Residential construction loans at Iowa banks posted double-digit gains in 2015 and helped boost loan growth 6.4 percent over 2014, according to the Iowa Bankers Association. By the end of the fourth quarter, banks had loaned $49.5 billion, with the largest increases in the categories of construction and land development, which would include loans for single-family residences and apartment buildings. Based on data from the Federal Deposit Insurance Corp., net loan charge-offs at Iowa banks dropped to 0.09 percent of total loans, compared with 0.16 percent the year prior. Noncurrent loans were down to 0.55 percent of total loans from 0.64 percent in 2014, while nonperforming loans declined to 0.48 percent from 0.61 percent. Other measures of banking performance also improved, with return on assets rising to 1.19 percent from 1.15 percent over the year. Bank profits were $914 million for the year, up 7.8 percent from $848 million in 2014. Iowa banks had total assets of $79.2 billion in 2015. Nationally, bank net income improved during the period to $163 billion from $152 billion.