'Our main goal was to create a sustainable public building, both environmentally and socially, for building visitors and employees alike,' say Norwegian architects Siv Helene Stangeland and Reinhard Kropf, about the startling, ribcage-like Library and Cultural Centre they have recently completed in Vennesla, in southern Norway.

The project kicked off in spring 2009, when the architects - partners of Stavanger architecture practice Helen & Hard - won the competition to design a community space that would combine a library, a café and public meeting spaces, also uniting them with an adjacent existing cinema and adult educational facility.

The architects worked closely with user groups and took into account the continuously changing role of the modern library for a design that would produce a quiet haven fit for reading but also a place for meeting and social activities.

Completed in the end of 2011, the building sits next to a main town square, which the interconnecting buildings overlook. On entering through the square and a common doorway, the library section opens up through a generous glass façade towards an inviting sheltered courtyard with seating and space for social interaction.

The building's main design feature, however, is the impressive ceiling. This is made of 27 prefabricated glulam (glued laminated timber) ribs, a structure that allows for optimal ventilation and light, at the same time transforming into furniture when reaching the ground level.

Interiors are detailed in timber, using oak parquetry for all floors and plywood veneer birch for fixed fittings. Untreated heartwood pine is used for the outer façade.

The construction - mostly of prefabricated timber elements - conforms to low energy standards; a single central geothermal heat pump keeps the interior warm, the timber used comes from renewable sources, while air is released through a rib 'add-on' at ground level, returning through the ribs at the ceiling.

The result is an efficient building with a strong identity that offers a public space fit for the 21st century.