Accessory dwelling units (ADU) go by a variety of names — in-law suites, garage apartments, granny flats — but the concept of a smaller, self-contained living unit on an existing property is becoming more popular, particularly in high-cost areas of the country, according to a new study by Freddie Mac.

Freddie Mac identified 1.4 million ADUs in the country, more than half of which are in California, Florida, Texas and Georgia. But the Chicago metro area, with 13.7 percent year-over-year average growth, did make the list of top 25 metropolitan areas with the fastest growth in ADUs entering the MLS market for the first time.