ASHRAE Journal - May 2014 - 16
Technical FeaTure
Figure 1: Infosys SDB-1
Hyderabad. Half of the building has
radiant cooling and half has VaV
cooling.
VAV vs. Radiant
Side-by-Side Comparison
By Guruprakash sastry and peter rumsey, p.e., Fellow ashrae
Infosys, one of India's top three software companies, implemented a program
in 2011 to find the best way to cool its buildings, while creating lower energy
buildings that better suited the needs of its employees. The resulting building,
Software Development Block 1 (SDB-1) in Hyderabad, not only became the first
radiantly cooled building in India, but also resulted in the world's largest HVAC
side-by-side comparison.
The SDB-1 building includes two cooling systems. Half
of the building has an optimized variable air volume
(VAV) system. The other half has a radiant cooling with
dedicated outdoor air system (DOAS). The building was
highly instrumented to measure the impacts of the two
systems. After two years of operation, the radiant system
has used 34% less energy as compared to the VAV system.
The cost of the radiant system was slightly lower than the
VAV system and comfort surveys found improved thermal satisfaction with the radiant system.
The Idea
The SDB-1 building was designed with an envelope that
minimizes heat and solar loads, while allowing fully daylit office spaces. The result is a building that has insulated walls with thermal breaks as well as an exemplary
sun shading system. The directive for the sunshades was
straightforward. The sunshades and lightshelves needed
to provide for 95% daylight autonomy with no direct
sunlight entering the building. Daylight autonomy is the
percent of the year that a space can be fully daylit during
working hours.
As a consequence, the floor plate of the building
needed to be relatively narrow and lightshelves that
doubled as sun shades were used throughout. The
detailed daylight model verified that no internal shades
were needed in the space since glare from direct sunlight was designed out of the building. Overall, the window-to-wall ratio is 30%. However, as a visitor recently
observed, the SDB-1 building feels like a building with a
much higher window-to-wall ratio because of the lack of
blinds and the quality of the building envelope design.
Guruprakash sastry is a regional manager of Infrastructure and Green Initiatives at Infosys. peter rumsey, p.e., is founder of point energy Innovations.
16
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ASHRAE Journal - May 2014
Table of Contents for the Digital Edition of ASHRAE Journal - May 2014
Contents
ASHRAE Journal - May 2014 - BB1
ASHRAE Journal - May 2014 - BB2
ASHRAE Journal - May 2014 - Cover1
ASHRAE Journal - May 2014 - Cover2
ASHRAE Journal - May 2014 - 1
ASHRAE Journal - May 2014 - 2
ASHRAE Journal - May 2014 - Contents
ASHRAE Journal - May 2014 - 4
ASHRAE Journal - May 2014 - 5
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ASHRAE Journal - May 2014 - Cover3
ASHRAE Journal - May 2014 - Cover4
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