Abe and Irene Pollin. Family photo, courtesy of Irene Pollin. (COURTESY OF IRENE POLLIN)

The Irene apartment building in Chevy Chase, Md., is under contract to be sold to a real estate investment company for $215 million.

Irene Pollin, whose family owns the building, sent a letter to residents Monday informing them of her “mixed feelings’ about the decision to sell over the holidays, but said it was the right decision for the family.

The 500-unit building was one of the last residential buildings built by the late Abe Pollin, the former Washington Wizards owner, philanthropist and developer. He named the building for his wife, Irene, who keeps an office there.

Irene Pollin sent a letter to residents this week saying the sale of the large apartment building near the Friendship Heights Metro is “not yet finalized” but names the buyer as Equity Residential , a public real estate investment trust. A resident read the letter to a Washington Post reporter.

Equity Residential, which owns and manages apartment buildings across the country, has several other buildings in the Washington, D.C. area. A spokesman for the company confirmed the sale agreement and the purchase price.

Pollin goes on to say in the letter to tenants that, “The main and only reason we are selling is that my children are involved with other businesses and professions. This is the correct thing to do for our family.”

Last summer, she sold several other real estate properties. The Reliable Source reported in June 2010 that she sold her Middleburg estate (five bedrooms, five baths, indoor pool in horse country), her Rehoboth beach house and Verizon Center in one week.

One resident said he was concerned the building might be converted to condos but Equity Residential spokesman said the company has no such plans. “We own and manage apartment buildings — that is what we do,” said Equity Residential spokesman Marty McKenna. “It’s well located, a high-quality asset in a great location.”

The Irene features a rooftop tennis court and two swimming pools and other amenities. Pollin, in her letter, says she will keep her office in the building after the sale.

The Irene’s Web site says, “The prestigious Smithsonian Institution’s Best Address publication once referred to The Irene as ‘an enviable address.’ That description is still well deserved today.”