The U.S. apartment vacancy rate increased in the second quarter and rents were higher, according to a report from Reis Inc.

The national vacancy rate rose slightly to 4.4 percent in the second quarter from 4.3 percent in the first quarter, the real estate research firm said.

Asking rent rose 1.3 percent and effective rent grew 1.1 percent in the most recent quarter. They increased 3.5 percent and 3 percent respectively year-over-year, according to the report.

"Total inventory is expected to increase significantly in 2017, however, construction in the second quarter was lower than expected in a quarter that tends to see the highest activity," the company said.

New construction totaled 36,477 units in the quarter, down from 57,586 units added a year earlier.

This was the lowest quarterly addition in more than two years, the report added.