While buildings are being developed with ever greater energy efficiency in heating and air-conditioning systems, there is still much to be gained from better communication between building designers and clients. Rita Mu reports.
In the past decade, as architects and builders have taken more sustainable building approaches, industry bodies like the Australian Institute of Refrigeration, Air- Conditioning and Heating (AIRAH) have been helping to drive change by providing training and education in the design and implementation of energy efficient Heating, Ventilation and Air- Conditioning (HVAC) systems.
Despite this, there remains a lack of communication between building designers and clients about how the effectiveness of HVAC systems can be optimised, and thus help improve the health and wellbeing of building owners and occupants, save on energy costs and reduce greenhouse gas emissions.
Mechanical engineer at Arup, Gerard Healey, says the extent to which HVAC systems are discussed between building designers and the client varies and ultimately depends on the project and people involved, but, in general, it could do with improvement.
"If it’s a rigid structure, you might only be able to talk to the person who is one step up from you and so in those instances, it can be really hard to have a good conversation with the client about what the implications or opportunities are with making the HVAC systems more efficient,” he says.
“I don’t see much downside from the client being better informed about what the implications, risks or opportunities are. While the reality is that in some cases it happens better than in others, it’s certainly something worth striving for.”
Regardless of whether there is a communication gap or not, Healey says, finding simple ways to reduce the demand for heating, cooling or ventilation is fundamental.
“The best thing to do is try to reduce the amount of heating, cooling or ventilating you need to do in the first place, because this will then reduce the amount of energy you need to use to control the conditions of the building,” he says.
“This can include things like putting insulation in the building to keep heat in or out and placing shading on windows to keep direct sunlight out.”
According to Healey, environmental sustainability star rating systems can provide building designers and their clients with an incentive to work towards energy efficient HVAC systems. But it is important to be clear about what rating systems will be targeted, he says, as there are various types.
The most notable rating systems in Australia which take into consideration a building’s energy efficiency include the Green Building Council of Australia’s Green Star and the National Australian Built Environment Rating System (NABERS), managed by the New South Wales Office of Environment and Heritage.
The NABERS environmental rating system, for existing commercial and residential buildings, now operates on a six-star rating scale. A six-star rating was introduced in August 2011 and represents a 50 per cent reduction in greenhouse gas emissions or water use from a five star rating.
Buildings with six-stars demonstrate ‘market leading’ performance.
According to engineering manager, Peter Kinsella, of AE Smith & Son, simple design elements such as the orientation of the building will help improve the effectiveness of HVAC systems.
“The orientation of the building, particularly the size and orientation of glazing, and the use of permanent or adjustable shading has a great impact on energy requirements,” he says.
The materials used for HVAC systems should also be carefully considered, says Kinsella, as they can have a significant impact on the thermal performance of the building envelope.
“Generally speaking, the higher the thermal resistance, or R-Value, the less heat is gained by the building during the summer months and the less heat is lost by the building during winter, meaning that building services do not need to provide so much cooling in the summer or heating in the winter,” Kinsella explains.
“Increasing the R-Value of a wall, roof or floor is usually achieved by increasing the insulation added to construction…Besides the insulation material, the introduction of an air gap or a reflective foil layer can also produce significant improvements.
“In the case of a residential building, the use of double glazed windows in place of single glazed can halve the rate of heat lost through the window.”
Keeping it simple So as industry moves to more sustainable approaches to designing buildings, is it better to opt for simple or complex HVAC systems?
According to Kinsella, the general rule of thumb is to keep it simple.
“A complex project may be an excellent design on paper and have the ability to be very energy efficient, but if the detailed design is not in alignment with this, or the construction, commissioning, maintenance, or operation are not carried out diligently, the result can be a very poor performing building,” he says.
“Most buildings can go through considerable change during their lifetime and so buildings likely to pass through several structural changes, changes of use, and changes of management could be better served by a less complex and more robust system.”
In 2006, a range of energy efficiency measures were introduced in the Building Code of Australia (BCA). Last year, these measures were made more stringent to include a range of requirements for building designs, including increased thermal performance and the implementation of a number of ways to reduce air leakage.
According to Kinsella, the BCA has raised the bar in energy efficiency substantially.
“I think that almost everyone is interested in improving the energy efficiency of their HVAC systems and there are some items that can make significant improvements at very little cost, but major changes to the HVAC system can come with a substantial price tag and need to be budgeted for,” he says. “If the building is operating quite well and there’s no pressing requirements to change things then it can be hard to justify these costs, but it would be advantageous to have a clear plan of improvements and to take the opportunity of any renovation works to implement them.”
