Housing construction rose a moderate 2.4 percent in July, the government reports, but economists warn that rising mortgage rates could make the two-month housing rebound a brief one. The Commerce Department said Wednesday that new homes and apartments were built at a seasonally adjusted annual rate of 1.49 million units last month after advancing 4.4 percent in June. Housing starts dropped a sharp 12.1 percent in May to the slowest pace in three years, and rising mortgage rates were blamed.