AIRAH conference 2010, Melbourne – 30 September 2010 – If there was a key theme at the Australian Institute of Refrigeration Air Conditioning and Heating, conference, held in September in Melbourne, it was just how critical good facilities management is for achieving energy efficiency in buildings.
This is seemingly obvious, but something that time and again is neglected once buildings are designed, fitted and handed over, said the engineers and sustainability consultants who spoke at the Achieving the green dream – tomorrow’s technology today conference. And that means in practice buildings are rarely operating as they should be, no matter how much whiz bang technology they might contain.
According to managing director of Exergy Paul Bannister, getting the controls right in a building is absolutely critical.
“I spend a lot of time controlling buildings and controls are a 2 to 2.5 Star [NABERS] issue. Controls really are it, ” Dr Banister said.
AA3 building Charles Sturt University, Albury
In the academic offices building on the Charles Sturt University Albury Wodonga campus, AA3, Dr Bannister worked with designers to create a building that would require very little supervision and without complicated technology. He described the project as “one of the most exciting and most frustrating projects” he’d been involved in with all sorts of problems in delivery.
“This building was done on raw design, not technology. Albury doesn’t have a high level of services available to maintain the building so it was important to keep things simple and robust,” he said.
The design team’s brief was to create a building that must be appropriate to Albury’s climate – very hot and dry in summer and very cool in winter – and that made use of passive elements, including natural ventilation, in preference to active airconditioning systems. It was a climate in which evaporative technology made sense, Dr Bannister said.
The aim was to achieve 5 Star NABERS rating or above. The result was much better – the building is targeted at 70 per cent higher efficiency than 5 Star NABERS and has received a 6 Star Green Star Office design. It is also on track to achieve around one third of the greenhouse gas emissions (24 kg/ square metre) of a best practice 5 Star NABERS office building (71 kg/sq m).
The two-storey building achieved low energy use primarily through its high thermal mass, enhanced by the use of a change phase material. This wax-like material, called Micronal®, was embedded in plasterboard fixed to the underneath of the ceiling slabs and in the concrete floor screed. It came in two forms, said Dr Bannister – a substance like milk that is poured into the screed and like sand when it is incorporated into plasterboard.
Insulation in the building was double that required under the building code and all windows were double-glazed.
The change phase material melts at around 23 degrees centigrade and as it is melting absorbs the latent heat from the plasterboard or cement screed. This has two effects, said Dr Bannister. Firstly it enhances the slab’s ability to remain cool and secondly the surface temperature of the floor or ceiling is kept at the melting temperature while latent heat is absorbed.
“Hence there is the unusual effect that as heat is transferred from the office space to the building fabric the temperature of the fabric stays constant and cool thus holding down the operative temperature even if the ambient air temperature increases.”
While most of the building’s temperature control is achieved passively, a hydronic heating and cooling system is used to remove excess heat in summer and provide extra heating in winter. In the months between these seasons the building “cruises because of its mass.”
Heat is removed from the building by a conventional hydronic in-slab system with the water being cooled by a cooling tower that mostly runs during the night. In winter heating is provided by a condensing boiler, which only needs to be relatively small because of the high thermal mass of the building.
The final handing over of the building had been a disappointment, Dr Bannister said, with a management change in the university resulting in the design team not seeing the building for 18 months. The choice of pumps, valves and hydraulic system was different to the initial design and maintenance is a potential issue. The building has not been fine tuned as yet and the building management system and extra temperature sensors in the slabs have not been connected.
“The building is tracking 5 Star plus 40 percent – pretty good considering it hasn’t been tuned. Ultimately it only has a few pumps so there really is a finite amount of energy that can be used,” Dr Bannister said.
“We wanted to achieve a building that most of the time does nothing. We’ve achieved that. It has been a bit disappointing in the follow through but academic institutions are very busy organisations. The nice thing is we built something that is not very expensive and that works pretty well with very little supervision. ”