Sales to third parties for the second quarter of 2018 increased by $13.0 m to $99.8 m, from $86.8 m in the same period in 2017.
NCI said this was because of commercial discipline, emphasising project profitability over volume in a period of increasing input costs.
It added that volumes increased because of strong demand for cold storage products.
However, while sales were up, operating income fell to $1.5 m in the 2018 quarter. This compares with $19.4 m in the 2017 period.
The 92.1% fall in operating profit was a result of exceptional circumstances in both the 2017 and 2018 quarters. The company added that in the 2017 quarter, it sold an unusually high number of architectural panels.
The second 2018 quarter includes a $6.7 m loss following the sale of a Chinese factory.
The 2017 quarter operating income includes an insurance settlement. This was worth $9.2 m. It covered fire damage at a plant.
Across the company as a whole, sales were $878m in the first half of 2018. This is up 8% on $812 m in the comparable half of 2017. Net income flipped from a profit of $19 m in the first half of 2017 to a loss of $453,000 in the first half of 2018.
CEO Donald Riley said he was 'pleased with the strong second quarter performance'.