Sales of apartment and condominium buildings in the Washington area surged to $4.7 billion in 2011, a $1.1 billion increase from 2010 and a sign that investors’ efforts to buy into D.C.’s heavy demand for rentals in particular is on the rise, according to CBRE Group Inc.

Multifamily sales for the year rose from $3.54 billion in 2010, according to CBRE. The brokerage’s District-based Multi-Housing Investment Properties team reported its own sales volume increased to $1.8 billion, up from $1.4 billion in 2010. Properties near Metro stations tended to command the strongest sale prices, and rental rates increased more in the District than in its outlying suburbs.