Rationalist representation.

Grafted on to an existing building, this new complex of offices for an insurance company is an expressively reductivist manipulation of space, light, materials and programme.

Wiel Arets is known for his large perspectives - Constructivist representations of an architecture formed by layers of concrete, steel and glass. Now these rationalist and deeply spatial visions are being systematically realised in a series of housing and institutional projects across the Netherlands. The AZL headquarters in Arets' hometown of Heerlen develops themes present in the Maastricht Academy of Arts (AR September 1995), creating a dynamic but tangible world in which design serves to animate the greater social organism.

His client AZL originated with the indigenous coal industry, surviving post-war pit closures to reform as a high-tech insurance and pension firm. Head office is in the inner suburbs of Heerlen, occupying a flat slice through a block framed by dense row houses. An existing building dating from the 1940s has had its innards modernised. A programmatically similar but expressively contemporary structure has been erected behind, parallel to the ersatz manor, and the two wings are connected by a bridging piece for reception, conference rooms and cafe. It is this spanning box which most dramatically defines the AZL image, its Gestalt.

Whereas the Academy in Maastricht has a more or less orthogonal relationship with its context - it is typologically autonomous and interacts through the medium of its glass block skin - AZL in Heerlen is grafted into its setting by Arets' manipulation of the ground plane and by his cropped, elongated views. A thin strip of the property - the only zone to stretch continuously to both perimeter roads - has been excavated and bermed to re-form the site as a folded base. This ramping becomes a concrete ha-ha, a flat channel in which employees' cars are parked progressively out of sight. It then wraps underneath the reception, making the entrance bar a literal bridge, to slope up between the office wings as a planted court.

The visitor sweeps in past the older baronial facade, now merely a skin, to encounter the reception structure projecting forward. Here it is a cantilevered snout with one horizontal window slot. Below, a thin raw ramp springs from its glass block floor (there are archives in the basement) to crank back against the soffit. As you turn to ascend a broad flight of steps into the glazed lobby, the surrounding houses with their returns and backyards disappear from view. The reception looks back at a somewhat secretive meeting room, laterally into the gap between the two office wings, and ahead into the double-height cafe.

This linear piano nobile is a kind of telescopic instrument with intermediary or sequential frames. It is striated longitudinally into a central zone of primary volumes - the structural bridge - with outer circulatory pocket of ramps and stairs leading down to the main conference room (suspended as a black steel box from the undercroft) and up to the managerial suites. While the final prismatic cage of the cafe enjoys a large oak spreading from a neighbour's yard, reception and the 200 or so office workers look out on to the central ramp gridded with changeable pots of always identical plants - a surreal parterre.

The two wings are approached via transparent slots - vertical zips with peripheral glimpses outside - and a technical area of washroom, open stairwell and elementally customised elevator. Work floors are basic, with grey-green carpeting, moveable translucent partitions and storage units which provide acoustic absorption. There is no mechanical air conditioning, but south-facing walls have a specially devised skin of stainless steel. Its horizontally perforated panels have electronically operated hydraulic jacks and hang 160 mm in front of a wall with sliding steel frames. This elegant double membrane has resulted in an unexpected 20 per cent saving on energy use, an example of Arets' deductive tactics producing a smart, beneficial solution.

Indeed the total project exhibits an economic logic in it details and fixtures. By and large, the interior is completed with modified systems. Arets stresses that AZL - even if its ceremonial spaces boast Eames and Starck furniture - is 'a really cheap building' with 'a normal developer's budget'. The concrete does not have the finesse of Tadao Ando - it is comparatively crude. Windows are punched through on an independent grid. There is an attractive moment in the stairwells where the interstitial concrete is eroded to house compact black radiators. The reception desks and conference tables of black birch and steel were designed by Arets' firm, but in a manner subsidiary to the space they inhabit.

There is a blackness throughout, particularly of metal components, which recalls the Dessau Bauhaus. (There are also foisted flattened hemispherical light fittings by Bauhausler Wilhelm Wagenfeld). AZL reminds us that architects can create new communal mechanisms without pastiche, without condescension. To move through this generously-scaled apparatus is to experience an extraordinary series of perspectives, achieved in a normal location and with an everyday programme. Unlike early functionalists, with their concern for plan, Arets interpenetrates the stratified floor volumes. To do this, he must fundamentally question the ground as tabula rasa. There is something in that which is both planetary, yet very Dutch.