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Singapore’s Zero Energy Building Retrofit

Credits: ©2011 BCA Zero Energy Building

A massive array of solar panels of 1,300 sq metres [14,000 square feet] - almost half a football field and the biggest such installation in Southeast Asia - covers the roof of the Zero Energy Building in Singapore. The solar photovoltaic power panels can generate about 207,000 kilowatt-hours (kWh) of electricity annually. Three hours of sunlight would be enough to supply the building's energy requirement for a day. At night and when there is no available sunlight, the building can tap energy from the grid. This building is also certified under Singapore’s Green Mark certification program for green buildings. The Singapore government has a goal to have 80 percent of all buildings on Green Mark certification by 2030. Other green features include floor diffusers supply cool air which, once warmed, will rise to vents in the ceiling to be removed from the building, more energy-efficient air-conditioning system that detects carbon dioxide levels and lowers fan speed when fewer people are around, and personalized ventilation that allows air-conditioning around each desk to be adjustable according to individual needs. Additional building features include innovative green technologies such as sunray collectors and mirror ducts, green shading, solar chimneys and solar panels, coated glass for heat reduction, cool paint and cool pavement coating. The ZEB is expected to be about 40-50% more efficient than similar office buildings. Although connected to the grid, the building is expected to generate as much electricity as it consumes over a typical year.


Singapore Zero Energy Building PVs

Singapore's Zero Energy Building by the Building & Construction Authority includes three generations of photovoltaic systems: 1G, 2G and 3G that contribute to the generation of all power on-site. ©2011 Building and Construction Authority of Singapore

Read Case Study by Yudelson Associates

Zero Energy Building at BCA Academy
Zero Energy Building (ZEBs) refers to buildings that achieve net zero energy consumption annually through the incorporation of renewable energy sources in the buildings that provide all power for the building’s uses. Singapore’s ZEB project is a showcase and test-bed innovative building that is unusual for an existing building renovation. The ZEB at Building Construction Authority (BCA) Academy was the first building in Southeast Asia (as of 2009) to be fully retrofitted with green building design features and technologies. The building achieved the BCA Green Mark Platinum Award, the highest award accorded to environmentally sustainable development in Singapore. 

The project involves retrofitting an existing building to serve as BCA’s Academy, which houses offices, classrooms, a library resource centre as well as a visitor centre. It is designed to be 100 percent powered by solar energy. Photovoltaics provide 1,540 m2 of solar panels that are installed on ZEB’s roof and other prominent areas. These PVs generate about 207,000kWh of electricity annually - enough power for 45 four-room apartments/flats. The building also incorporates advanced green building technologies such as personalized cooling for occupants, integrated façade devices to shade the building and bring daylight to the interior and vertical greenery to reduce solar gains and glare.

The main objective of the project is to demonstrate that the concept of a ZEB is possible for low buildings even in the tropics, where high air-conditioning loads typically constitute more than 50 percent of the electricity consumption of buildings. The target has been achieved since the building was completed in 2009. In fact, the building has generated a surplus of electricity - enough surplus electricity to power 35 five-room apartments in a year.

The ZEB project is a collaborative research and development (R&D) effort between BCA, the National University of Singapore, the Solar Energy Research Institute of Singapore and partners from the private sector, DP Architects, Beca Carter and Davis Langdon & Seah. It received R&D funding from the Ministry of National Development (MND) Research Fund for the Built Environment and the Singapore Economic Development Board’s (EDB) Clean Energy Research Test-bedding (CERT) Programme. As part of EDB’s CERT Programme, the ZEB will be used as a test centre for clean energy technologies.

The building received the IES Prestigious Engineering Achievement Award from the Institute of Engineers Singapore, and has been recognized as an Outstanding Achievement Project, in addition to the MND Minister's Team Award for Singapore Green Building Week and Zero Energy Building, BCI Green Design Award (Green Leadership Award - Institutional Architecture) and The Aspen Institute Energy and Environment Award (Government Award). This Zero Energy Building was one of the first buildings to fulfill the government of Singapore’s ambitious plans in terms of green building: Singapore plans to make 80 percent of all buildings in the island state green by 2030.

Energy Efficient Envelope • Low-e glass - unlike normal clear glass, it has a special low emissivity coating. This increases the energy efficiency of windows by reducing the transfer of solar radiation through glass.

• Shading devices - with strategically placed shading devices, there is a significant reduction of solar heat gain and improvement of the quality of natural lighting within ZEB.

Lighting System Using various features such as energy efficient lamps, automatic switching via photosensors and daylighting, there is a marked reduction in energy required for artificial lighting within ZEB.

Active Control and Management The ZEB has an advanced Building Management System to control, monitor and manage all the equipment installed in the building. With close monitoring of usage and occupancy patterns, energy use can be optimised while maintaining comfort and functionality.

Air-Conditioning System Through technologically advanced chillers, variable speed drives, and personalised ventilation systems, there is about 40% reduction in energy required for the air-conditioning of the building.

Fully Powered by the Sun All three generations (1G, 2G & 3G) of photovoltaic systems will be installed to harness energy from the sun to generate electricity and power all the appliances and lighting in the ZEB.


• Cells made from silicon wafer

• Types: monocrystalline silicon, polycrystalline silicon

• High efficiency and requiring less surface area to generate electricity but more expensive to manufacture

• Suitable for rooftops and integration into building façade and skylight


• Thin-film deposits of semiconductors

• Types: amorphous silicon, copper indium selenide/sulphide

• Flexible, lightweight, less silicon intensive and aesthetically pleasing

• Suitable for rooftops and integration into building façade and skylight


• Departure from 1G and 2G which are silicon-based technologies, promising new approach currently under commercial development

• Flexible, lightweight and aesthetically very pleasing

• Types: Dye-sensitised solar cells, polymer solar cells, photo electrochemical cells, nanocrystal cells

• Suitable for integration into building façade and skylight

Natural Daylighting and Ventilation Systems

Mirror Ducts
A simple system that uses ducts made of a highly reflective material to bring natural light into the space, enabling a considerable energy natural light, enabling improved energy consumption. There are no mechanical parts involved and no power is required.

Mirror ducts capture zenith daylight (which is brighter than lateral daylight) through external collectors. Light is channeled into horizontal reflective ducts within the false ceiling which then exits through the ceiling apertures above a user, into the workspace below. Such light is usually glare-free.

Daylight level across the building depth is more even. Three types of mirror ducts are tested for their reflectivity and effectiveness. These are reflective aluminum alloy with a visible light reflectance (VLR) of 98 percent; mirrored acrylic with VLR of 80 to 90 percent; and optical grade polycarbonate with 99 percent VLR for light rays within zero to 27.5 degrees.

Light Shelves
Light shelves are highly reflective surfaces that reflect daylight deep into interior spaces including the library, L3 offices and the experimental office. This can help to reduce the use of artificial lighting at daytime. The efficiency of the light shelves in ZEB is enhanced using ceiling material that has a highly reflective coating on the surface. Light shelves also provide shade against direct sunlight.

Light Pipes
The system of light pipes in the experimental office is comprised of a pipe that sticks out of the building's roof and reflects sunlight directly into the interior. Light pipes are more energy efficient than skylights because less energy escapes from the interior due to less surface area.

There are two types of light pipes in ZEB. One type of light pipe is equipped with a rotating mirror that is located in open area while the other type does not have a rotating mirror.

Shading Devices
Sunshade devices minimize direct sunlight into the building interior, which reduces solar gain on the façade without compromising daylight and natural ventilation. In addition to providing shade, the sunshades surfaces exposed to direct sunlight are each installed with thin film amorphous photovoltaic panels. One square meter of PV panel can generate power for about one 45-Watt light bulb. Hence, the total PV installed on the shading devices is able to power 24 nos. of such light bulbs.

Glazing Testing Chambers
Four types of glazing are being studied for their dynamic performance (glare, solar control and visibility), including:

Electrochromic glass is glazing that changes its opacity depending on the amount of sunlight being received. It is being tested for its light and heat control.

Photovoltaic glass has a dual function of providing shading and generating power at the same time on this building. It is being tested for its efficiency, impact on view, shading, heat absorption and re-radiation.

Double Glazed Unit (DGU) with internal operable glass is being studied for its impact on view, shading and heat absorption. Each unit consists of blinds between the glasses which can be turned up during strong sunlight.

Clear DGU glass is used as a baseline reference for comparison. The air between the double sheets of windows is thoroughly dried and the space is sealed air-tight, providing superior insulating properties and eliminating possible condensation. Double glazing is used in all air conditioned areas. Single glazing is used in the classrooms and school hall.

Solar Chimneys
The core concept of the solar chimneys also known as solar assisted stack ventilation system - revolves around the use of heat removed from solar panels to induce ventilation in the L1 and L2 classrooms, as well as the L3 school hall (buoyancy effect).

Heat is built up below the solar panels when it is working. A 300mm gap is allowed between the solar panels and the metal roof to allow ventilation which is essential to ensure efficiency of the solar panels. Heat in the gap is also a good source to produce buoyancy effect which is the effective operating principle for natural ventilation in the school hall and classrooms.

Since the indoor space of the school hall and classrooms is linked with the gap by channels, when heat is removed from the gap, air flows into the air channel due to the negative pressure in the solar panel roof gap. To keep the proper pressure balance in the rooms, outdoor fresh air is induced through the windows.

Dark color metal ducts or solar panels are used to construct air channels to further enhance heat removal (stack effect). Several chimneys are placed on the roof and extraction fans are installed in each chimney to provide the extraction when stack effect is not functioning.


  Singapore Zero Energy Building Brochure (8,520 kb)

  Singapore Zero Energy Case Study (1,953 kb)


Singapore Zero Energy Building Website

Green Building Product Certification (Singapore)

BCA Green Mark (Singapore)