"Clear and Cool," Feature Article, January 2006

clear and cool

Retrofitting a stadium with new escalators led to using a novel material.

by Jeffrey Winters, Associate Editor

there's an old saying that you can't do only one thing. For the operators of the Amsterdam Arena in the Netherlands, the thing they wanted to do was add an escalator system to help speed spectators from the parking garage to the seating area. Before they were through, however, they wound up being the first users of a new heat-repellent material.

The Amsterdam Arena is unusual among European stadiums, many of which date back to the early part of the last century. Completed in 1996, it has much in common with recent American football stadiums, most notably a sliding transparent roof that enables players and fans to escape the clammy Dutch winter weather.

"The stadium was really the first multifunctional stadium in Europe," said Sander van Stiphout, project leader with the Amsterdam Arena, "and we've tried to maintain our state-of-the-art image."

No greenhouse effect: Clear Lexan panels enclosing this stadium elevator trap 40 percent less heat than normal transparent coverings.

Ajax, the famed Dutch soccer club that plays its home matches in the Arena, is just one draw among many. Over the course of a typical year, the Arena will hold more than 70 events—everything from international soccer tournaments and American football games to pop concerts and dance parties.

One American-style aspect is the stadium's nod to the automobile: The 51,859-seat stadium sits atop a 2,000-space parking garage. (The configuration is similar to Cincinnati's former Riverfront Stadium.) Placing the stadium bowl above the transportation infrastructure cut down on acreage in land-scarce Amsterdam. But it came at a price—a long climb for spectators. After fielding complaints about this, the owners decided to build an escalator system to whisk people the nine stories from ground level to the seating area.

"We don't have that much space inside the stadium structure," van Stiphout said. "That meant that the escalators had to be placed on the outside of the stadium structure."

Open-air escalators have their drawbacks. Maintenance is more difficult, to be sure, especially in a damp climate like the Netherlands. And many riders experience unpleasant vertigo unless the escalator is at least partly enclosed.

The architects involved in designing the new escalators wanted something airy and modern—a translucent or even transparent enclosure. But glass and clear plastic materials have the unfortunate property of trapping heat, creating the possibility of the escalators becoming more unpleasant on a summer's day than the walk up from the parking lot.

But this is just the problem that researchers at GE Plastics had been working on. "The objective is to admit as much light as possible while excluding infrared radiation," said Lennard Markestein, marketing manager for GE's specialty film and sheet division in Europe. One popular solution to this problem is printing a perforated reflective screen over clear plastic or glass, but while this cuts down on heating, it blocks much of the potential incoming light.

As a result, GE had developed the Lexan Solar Control IR sheet, which was designed to cut down substantially on heating from sunlight. The material is composed of clear Lexan, a polycarbonate thermoplastic commonly used in such high-performance applications as fighter jet canopies. It is embedded with nanoscale particles that absorb incoming infrared.

In testing done at a GE technology center in Bangalore, India, the Lexan panels cut down heating by 40 percent over other clear glazing and admitted some 40 percent more light than comparable heat-reflecting coatings. The panels hadn't yet been used in a real-world application. Even so, the material looked promising, so the architects went ahead with an escalator design incorporating the panels.

Two of the four planned escalators were constructed this summer and put into operation, and the other two were completed in the fall. Thus far, the escalators and their enclosure have been a success—not too claustrophobic, not too exposed, not too hot.

"The stairs are still in place, so you can climb them if you want," van Stiphout said. "So far, nobody does."