A green-roofed underground office space in a sensitive location.

Invisible from the surrounding open countryside.

An exacting brief to provide 4000 square feet of additional office accommodation to an existing array of barn conversions in the very rural setting of Chilton would normally be a planning taboo.

However, the innovative nature of the proposal and lateral thinking used to justify the approach, was approved against the Planning Officer's recommendation.

The reinforced, waterproof, curved concrete underground structure, with roof-lights and windows to the east, south and west, provides a light airy open-plan space, wrapped in grass, that blends successfully with the surrounding countryside.

The green roof assists the ecological balance of the area and facilitates the slow run-off of rainwater, preventing overloading of surface water drains during heavy rainfall.

The underground structure is protected from extremes of temperature and benefits from the 'thermal store' provided by the dense concrete shell, making it naturally cool in summer and warm in winter.

Internally, the barrel-vaulted roof, clad on the underside with open-jointed larch boarding and sound proofing quilt behind, prevents the 1000 sq ft open-plan space from being an echo chamber.

The project won an Aylesbury Vale District Council Design Award.

The underground office site during construction.