Underfloor Cooling Makes Headway in the U.S.

Tricky system in Hearst Building lobby atrium is a big success thanks to Daniel H. Nall

If anyone can persuade risk-averse developers and owners to be the first on the block to go with a rarely used or potentially problematical technology it is Daniel H. Nall, director of advanced technologies for Flack+Kurtz, New York City. The 150,000-sq-ft underfloor cooling system for the 1.7-million-cu-ft atrium lobby of Manhattan’s 15-month-old Hearst Building is a case in point. It’s the first underfloor cooling system in a lobby of a commercial U.S. high-rise and the first such cooling system in New York City.

Nadine M. / ENR Careful engineering resulted in an atrium lobby floor without puddles the pitfall of underfloor cooling.

The system consists of water circulating in tubing set into the topping slab. Architects like underfloor heating and cooling for large open spaces because there is no need for intrusive ductwork. Owners like the system because it frees up real estate otherwise taken by fan rooms and ductwork risers. Both like the system because it is more energy efficient than traditional air conditioning.

But there’s a hitch to underfloor cooling in humid climates. If it is not correctly engineered, condensation puddles can form, creating a slippery situation.

Nall’s floor has stayed bone dry through two cooling seasons “The design has proved to be totally successful,” says Tom Scarola, director of engineering for Tishman Speyer, New York City. The firm developed the Hearst project for Hearst Corp.

If it is difficult to innovate in the U.S.,  it is doubly difficult to innovate in New York City. “The great thing about Dan is that he is always willing and able to embrace new systems and seek to make them work in the New York context,” says Brandon Haw, senior partner with Foster+Partners, the architect for the 46-story building.

Multimedia  View Award of Excellence Luncheon and Acceptance Speech of Daniel H. Nall   April 3, 2008

Though Foster had used underfloor cooling in a couple of projects in Europe, the Hearst installation was its first in the U.S. “Things are changing rapidly in the U.S.,” says Haw. “It is people like Dan who have, over the years, had the foresight to see that the move toward greener and more efficient systems will slowly but surely take hold in North America and elsewhere in the world.”

Foster needed a partner willing to accept the technical challenges their design presented, says Scarola. There were many meetings and even peer reviews that challenged it, but “Hearst and Foster ultimately trusted Dan and F+K,” he says.

Scarola says if Tishman Speyer has occasion to use underfloor cooling again, there will be far less apprehension than there was with the Hearst job, thanks to Nall. “What we will not do is trust very many other engineers to design the mechanical system to handle it,” he says.

Nall, registered as both an engineer and an architect, has been honing his innovation skills and management techniques for 10 years at F+K. He maintains it is imperative to be “very conservative” about the physics during analysis and to use the very best analytical tools, including computer simulation and mock-ups. It also is critical to be meticulous about details and innovate a little bit at a time, and it is necessary to keep an eye on construction.

For Nall, who is working on another underfloor cooling installation, thermally active floors are just one slice of the innovation pie. “Dan is our nutty professor, so whether it is curtain walls or the more advanced engineering systems, such as radiant cooling, displacement ventilation, solar and wind energy, geothermal systems or advanced control algorithms, Dan can be found passionately...promoting...new technologies,” says David Cooper, F+K’s executive vice president.