Greenfields Community Housing Head Office

The brief from Greenfields Community Housing was for a flexible head office that demonstrated and embodied the organisation’s commitment to the environment. Richards Partington Architects responded with a design that efficiently combines passive and active features, creating a comfortable, low energy building that achieved a BREEAM rating of ‘Very Good’ and also received a Certificate of Excellence at the 2010 Concrete Society Awards.

The building incorporates a special ‘community space’ for residents and local groups to hold meetings and activities free of charge. It has good accessibility and transport links for its 10,000+ residents and has brought a cutting-edge, environmentally-friendly building to the Braintree District.

The three storey building’s in-situ concrete frame forms an integral part of both its passive and structural design. Exposed concrete soffits provide a high level of thermal mass for fabric energy storage, enabling radiant cooling during the summer and the ability to absorb and re-radiate some of the internal heat gains during the heating season.

The layout is designed to achieve good cross ventilation via high level windows, with perforated panelling above the internal glazed partitions to ensure air flow is not impeded. In periods of hot weather, night time ventilation is used to cool the building fabric.

Mechanical ventilation is also available via a raised floor, allowing a mixed-mode approach that takes full advantage of natural ventilation during the summer months. The supply from the mechanical system can be preheated or cooled by a ground source heat pump linked to an underground network of pipes that absorb or reject heat to the surrounding soil.

To reduce the embodied CO₂ of the concrete a 50% ground granulated blast furnace slag (GGBS) concrete mix was used. Internal flexibility is helped by using a flat soffit within the 6m/7m x 6m structural grid. An interesting feature of the soffit is the regular array of a 25mm-deep, 1.2m-diameter circular recess which provides visual interest to the slab. The circular recesses were formed using plywood discs with chamfered edges fixed to the shuttering.

The discs, and in particular their edges, were sealed to avoid damage and to protect the end grain from absorbing water when the concrete was poured. Large circular pendant lights complement this feature, accentuating the subtle recesses. A consistent smooth finish was achieved by producing a series of trial panels and working closely with the concrete contractor