Kingspan says acquisition of Warrington-based firm will complement its existing panel businesses.
Kingspan has acquired Advanced Thermal Composites composite sandwich panel manufacture for £20m.
ATC manufactures panels for the cold storage and food preparation sector. Kingspan says ATC complements its existing businesses in the UK.
Kingspan will pay a further £1m over the next three years depending on the value of ATC's net assets.
ATC had a profit before tax of £3.3m and turnover of £15.3m for the year ended 31 August 2004. It is expected to have net assets of £3.6m excluding cash.