Flat glass prices jumped another 0.9 percent in August after increasing by the same amount in July, according to the latest Producer Price Index (PPI) report issued by the U.S. Labor Department.

According to the report, flat glass prices are up 4.8 percent from August of last year and 4.6 percent over the last three months, thanks to a 2.8-percent spike from May to June.

The PPI program measures the average change over time in the selling prices received by domestic producers for their output, according to the U.S. Bureau of Labor Statistics (BLS). The prices included in the PPI are from the first commercial transaction for many products and some services.

The flat glass index sits at 127.7.

In another report, import prices for glass and glassware remained stagnant for the third straight month. Prices in that category are up 0.2 percent from August 2014, with an index of 129.7.

Export prices for glass and glassware, meanwhile also stayed put in August after a slight 0.1-percent decrease in July. Those prices are up 0.3 percent from this time last year and have an index of 98.9.

Prices of construction materials are down 0.4 percent in August following an increase of 0.3 percent in July. Prices in that category are down 0.7 percent from August 2014. Final demand for construction saw a 0.1-percent dip in August, but those prices are up 1.8 percent over the year.

On the whole, the PPI for final demand was unchanged in August, seasonally adjusted, following a 0.2-percent rise in July. On an unadjusted basis, the index for final demand decreased 0.8 percent for the 12 months ended in August—its seventh straight year-over-year decline.

Overall prices for U.S. imports dropped 1.8 percent in August after a 0.9-percent dip the previous month. Export prices fell 1.4 percent in August after declining 0.4 percent in July.