Sunrise Square is a newly proposed commercial building, aimed to secure the BCA Platinum Green Mark award, to be completed by October 2015. The building is fully air-conditioned except for some common areas and it has a multi-storey carpark which is to be naturally or mechanically ventilated. The air-conditioning system for the building is water cooled chilled water system. The cooling load of the system is greater than 500 RT.
The purpose of this project is to recommend the building owner and the design team on developing the right strategies and presenting cost effective measures for the energy efficient component to secure the Platinum award.
2. Areas of Emphasis
To achieve the award, the building must encompass the BCA pre-requisite requirements and a set of other green factors. This report will focus on attaining all components of the energy efficiency segment.
3. Energy Efficiency
3.1 Thermal Performance of Building Envelope - ETTV and Building Envelope- Design/Thermal Parameter
According to the award guidelines for air-conditioned building, the ETTV computed in the Code of Envelope Thermal Performance should be 40W/m². The building also needs to demonstrate a minimum of 30% energy savings.
As for the Building Envelope, it is necessary to minimise a west-facing façade and west-facing windows. The sunshading provision for west-facing windows should have a minimum shading of 30%. The U-value of walls facing the west should be 2W/m²K. Finally, ensure the U-value of the roof does not exceed 1.5 W/m²K.
ETTV is affected by three factors, namely- Building materials, amount and type of glazing and the building orientation.
3.2.1 Building insulation materials
Building insulation materials are used to reduce heat transfer to achieve thermal comfort with reduced energy consumption. They may be grouped by its composition, by its structure, or by its heat reduction function (conductive, radiative, and convective). Another type would be a thermally reflective surface called a radiant barrier that is added to a material to reduce heat transfer. These materials should also have a high thermal mass which absorb energy more slowly and then hold it longer, effectively reducing indoor temperature fluctuations and reducing overall cooling requirements
High thermal mass materials include concrete, bricks and tiles; lightweight materials such as steel and timber have low thermal mass and store very little heat energy.
Concrete usually have a U value of 0.18 and can be purchased from Island Concrete Ltd.
3.2.2 Amount and type of glazing
Double glazed windows contain sealed units which are made from two panes of glass. These have a gap between them are filled with Argon gas, and they help reduce cooling loads in HVAC, reducing operation costs.
Low-emittance (Low-E) coating is a microscopically thin and transparent layer deposited on a window to reduce the U-value by suppressing radiative heat flow. Coating a glass surface with Low-E material and facing that coating into the gap between the glass layers blocks a significant amount of radiant heat transfer, thus lowering the total heat inflow. Since it is transparent to light, the amount of daylight is maximised in the building, reducing the amount of artificial lights to be installed, thus having high energy savings as well.
Hence, it was recommended to install the Double glazed with Low solar gain Low-E glass which has a U-value of 0.25 from Century Custom Windows.
3.2.3 Building Orientation
To reduce solar heat gain, minimize the direct west and east facing façade through the building orientation design.
The building can be designed to orientate 45oN of W which exceeds 22.50N of W and hence the façade is not considered as west facing façade in the computation.
3.2.4 Minimise west-facing windows
The building design should restrict...