As the housing market cools down in many areas, rental housing is heating up, with rents rising and the amount of available rental housing dropping, experts say.

“Demand is increasing for apartments because people say house prices are too high, and with interest rates going up, the affordability of home buying is less achievable,” said Rachel Drew, a research analyst with the Joint Center for Housing Studies at Harvard University.

“This increases the demand for rentals,” Drew said. “Because rental production has been low and replacement of existing units is not good, the supply is not expanding. So higher demand raises the price rather than increasing the supply.”

As market fundamentals are changing, a new wave of apartment listings services has stormed the Web, among them Apartments.com, Rent.com and MyNewPlace.