The architects behind the US$20m (€17.7m, £13.8m) renovation of the Westmoreland Museum of American Art in Greensburg, Pennsylvania, have claimed their work has launched “a new era” for the institution.

New York studio Ennead Architects have used a simple palette of materials and textures – including precast concrete, zinc, brick and glass – to unify the 13,500sq ft (1,250sq m) expansion with the existing neo-Georgian structure.

A new eastern brick wing mirrors the existing west wing to secure the symmetry of the building, while supporting a new zinc-clad cantilevered gallery which extends southwards.

Perpendicular to the new wing is a new south façade that visually frames the original brick building with a two-story colonnade.

The expanded facilities include a huge glass staircase linking the new and existing galleries, a studio for children’s cultural programmes, a multi-purpose space for concerts, a museum shop and an informal café.

“We were inspired by the museum’s conviction that design had the power to fulfil their aspirations for the future – both for the institution and the building,” said Ennead design partner Susan T. Rodriguez. “We found their vision, collections and the site to be a compelling context for creating architecture that could strengthen and renew the identity and experience of the Westmoreland.”

In addition to the extensions to the building, a new landscape and sculpture garden by LaQuatra Bonci Associates has been added to create a stronger bond between the museum and the Greensburg community.

“It had always been our aim to create a building that enhances the museum’s position as a 21st-century beacon for the arts – both in the local community and as a revived cultural icon for the region at large,” said Ennead partner Timothy Hartung. “Having grown up in the area, it is also a personal honour to return and to be part of the Westmoreland’s future.”

Ennead Architects have previously renovated the New York Hall of Science. They are currently working on the Cape Horn Sub-Antarctic Centre in Chile and the hotly-anticipated Shanghai Planetarium.