A second case study from the Australian Institute of Refrigeration Air Conditioning and Heating, conference, held in September in Melbourne, on the theme of just how critical good facilities management is for achieving energy efficiency in buildings.
AIRAH 2010 conference, Melbourne – 30 September 2010 – Another project that highlighted the importance of co-operation between designers, builders and facilities managers was the refurbishment of Northbank Plaza at 69 Ann Street in Brisbane. Refurbishment of the 30 year old building was completed to a Property Council of Australia A Grade standard and NABERS Base Building 4 Star Commitment Agreement in 2009.
Connan Brown, Senior Associate and ESD Manager with Norman Disney & Young, told delegates it was the client’s contractual arrangements with the builder and the builder’s back-to-back requirements of subcontractors as well as novation of the designer that provided the motivation to smooth out technical issues on the building.
This was achieved through a contractual agreement between the building owner and builder specifying the building had to achieve a guaranteed NABERS rating of 4.5 Stars on completion.
The performance of the building was established through an energy modelling report in accordance with very specific NABERS guidelines that assess the forecast energy consumption best case and also a number of “off-axis” scenarios. This report must then be viewed by an experienced NABERS and energy modelling specialist.
An off-axis modelling scenario, said Mr Brown, assumes that one or more design assumptions does not actually occur, or the control routines have failed in one or more ways.
Mr Brown said the commitment agreement worked well to ensure the building performed as it was designed to and that all work was of the highest quality.
The building owner, Charter Hall Group, selected a Tier One builder (Watpac Specialty Services) which then selected highly experienced subcontractors who were required to back up the builder’s guarantee.
The mechanical contractor with its controls subcontractor took up the risk associated with delivery of the commitment agreement. The design/energy modelling consultant was novated to the builder, which meant the builder and subcontractors scrutinised the energy modelling report very carefully.
The contractual obligation to deliver the rating and complexity of both the energy model and the interactions of key equipment meant that documented minimum energy efficiency levels needed to be followed closely. All equipment submissions were reviewed in terms of both quality and energy efficiency by the building services designer and the energy model updated to reflect the selected equipment, said Mr Brown.
Architects for the project were Brisbane based firm Cottee Parker. NDY was responsible for design and energy modelling for the project and facilities manager was Colliers International.
“We worked together to solve issues. We couldn’t blame the tenants or other factors for the building’s performance – we had to fix it,” Mr Brown said.
A critical factor in the project was ambient relief provided by the chiller, which meant chiller selection and fine tuning was particularly important, said Brown.
“Ambient relief is very powerful and a lot of modelling is not showing that. Be careful with chiller selection – chiller technology has changed a lot and modern chillers are excellent with ambient relief.
“But fine tuning is critical in the delivery of low energy in practice.”
It was essential that chiller staging control was reliable so backup sensors were a good idea.
The refurbishment of the 30 year old building included replacing the three original chillers with new high-efficiency centrifugal chillers as well as an additional cooling tower to provide four equal sized towers. All air handling units were replaced with new purpose built Variable Air Volume, VAV units and swirl diffusers were installed to improve performance and occupant comfort.
All office lighting was replaced with T5 low brightness louvred fittings, which are expected to reduce energy use by 60 per cent. In addition all common area lighting was replaced with energy efficient fittings and intelligent lighting control.
Lifts were modernised and provided with energy efficient drives. The building management system was also upgraded to suit the new equipment.
But it was the clear contractual arrangement that really ensured the building achieved its operating performance of 4.5 NABERS rating, Mr Brown said.
“While there are real and fair criticisms of contracts requiring guaranteed NABERS ratings the strong contractual arrangements did focus attention on resolving issues rather than focusing on mitigating factors such as the unusual weather, unusual tenant behaviour and any limitations of modelling software.
“The value of having clear binding energy targets common to the facilities manager, installation and maintenance contractors, builders and designers should not be underestimated.”