Heating ventilation and air conditioning (HVAC) systems account for up to 50% of a commercial building’s energy use and dominate peak electricity demand. Capital and maintenance costs for these systems also comprise a high portion of overall building costs.
Improving HVAC efficiency can therefore have a big impact on your bottom line by reducing energy use, maintenance costs and peak demand charges. It also brings reputational benefits through higher energy efficiency ratings, such as the National Australian Built Environment Ratings System (NABERS).
A holistic HVAC strategy relies on an integrated approach to:
- reduce demand
- optimise existing systems
- upgrade to more efficient systems.
Methods to reduce demand for HVAC services include:
- improved building insulation
- high performance window glazing
- natural ventilation
- external window shading
- colour and reflectivity of external materials
- green roofs
- cool roofs.
Painting roofs white or with special reflective coatings to create ‘cool roofs’ can significantly reduce air-conditioning loads. This is especially so in hotter inland climates and for large, flat buildings like factories and warehouses.
The Global Cool Cities Alliance has developed the Cool Roofs and Cool Pavements Toolkit that includes a cool roof primer and implementation guide and searchable knowledge base.
For an overview of demand reduction options, see the Low Carbon Living CRC’s Guide to Low Carbon Commercial Buildings - Retrofit.
For estimates of upfront costs and payback periods for HVAC investments in commercial buildings, see the Clean Energy Finance Corporation’s Energy in Buildings: 50 Best Practice Initiatives.
While significant energy and capital savings can be made through investing in new, high-efficiency HVAC systems, existing systems can also be optimised.
Many factors that influence the comfort of building occupants can be measured and optimised. Such factors include humidity, air movement and surface temperatures of nearby objects, like windows.
Consider practices like:
- altering control algorithms and schedule
- adjusting thermostat set points
- good maintenance
- minor mechanical repairs.
Optimisation can also involve a ‘night purge’ that reduces mechanical cooling by automatically flushing a building with cool night air using natural ventilation. This reduces HVAC operating hours and plant load.
For more HVAC optimisation and maintenance strategies, see the NSW Government’s HVAC optimisation guide.
Upgrading to a more efficient HVAC system can deliver significant energy savings over its 20-25 year lifespan. Due to technological advances, there are many more efficient options available.
At the point of upgrade, assess opportunities to improve performance across the entire HVAC system. This includes the plant equipment, delivery and emission system. Overall performance is determined by the features of all 3 sub-systems and their integration.
A range of more efficient HVAC systems, some of which use passive heat transfer or low airflow rates, can halve mechanical HVAC energy use. An upgrade can also yield substantial water and trade-waste savings. HVAC systems are responsible for up to 30% of water use in commercial buildings. In more extreme climates, accurate sizing of the heating and cooling units can greatly improve efficiency. The best available reverse cycle air conditioners are 30-40% more efficient than ‘minimum standard’ models.
Some business models can address upfront cost barriers to investing in HVAC upgrades. These include energy performance contracts delivered by energy service companies (ESCOs) and ‘HVAC as a service’ business models. To read more, see the factsheet on overcoming split incentives.
Electrification of HVAC systems
Advances in electrically powered HVAC systems, such as heat pumps, can result in significant energy savings and emission reductions.
For some buildings, 100% electrification may not be viable. However, a majority of the heating load being met with electricity, paired with a small amount of fuel backup, can still result in big savings.
The savings generated from HVAC electrification can be even greater when combined with onsite renewable energy generation. To demonstrate how renewable energy technology can be integrated with HVAC equipment, the Australian Government is co-funding an Innovation Hub for Affordable Heating and Cooling (i-Hub).
To read more on opportunities and challenges for electrification of space heating, see the American Council for an Energy Efficient Economy’s research report.
Advanced rooftop packaged air conditioners
Rooftop-packaged air conditioners are becoming more common, although many operate at part load where they are less efficient than at full load.
Rooftop-packaged air conditioners can incorporate advanced features that improve part load efficiency, reliability, and reduce energy consumption by about 17%. These features include:
- 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 systems capture solar radiation by heating and storing 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 energy infrastructure and generate low or no carbon emissions. Since periods of incident solar radiation and cooling loads coincide, solar cooling reduces peak demand.
Computer technologies continue to enhance HVAC system efficiency, reliability and intelligence. They also assist integration with other building services.
Accurate and reliable measurements enable efficient HVAC tuning and operation. Intelligent controls allow post-failure assessment and can provide predictive diagnostics and maintenance advice.
Many advances in commercial building automation and HVAC control also improve indoor air quality control. The importance of fresh, clean air is understood in modern workplaces, with more emphasis on controlling dust, bacteria, odours and toxic gases.
To read more, see the Building management systems technology guide.
UV treatment of return air can deliver a high standard of air quality while reducing the dependence on outdoor supply. It also reduces fouling of fans and heat exchangers.
Chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants have a high global warming potential (GWP) and have largely been phased out in Australia. A regulated phase down of hydrofluorocarbons (HFCs) is underway worldwide as these refrigerants have high GWP. Many new refrigerants will be based on ammonia or CO2. Ask your service provider about the best products for efficiency and environmental performance.
To read more on key developments in the refrigeration industry, see the Australian Government’s Cold Hard Facts 2020 report.
The Trajectory for Low Energy Buildings - HVAC projects
Under the Trajectory for Low Energy Buildings agreed to by Energy Ministers in 2019, the Department of Industry, Science, Energy and Resources is investigating maintenance practices and performance of HVAC equipment. This will inform future work including the development of energy efficiency information resources for existing commercial buildings and retrofits.
Key findings and results of this work are available on the Better Ways to Work website.
In 2021, the University of NSW began developing energy-efficiency resources to inform decisions about commercial building upgrades. The project will consider the top 5 opportunities for energy efficiency in buildings and comparison studies on HVAC upgrades versus replacement.
Resources from the project will be available by the end of 2021.
NCC 2019 HVAC Case Study series Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH)
1200 Buildings Case Studies: Alto Hotel, 636 Bourke Street (PDF 929 KB) City of Melbourne
Energy in Buildings: 50 Best Practice Initiatives Clean Energy Finance Corporation
Green Roofs, Walls and Facades fact sheet (PDF 2.32 MB) Victorian Government
Guide to Low Carbon Commercial Buildings - Retrofit (PDF 15.6 MB) Low Carbon Living CRC
i am your optimisation guide: hvac systems (PDF 4.66 MB) NSW Government
Window Energy Rating Scheme Australian Glass and Window Association