A consultant hired by the county had found that the glare from architect Frank Gehry's swooping steel building, which opened in 2003, raised the temperature on the sidewalk to 140 degrees.
Most of the $274 million building is covered in dull brushed steel, but certain sections were brightly polished. Those sections of the hall, which total about 4,200 square feet, also magnify light because of the angle of their curves.
Gehry has agreed to the changes, which will be completed later this year.
"It's about time," Sheila Nixon, who frequently walks past the hall, told the Times. "We feel like ants under a magnifying glass."