After a few iterations to define
the benefits of electricity genera-
tion with PV versus energy sav-
ings through solar chimneys, roof
greening or reflective coatings, a
PV system of 190 k Wp capacity
covering some 16,577 ft2 (1540
m2) was chosen. A large grid-con-
nected system designed to produce
a maximum electricity yield was
installed on the roof. Therefore, a
performance-based invitation to
bid was launched. The supplier
had to guarantee a certain amount
of electricity production, which
provided motivation to install as
well as operate and maintain the
PV system efficiently.
PV was also installed in the
façades, designed here to demon-
strate the variety of PV technologies
and their multifunctionality, such
as serving as sunshades, railings,
opaque and semitransparent walls
Those smaller systems were off-
grid, meaning their dc electricity
was consumed on the spot by a cell
phone charger. Both grid-connected
and off-grid systems are owned
and operated by the BCA, follow-
ing the requirements for electrical
power systems set by Singapore
Energy Market Authority (EMA)
and the design guidelines on con-
servation and development con-
trol by the Urban Redevelopment
The BCA retrofit project was
intended to demonstrate efficient
use of energy in a retrofit building.
Shading devices, lightshelves, vertical green walls, high-performance
glazing, and lightweight wall systems
are integrated in the west façade.
Light pipes and ducts are installed
on the roof and east façade. The roofs
are covered with large PV systems
to generate enough electricity for the
building to become net zero. Parts
of the roof have solar chimneys for
improving the air movement within
the naturally ventilated spaces.
This article benefited from data supplied
by Dr. Nirmal Kishnani from the National
University of Singapore and Selvam Valliappan
from the Solar Energy Research Institute of
Singapore, and from Prof. Wong Nyuk Hien
from National University of Singapore for the
Building and Construction Authority of Singapore. 2014. “Leading the Way to Net Zero,
2009-2014: Inside SE Asia’s First Retrofitted
Zero Energy Building.” http://www.csb.sg.
Cheong, D., et al. 2013. “An energy-efficient
air-conditioning system for better indoor quality
in the tropics.” Urban Sustainability Congress.
Garde, F., et al. 2014. “A review of 30 Net
ZEBs case studies worldwide.” A report from
IEA Joint SHC Task 40/ECBCS Annex 52:
Towards Net Zero Energy Solar Buildings,
Grobe, L.O., et al. 2010. “Singapore’s Zero
Energy Building’s daylight monitoring system.”
International Conference on Applied Energy.
Kishnani, N. 2012. “Greening Asia: Emerging
Principles for Sustainable Architecture.”
Lee Siew Eang. 2014. “The design, development and performance of a retrofitted net zero
energy building in Singapore.” High Energy
Lynn, N., et al. 2012. “Color rendering properties of semi-transparent thin-film PV modules.”
Building and Environment 54.
Tan Yong Kwang, A., et al. 2012. “Natural ventilation performance of classroom with solar
chimney system.” Energy and Buildings 53.
Wittkopf, S., et al. 2010. “Ray tracing study
for non-imaging daylight collectors.” Solar
Energy 84( 6).
Wittkopf, S., et al. 2012. “Analytical performance monitoring of a 142.5 k Wp grid-connected rooftop BIPV System in Singapore.”
Renewable Energy 47.
Wong Nyuk Hien, et al. 2011. “Performance
of greenery systems in Zero Energy Building
of Singapore.” International Conference on
Sustainable Design and Construction. •
ABOUT THE AUTHOR
Stephen Wittkopf is professor of architecture at the Lucerne University of
Applied Sciences and Arts, Switzerland.
Building Owner Building and
Construction Authority of Singapore
Architect DP Architects Pte Ltd
Principal Investigators for Green
Building Technologies, Environmental
Design and Energy Modeling
National University of Singapore
ACP Construction Pte Ltd
Project Manager, Mechanical & Electrical
Engineer, Civil & Structural Engineer
Beca Carter Hollings & Ferner (S. E.
Asia) Pte Ltd
Langdon & Seah Singapore Pte Ltd
Grenzone Pte Ltd
Six external scoops on the eastern facade
collect zenithal daylight and redirect it into
horizontal light ducts for daylighting of