The 1.2 million-square-foot Westbrook Corporate Center in Westchester, Ill., needed a few fixes.

The complex, made up of five 10-story multiple-wing buildings, was in need of lighting and HVAC system improvements, had lower-than-average occupancy and high energy costs. Other problems included poor visibility in conference rooms and outdated infrastructure.

Owners Arden Realty Inc. started by replacing the lighting with LED fixtures from General Electric. They offer brighter lights and lower energy consumption, and are expected to last up to 15 years, officials said.

“The updated lighting is actually more evenly distributed and provides dimming capabilities to fit the needs of a meeting while also allowing meeting participants to see more clearly with a natural light color,” said Craig Hall, a GE manager. “We’re also pleased that the new lighting saves time and money from a maintenance standpoint.”

The HVAC system was also upgraded. The complex was previously known for having hot and cold spots. To avoid disturbing the complex’s 40 tenants, the air-handling system was removed starting at 6 p.m. on a Friday and the installation of the new unit was completed by 6 a.m. the next Monday.

It now uses 30 air-cooled chillers -— two in each of the 15 wings. Each wing has a backup chiller to ensure uninterrupted operation.

The upgrades worked. Tenant temperature complaints dropped, according to Fred Lowy, the complex’s chief engineer.

“This past summer, after the first improvements were completed, our tenants let us know that they were comfortable all day,” he said. “Previously, we depended on an outdated ice storage system on the roof that would lose the ability to cool the buildings mid-day. The size and capacity of the ice storage system weren’t able to meet demand. Tenants would start to feel warm and uncomfortable throughout the afternoon hours.”

Controlling the components are Trane Tracer SC controls, which monitor the lighting and HVAC systems using the existing building-automation system.

It’s a combination that works well, said Sheree Worcester, senior property manager for Westbrook Corporate Center.

“We met with our largest tenant recently, and the first thing he said was that this past summer was the first time he didn’t need to put in a ’hot call’ complaint indicating tenants’ discomfort,” Worchester said. “This is pretty amazing because typically it’s impossible to satisfy 100 percent of your tenants with HVAC. That we were able to so completely satisfy our largest client is pretty impressive.”