When American Willis Haviland Carrier conceived of a machine that could control not only temperature but humidity too, he could never have foreseen his invention would irrevocably change our buildings and the lives of the people within them. With less need for openable windows, buildings could be constructed with larger floor plates. At the same time, air conditioning led to productivity increases as office workers could work through long, hot summers without raising a sweat.
But while air conditioning technology solved many problems, it brought with it some new ones. In his book, Losing our cool: Uncomfortable truths about our air-conditioned world, Stan Cox argues that society is paying a steep price for our air conditioning. We stay inside longer, exercise less and get sick more often – and, of course, the electricity required to keep our buildings icy-cold is contributing to global warming.
As air conditioning has made the leap from a luxury to a necessity, its use is ensuring its future use. The more we use air conditioning now, the more it contributes to climate change, hotter summers and even greater demand in the future.
However, recent innovations in heating, ventilation and air conditioning (HVAC) technology are looking at ways of improving energy efficiency, and in turn delivering significant financial advantages and environmental benefits.
Smart, sustainable cooling concepts should be considered in conjunction with other good, green design principles. Simple passive design techniques that assist in controlling ventilation and the temperature of a building, without the use of any mechanical systems, should form the basis of building design and retrofit work. Reductions in energy needs can be achieved through site orientation, window glazing and shading, good thermal mass and insulation appropriate to the climatic conditions. Features such as these can enable mechanical HVAC systems to be downsized. In essence, the better the building façade, the less energy required inside.
While traditionally most of the focus on HVAC has been on minimising its energy consumption, the Green Star rating system for buildings takes an holistic approach to HVAC, assessing the amount of fresh air delivered into a space, the mix and circulation of the air, the quality of the air being circulated, and the capacity of the building to deliver the air effectively, all of which can affect the wellbeing of occupants.
The design and construction of an HVAC system is also considered within a number of Green Star tools. In Green Star – Healthcare v1, for instance, access to the ducting for maintenance purposes is assessed, as is the construction of the system. In Green Star – Office Interiors v1.1, projects are required to clean the existing ductwork prior to use in order to reduce the amount of mould in the system itself.
All Green Star rating tools measure the proportionally large environmental impact of a refrigerant’s ozone depletion potential (ODP) and global warming potential (GWP) - as a refrigerant molecule might contribute 1,000 times more to climate change than a molecule of carbon dioxide, for example. Furthermore, the water use of an HVAC system is considered if the system uses a cooling tower, as well as the risks that such systems pose with regards to Legionella.
Innova21, the University of Adelaide’s new building for the Faculty of Engineering, Computer & Mathematical Sciences, boasts an array of HVAC innovations which will not only reduce the environmental impact of the building, but help improve learning outcomes for students.
The eight-storey building was awarded a 6 Star Green Star - Education v1 rating in May 2010, representing ‘world leadership’ in environmentally sustainable design.
Innova21 features a natural gas-fired tri-generation plant which supplies all of the building’s electricity, heating and cooling requirements and will reduce peak electrical demand by around 60 per cent compared to ‘business as usual’. Due to local planning laws, the plant has been designed to run in ‘island’ mode, which means it is isolated from the grid. This posed a number of design challenges but was deemed worthwhile due to the significant operational, environmental and life-cycle savings offered by the plant.
Tri-generation installations typically convert around 75 to 85 per cent of the energy source into electrical power and useful heat. This compares favourably with conventional power generation which has a typical delivered energy efficiency of only around 30 to 35 per cent. This is particularly important in South Australia where the majority of power is generated by coal-fired power plants.
Costs for the plant were further offset by reducing the need for traditional plant infrastructure such as back-up generators and separate boilers and chilling units. Innova21 also gained a ‘green tick’ for the 500,000L water tank which harvests water from around the campus for use in the building’s cooling towers and toilets.
Another stand-out feature of Innova21 is the innovative use of the building’s foundation piles for geothermal energy storage. This system uses the thermal mass of the earth beneath the building to provide an efficient source of cooling for the building after hours.
The system involves reticulating chilled water, produced by the building’s tri-generation plant, through pipework embedded within the foundations. This cools the ground, and in effect enables the building to ‘store’ energy to cool areas, such as data rooms, after hours, when the tri-generation plant is turned off. Cooling the building in this manner is more efficient as it allows most cooling potential to be produced using the tri-generation plant’s absorption chiller, which uses waste heat to produce chilled water, rather than less efficient electric chillers. The use of geothermal energy storage is an Australian first and is calculated to reduce the building’s cooling-related CO2 emissions by 58 per cent.
Innovative cooling systems aren’t just the preserve of new buildings. Norman Disney & Young’s Melbourne office at 115 Batman Street is the first refurbished building to achieve certification under all three Green Star Office rating tools. The project, which has transformed a derelict factory into a state-of-the-art multi-storey office block, achieved a 5 Star Green Star rating under the Office Design and As Built v2 rating tools, as well as a 5 Star Green Star Office Interiors v1.1 rating. The building now accommodates the entire Melbourne team of consulting engineers, and is a strong symbol of NDY’s commitment to a sustainable future.
Within the building, a passive chilled beam system is used for ground, first and second floor air conditioning. Chilled beam technology works via convective cooling, where warm air rises and is cooled by the chilled beam pipework in the ceiling panels and then falls back to the floor. The process is more efficient than air-based cooling in drier climates and also eliminates the effects of draughts that may occur with conventional air conditioning systems. NDY’s system ensures the space is comfortable and operates well in extreme conditions.
The bottom line for facility managers is this: the efficiency of HVAC systems has improved significantly over recent years. Replacing an existing HVAC system with a newer model may help you to deliver significant energy savings. However, if capital costs are an issue, consider how you may improve existing equipment through tuning and installing advanced control systems.
Air conditioning should not be considered a ‘bad’ practice. It can be an effective solution for cooling and ventilation needs, provided it is considered as one element in a range of solutions, rather than the starting point for building design or operation. Smart passive design features should be at the forefront of design considerations, not an afterthought. From time to time, even with the right aspect and natural ventilation, some artificial assistance may be required. In cleverly-designed green buildings, the air conditioning and heating won’t need to work as hard – which means less energy and greenhouse gas emissions, and more dollars in the bank.
One final note about air conditioning and the important role facility managers can play in maintaining indoor environment quality and occupant comfort. In an analysis of over 6,000 office workers’ complaints in 34 Australian buildings over two years, researchers at the Investa Sustainability Institute have found that gripes about being too hot, too cold, too stuffy or too draughty are most frequent on Mondays (25 per cent of all complaints) and fall dramatically throughout the week (down to 14 per cent of all complaints on Fridays).
In some buildings, the air conditioning system may be switched off over the weekend, reducing energy costs and emissions. However, this means that the air and the materials in the building heat up over a summer weekend and cool down during winter. At the same time, people have been in their homes all weekend and have become accustomed to being either in a space set to their own personal comfort level or able to dress in accordance with their surroundings. So, when they arrive at work on Monday, it’s easy to blame their lack of motivation on the air conditioning; by Friday the building may be more in balance and the people within it are looking towards the weekend once more. Facility managers have an important role in making sure that buildings can be not only cost-effective, but productive, spaces throughout the week – and throughout the year. Visit Investa’s Green Buildings Alive website (www.greenbuildingsalive.com.au) to find out how you can diagnose Monday-itis in your office.