"Demand is ridiculously high," said Jackie Yong, a 17-year employee of J. Freeman, Inc., a plastics distributor and sign supplier in Boston whose products include plexiglass and other plastic sheets.

By reflecting, on average, 96% of infrared and visible light, the porous PMMA sheets cooled down the sunny 80 degree Fahrenheit outdoor air temperature to 65.3 degrees Fahrenheit inside the box.