Its £79m project at Guys Marsh prison will deliver two houseblocks, one with 122 cells, the other with 59, to increase capacity by 31%.

The project includes a new extension and a general refurbishment programme.

Designed to be net zero carbon in operation and achieve a BREEAM Excellent environmental performance rating, the new house blocks feature air source heat pumps and LED lighting.

ISG is also building on its six-year partnership with HMP Liverpool, where the contractor has worked to modernise and upgrade accommodation at the prison, parts of which date back to the mid-nineteenth century.

Its latest £56m scheme sees a full overhaul to support the prison’s proposed change in status from a Cat B to a Cat C facility.  

The comprehensive programme includes site-wide electrical infrastructure upgrades, supplemented by new boilers, the restoration of all wings, and the addition of a new workshop.

Alistair McNeil, ISG’s sector director, said: “Our projects at HMP Guys Marsh and HMP Liverpool not only address a need for prison places but will also support government carbon reduction targets, delivering buildings that cost less to run and maintain in the future.”  

ISG was recently appointed to the MoJ’s five-year, £2.5bn constructor services framework and is currently working on the upgrade of HMP Birmingham.

ISG is also one of four project partners on the MoJ’s £1bn New Prisons Programme alliance.