When Glaxo Wellcome briefed rmjm on designing a headquarters for its newly merged company, at Greenford, West London, it could have been a recipe for disaster in terms of environmental performance. The client insisted on maximising a sense of openness and transparency, both to reflect the intended working styles and to give out signals about openness and communication. Evidently this called for a maximised use of glazing, but the shape and orientation of the site meant that there would be long east and west facades, offering the prospect of nightmare amounts of solar gain.
rmjm has tackled this problem by completely glazing these facades, but also by creating a thermal flue which cools the facade in summer and keeps it warm in winter. This comprises an inner skin of glass (entirely sealed because the building is air-conditioned), with a second skin set 1m beyond it. In summer, air is let in at the bottom of the cavity and out at the top, through motorised dampers, ventilating the cavity. This has the effect of keeping temperatures down and reducing loads on the air-conditioning system, as heat that builds up in the flue is taken away by the stack effect before it can penetrate the inner layer of double glazing. In winter, the dampers are kept closed, trapping solar gain, so that the cavity acts as a warm blanket, insulating the building from heat loss. This reduces the U value, and the heating load.
The problems of glare are dealt with in two ways. There are large wooden louvres within the cavity, above eye-level for each floor, which provide shading from high-level summer sun without impairing views out from the building. Low-level winter sun is dealt with by automatic blinds inside the inner glazing.
Designed to accommodate approximately 200 staff and directors, the building has three main office floors, with a sloping site allowing the creation of a lower-ground floor containing exhibition space and a cafeteria set around the central atrium. The building is concrete framed, with structural bays of 7.2 and 6m, geared to a space-planning grid and component module of 1.2m. Service cores are at the northern and southern ends, which are clad with terracotta panels.
Construction cost, excluding furniture, was £17, 840,000. The total gross internal area, including the thermal flue is 8350m2; excluding the flue it is 7985m2, and this is probably a more reasonable basis for calculation, giving a cost of £2,234/m2.
The building won the 'Out of Town Workplace Building' category of last year's British Council for Offices awards, with a citation saying, 'This is a world hq. The jury applaud it for creating value.'
See construction study, aj 12.6.97