Keeping Cool in Mexico City

With average temperatures nearing 80 F year-round, Mexico City would not be an obvious candidate for a glass-clad shopping center.

In fact, when the plans came in for Magnocentro26, a 246,000-sq.-ft. shopping and entertainment center located in a high-income area of Mexico City, there was some concern that the four-level glass atrium and generous skylighting specified for the project would result in significant solar overheating that would drive up the cost of keeping the center cool. But the architects of Magnocentro26, which is owned by a joint-venture partnership of New Hyde Park, N.Y.-based Kimco Realty Corp. and Mexico City-based Frisa, came up with an ideal solution: a high-performance glazing product, from Palo Alto, Calif.-based Southwall Technologies.

The product, XIR/Emerald Blue laminated glass, is designed to reduce unwanted effects of heat and light from the sun. It allows for the extensive use of glass and benefits from natural light while reflecting unwanted solar energy. Some 35,000 sq. ft. of the flat tempered XIR glass were used in the Mexican shopping center.

“XIR blocks nearly 100% of the sun’s damaging ultra-violet radiation and a significant portion of unwanted solar heat,” said John Miller, spokesman, Southwall Technologies.

The laminated XIR product is a transparent film that is encapsulated between two layers of polyvinyl butyral (PVB) and glass to form a protective barrier against the harmful effects of the sun. The finished product has a unique, lowreflectance appearance. Unlike other approaches that absorb and re-radiate heat, XIR film’s spectrally selective metallic coating actually reflects destructive infrared and UV rays without impairing visible light transmission, according to Miller.

In applications such as that of Magnocentro26, XIR has a low-reflectance appearance, Miller said, allowing greater than 70% visible light transmittance while reflecting about 50% of the invisible heat.

Glazed monolithically or combined into sealed insulating glass units, XIR film can be laminated with annealed, heat-strengthened or tempered clear glass, or combined with tinted PVB and tinted glass.

“One thing that made the installation so perfect for Magnocentro26 is that XIR for laminated architectural glass is particularly effective for bent-glass constructions that also require solar control,” Miller said.

According to Miller, it is difficult to bend direct-coated glass. But XIR is effective for achieving both curvature and high solar control.

While no energy savings have been calculated because of the newness of the center, Miller said that he is confident savings will be realized.

“The center was able to use dramatic amounts of glass while reducing the temperature range so that normal temperatures could be maintained through moderate use of air conditioning,” he said. “What the mall owners wanted to avoid was a situation where inside temperatures were so high that an inordinate amount of air conditioning had to be used.”