Manchester sustainability company ENER-G is building a £2m annexe to its headquarters in Salford.

The 12,500 sq ft building, which is due to open in December, will double the size of ENER-G’s offices and boost manufacturing space by 25%.

ENER-G manufactures a range of appliances, including heat pumps, meters, and data solutions, and has a particular focus on combined heat and power systems and biogas generators. The group’s worldwide turnover for the last financial year was £125m, with 47% coming from export sales.