Energy-efficient AC Systems Can Improve Singapore’s Green Building’s Performance


Singapore has yet left another striking line by crossing a major milestone of their green commitment in the September this year. The country has successfully transformed 21% of its existing building to comply with the green standardizations, namely Green Mark established by the Building Construction and Authority (BCA). The pathways towards the greener future is now looking rather bright to achieve the key targets set by the Inter-Ministerial Committee on Sustainable Development – greening at least the 80% of total buildings by 2030.

Power consumption mitigation has been one of the main highlights being emphasized in the performance of a green building, putting the application of energy-efficient technologies application on top of the priority list. A recent study on the central air-conditioning system (AC) shows that highly efficient chiller system can result in significant energy savings – however, the key for chiller operation is to know how the unit performance is aligned with the optimum design efficiency after its initial installation.


How much can an energy-efficient central AC system enhance your building performance?

The study carried out by BCA involved 17 office towers, six hotels and seven retail and commercial build­­­ings in Singapore which were all awarded Green Mark GoldPlus or Platinum certifications.

Building Type

Chiller Plant Performance (Average kW/Rton)

Office (17 projects)


Commercial & Retail (7 projects)


Hotel (6 projects)


Overall (30 projects)



All of the assessed buildings achieved a designed and verified average central AC system efficiency of 0.64kW/Rton. Several things were gauged in order to determine the system’s efficiency, i.e. the power consumption (measured in kW) and the cooling load of the buildings (measured in RTons). It is underlined that the

All the buildings under the study were achieving a designed and verified average central AC system efficiency of 0.64kW/Rton. The system efficiency was measured in terms of the power consumption in terms of kW and the cooling load of the buildings measured in RTons. The lower the value of efficiency, the more energy savings it is indicating.


Designing building’s energy efficiency

Building simulation studies using energy modelling tools during the Green Mark assessment is carried out to elicit the designed efficiency for new buildings. Upon completion, BCA undergoes a two-levels verification of which execution is firstly done at building completion, followed by one YOY operations when the cooling load for the facilities had stabilised.

The study denotes that the assessed buildings perform energy efficiency shown by a 23% of improvement on the average performance of the buildings’ AC systems, over the typical compiant system of 0.83%kW/RTon for the cases of new buildings within the period of 2008 and 2011.

With regards to the assumption of the typical weekly operating of office buildings in Singapore that can reach up to 55 hours, a cooling load of 2000 RTon and an electricity tariff of $0.25/kWh, a building operating at 0.64kW/RTon could save approximately $280,000 annually compared to if the building operates at 0.83kW/RTon.


Greening beyond the utilization of energy efficient AC systems

Other usage of green features and streamlined energy saving strategies can also achieve significant amount of energy savings in Singapore’s buildings. The table below shows the report of each assessed building with regards to its energy performance.

Building name


Green Mark Rating

Total Designed Annual Energy Savings

Design % Energy Consumption Savings

Verified Total Annual Energy Savings

Verified % Energy Consumption Savings

Tokio Marine Centre



$ 207,796.25


$ 225,161.12


9 Tampines Grande



$ 675,150.25


$ 387,913.75


Standard Chartered (Changi)



$ 405,178.75


$ 422,384


City Square Mall



$ 2,861,316.75


$ 3,133,865.31


Mapletree Anson



$ 570,649.25


$ 678,710.25



The designed energy savings are acquired through building simulation studies with energy modelling tools during the Green Mark assessment. Meanwhile the verified energy savings are based on the actual energy consumption data collected upon the building operation over at least its first 1 year.

In five out of the six notable cases, the buildings are even performing better total energy savings during operation than they were initially designed. The study eventually concludes that the combination of energy-efficient AC systems and other green features could at least save 30% and 25% of overall energy for Platinum buildings and GoldPlus buildings, respectively. (AGB – SA)


The above insight is reported in this feature with regards to the information provided by the Building and Construction Authority (BCA) during the International Green Building Conference 2013.

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