OAKLAND (KTVU) -- 2 Investigates has discovered that at least a dozen customers of a local window company who purchased high-efficiency windows "didn’t get what they paid for," according to a former employee.

KTVU obtained contracts from at least a dozen customers all across the Bay Area who purchased Low E3 glass from Anamar Window and contractor Clear Vision Windows, based in Hayward. But former employee Mark Torres claims that many customers didn’t actually get Low E3 glass for their homes, but instead were given a lower, cheaper grade of glass -- without their knowledge.

Low E3 refers to three layers of thin, transparent silver coatings on the glass that help radiate energy and improve the windows’ insulating properties, according to the manufacturer.

2 Investigates put the glass to the test with the help of Keith Perry, a San Jose State Professor and owner of a local, BBB-accredited window company called The Window Specialist. Perry used a professional device that scans the glass to measure how many layers of silver were applied, and determine whether customers were given Low E3 or Low E2.

At 12 of the 13 homes 2 Investigates tested, customers had at least one window where Low E2 glass was unknowingly installed, despite their contracts specifying Low E3.

“It’s a big deal. It’s a big deal,” said Perry. “They have no clue.”

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If you have concerns about installing Low E3 windows in your home, give Window Specialist a call at (510) 923-1000.