Radiant cooling is cheaper to install, operate than conventional A/C

Our thanks to hydronic engineer par excellence Robert Bean for bringing this to our attention. An engineering paper on the offices of an Indian IT company demonstrates that radiant cooling is cheaper to install and operate than conventional HVAC. The large office building has two symmetrical halves, one cooled conventionally and one cooled by radiant.

Infosys Ltd. built the 258,000-sq.ft. building in Hyderabad. The company's engineer, Guruprakash Sastry, senior manager, green initiatives, for Infosys in Bangalore, noted in his report that the concept of building the structure in symetrical halves, one-half cooled conventionally and one-half cooled with radiant, was met with considerable resistance by consultants who said that radiant cooling would not work in India.

The conventional VAV side isn't minimal. It was designed to beat the ASHRAE Standard 90.1 baseline by 30%. Sastry writes in his report:

The most significant feature of the building is that it is split into two symmetric halves. One half is cooled by conventional (but very efficient) air conditioning and the other half by radiant cooling. All parameters in the two halves — area, number of occupants, orientation, envelope and lighting — are similar and therefore the building is ideally suited for comparing two different technologies. To start with, the building has a highly efficient envelope with perfect orientation, double walls with insulation, insulated roof and efficient windows with appropriate shading to maximize natural light in the building and minimize heat ingress.

As it turns out, the radiant side cost a little bit less to install that the conventional HVAC side. Better yet, after a year in operation, the radiant side is using 33% less energy.