climates. Units with higher flow rates and sensible cooling capacities are preferable in drier climates where latent loads are lower; these units can also be smaller.
  • High-efficiency units are usually more cost-effective in the long term, but standard units may be cost competitive in some cases (e.g. a standard unit optimised for efficient part-load operating in variable environmental conditions, such as in a temperate climate).

Water-based cooling towers are a good option in drier climates as  they reduce the effective ambient temperature close to the wet bulb temperature.4  However, they use large amounts of water, chemicals, pumping and fan energy, while also having potential health risks. Evaporative pre-coolers and more sophisticated systems that use evaporatively cooled exhaust air from the building achieve a similar level of energy efficiency to cooling towers without the water consumption and health risks.

Footnotes ~ Show 4 footnotes

  1. Jacobs, P. (2003) Small HVAC System Design Guide: Design Guidelines. California Energy Commission (Opens in a new window) PDF 1.6 MB
  2. Architectural Energy Corporation (undated) Design Brief: Integrated Design for Small Commercial HVAC. Energy Design Resources (Opens in a new window) PDF 1.0 MB
  3. Jacobs, P. (2003) Small HVAC System Design Guide: Design Guidelines. California Energy Commission (Opens in a new window) PDF 1.6 MB
  4. Wet-bulb temperature is measured using a standard mercury-in-glass thermometer, with the thermometer bulb wrapped in wet muslin. The evaporation of water from the thermometer has a cooling effect, so the temperature indicated by the wet bulb thermometer is less than the temperature indicated by a dry-bulb (normal, unmodified) thermometer. The rate of evaporation from the wet-bulb thermometer depends on the humidity of the air; evaporation is slower when the air is already full of water vapour. For this reason, the difference in the temperatures indicated by the two thermometers gives a measure of atmospheric humidity. (Bureau of Meterology)

Select the right water chiller system

When selecting a water chiller system in a new installation, or if evaluating refurbishment or replacement of an existing system, calculate the cost of energy over the new system’s planned life (e.g. 25 years).

Since July 2009, the efficiency of water chillers (over 350 kWr capacity) has been regulated in Australia and New Zealand. The minimum coefficient of performance (COP)1 and the integrated part load value2 are stipulated. Chillers installed before July 2009 were not subject to these minimum energy performance standards (MEPS) regulations, and so are likely to be less efficient. Unit replacement should offer a level of energy efficiency which cannot be matched by refurbishing an old chiller.

For more information

Footnotes ~ Show 2 footnotes

  1. Coefficient of performance (COP) is the ratio of the (heat) energy moved by a heat-pump or chiller, to the energy consumed in operating the heat-pump or chiller. The higher the COP, the lower the energy consumption for a given heating or cooling duty.
  2. The integrated part load value is a time weighted value of the coefficient of performance, intended to give a more realistic indication of the in‑service efficacy of a chiller, reflecting the fact that most chillers spend only a small portion of their running time operating at full load, and the COP varies with load.

Investigate ground-source thermal options

Ground-source heat pumps (also called geothermal heat pumps) use the earth as a source for heating or as a heat sink for cooling. They therefore reduce the temperature differential across which the HVAC system must operate. Thermal piles (metal screw-rods) incorporate the ground-source heat exchanger into a building’s foundation piles, avoiding the cost of additional drilling or trenching. It is also possible to use water as heat sources/sinks for HVAC.

Select the right water heater

Many HVAC systems incorporate a hot water system to distribute heating within a building. The main appliance in this system is the water heater (often referred to as a boiler1).

The most common water heater is an ‘atmospheric’ gas-fired heater with an efficiency of no more than 80%, even at full load and significantly less at part load. When selecting a water heater in a new installation, or when evaluating refurbishment or replacement of an existing unit, calculate the cost of energy during the heater’s planned life (e.g. 25 years).

Whilst water heaters with higher efficiency tend to cost more upfront to purchase, the outlay is normally paid back in lower gas consumption costs with a reasonable return on investment. High-efficiency water heaters are usually available with modulating burner control. This improves efficiency at part load (compared with burner on-off control), by allowing more time for heat transfer against a lower temperature difference and by having fewer air-purging cycles.

Premium HVAC units are as much as 30% more efficient than standard models and are available in most sizes.2  The premium systems differ from standard units in several ways; typically, they incorporate larger condenser and evaporator coils, efficient compressors, enhanced insulation and thermostatic expansion valves.3

Some more recent technological developments include:4

  • Modulating HVAC compressors – Conventional air conditioners run at only one speed. Since even correctly-sized units mostly run at part load, they frequently cycle on and off. Modulating (inverter drive) compressors vary their output to better match the load preventing frequent cycling while increasing part-load efficiency. They can reduce energy consumption by about 20% and help to deliver better humidity control due to regular air flow, especially when variable speed air handlers are also used.
  • Dehumidification enhancement – The Cromer cycle is a combination of a desiccant wheel and a vapour compression air conditioner. In humid climates, Cromer cycle HVAC units can better match cooling loads, especially part loads, and reduce the need for reheating. They can reduce energy consumption by up to 30% and allow smaller capacity cooling equipment to be used.
  • Energy recovery ventilation – Substantial amounts of energy are required to treat very hot, humid or cold outdoor air. Energy recovery ventilation systems, most commonly heat and energy recovery wheels, exchange heat between the exhaust air and the supply outdoor air. They can lower energy consumption by about 10% and reduce the required unit capacity. Although this energy saving is modest compared to other technologies, energy recovery ventilation reduces peak loads. Some systems now evaporatively cool the exhaust air from the building and use this cooled air in the heat exchanger.
  • Economy cooling – Air conditioners mix outdoor air with recirculated indoor air. Economy cooling uses more outdoor air when cooling is required and the outside air is cooler than the return air. The systems can reduce energy consumption by about 16%. This system can be used at night to blow cool air through a building to charge the thermal mass in a process called mechanical night purge.

Footnotes ~ Show 4 footnotes

  1. In most HVAC systems with a water heater, the water does not actually boil but is heated to no more than 85°C.
  2. Jacobs, P. (2003) Small HVAC System Design Guide: Design Guidelines, California Energy Commission (Opens in a new window) PDF 1.6 MB
  3. Architectural Energy Corporation (undated) Design Brief: Integrated Design for Small Commercial HVAC. Energy Design Resources (Opens in a new window) PDF 1.0 MB
  4. Sachs, H., Lin, W. and Lowenberger, A. (2009) Emerging Energy-Saving HVAC Technologies and Practices for the Buildings Sector. American Council for an Energy-Efficient Economy (Note, this publication is free to access, but users must register first.)

Consider the HVAC unit location

The location of an HVAC unit affects its energy efficiency. When installing an HVAC device, consider the following:

  • place unit so as to minimise duct lengths
  • allow sufficient airflow around the unit
  • do not install close to heat-generating devices
  • provide easy service access without undue obstruction
  • prevent outlet air from feeding to the inlet
  • minimise acoustic and vibration disturbance in occupied spaces.1

Footnotes ~ Show 1 footnote

  1. Jacobs, P. (2003) Small HVAC System Design Guide: Design Guidelines. California Energy Commission (Opens in a new window) PDF 1.6 MB

Future developments

Developments in HVAC systems are occurring at many levels. Multiple component innovations are being packaged into advanced rooftop air conditioners to deliver energy savings of about 17%.1 Thermal energy storage technologies store heat or cold for use during later applications, helping to avoiding part-load operation and shift peak loads to off-peak times. Active solar thermal systems, a new type of heating and cooling system, use free solar radiation—available in Australia for a large portion of the year—to reduce peak demand.2 Computer technologies are increasingly improving HVAC system management and performance, and building integration.3

Some of these innovations are outlined below.

Advanced rooftop packaged air conditioners

Rooftop packaged air conditioners1 are in common use. Many have good efficiency at full load, but poor efficiency at part load where they most often operate. Increasingly, rooftop packaged air conditioners incorporate advanced features that improve part load efficiency, improve reliability and reduce energy consumption by about 17%.

Advanced features include:

  • better variable speed fans, with greater control
  • inverter controls to vary output
  • economisers, such as ventilation lockout during start-up
  • demand controlled ventilation
  • evaporative pre-cooling of the condenser unit
  • superior monitoring and diagnostics using advanced sensors.

Active solar thermal

Active solar thermal systems5 store solar radiation by heating a fluid in a collector. In space heating and cooling applications, the heat is transferred indirectly via a heat exchanger. In other applications, the hot fluid may be used directly. Active solar thermal systems do not require any energy infrastructure, and generate low or no carbon emissions. Since periods of incident solar radiation and cooling loads coincide, solar cooling reduces peak demand.

Computerised control

Computer technologies6 will continue to enhance HVAC system efficiency, reliability and intelligent control, as well as assisting with integration into other building services. Accurate and reliable measurements enable efficient HVAC operation. Intelligent controls enable post-failure diagnostics and can pinpoint predictive diagnostics and maintenance advice regarding sensor and calibration errors, fouling of sensors, faulty or poor wiring, and misaligned actuators and valves. Many advances in commercial building automation and HVAC control will come from clean room controls. Air cleanliness will become increasingly important, with more emphasis on controlling dust, bacteria, odours and toxic gases.

UV treatment

Emerging research is indicating that UV treatment of return air can deliver a high standard of air quality while reducing the dependence on outdoor air supply. This technology also reduces fouling of fans and heat exchangers, improving their efficiency. News Limited in Australia has used this technology and reduced fouling, improving efficiency more than enough to offset the UV lamp running costs.

Innovations in refrigerants

There is a great deal of innovation in refrigerants. CFCs and HCFCs are being phased out and new low emission impact refrigerants are being developed. Natural refrigerants are also being more widely used. Different refrigerants can affect energy efficiency and performance in extreme conditions.

Footnotes ~ Show 6 footnotes

  1. Sachs, H., Lin, W. and Lowenberger, A. (2009) Emerging Energy-Saving HVAC Technologies and Practices for the Buildings Sector. American Council for an Energy-Efficient Economy. Note, this publication is free to access, but users must register first.
  2. International Energy Agency (2011) Technology Roadmap – Energy-efficient Buildings: Heating and Cooling Equipment IEA
  3. Hordeski, M.F. (2001) HVAC Control in the New Millennium. Fairmont
  4. Sachs, H., Lin, W. and Lowenberger, A. (2009) Emerging Energy-Saving HVAC Technologies and Practices for the Buildings Sector. American Council for an Energy-Efficient Economy. Note, this publication is free to access, but users must register first.
  5. International Energy Agency (2011) Technology Roadmap – Energy-efficient Buildings: Heating and Cooling Equipment. IEA
  6. Hordeski, M.F. (2001) HVAC Control in the New Millennium. Fairmont (Opens in a new window) PDF 4.2 MB