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10 Years On: Evaluating kroll’s eco school

Ten years ago, the AR published a new secondary school at Caudry in northern France by Lucien Kroll, which marked an important advance in green building. The result of an architect/contractor competition, the school had to meet a demanding list of ecological criteria. As reported in January 2002 these were met and the school got off to a good start. But how has its life developed?

In 1992, the Green Party politician Marie-Christine Blandin, a former biology teacher, was elected President of the Regional Council for Nord Pas de Calais, and bargained for a special building programme, Haute Qualité Environmentale (HQE). A new Lycée (school for 15-18 year-olds)1 was required at Caudry, a small industrial town near Cambrai, former centre of the lace industry. This became a test vehicle, launched as an architect/contractor competition in 1996 with a strict agenda of 67 environmental performance targets and heavy financial penalties for non-compliance.

The HQE criteria naturally demanded minimal energy consumption, low embodied energy and short transport distances, but also much more. Toxic materials had to be avoided and every kind of recycling considered, even reuse of the building for a different purpose. Water consumption had to be minimised and excess rainfall retained, with daylight to be provided wherever possible. A ‘green site’ was expected, without disturbance, pollution or waste: even the contractor’s site-huts had to be redesigned.


The place from the other end, looking east towards the administration with the Arts tower on the left

The competition was won by Lucien Kroll’s office AUIA and contractor Caroni, along with technical specialist Alain Bornarel and engineer Sodeg. Although the competition process precluded the full participation that Kroll favours, he was able to study the town, and on winning the competition, to consult the school staff in detail before making adjustments. The school was built in two phases from 1997 to 2001 and has been in full operation for 10 years.

Today, only the solar chimney on the administration block, the solar protection on the south sides, an array of solar cells and a solar water heater directly signal the ecological theme. But there is more behind the scenes, including a mechanical ventilation system with heat exchangers, heat pumps and underground ‘Canadian wells’ (buried tubes to preheat or precool the air). Visible but less obviously ‘ecological’ is the exceptional daylighting, intended to reduce electricity consumption and to improve environmental quality, allowing pupils and staff to see out and register the time of day.

We have come a long way from the ‘schools without walls’ of the 1960s, with their deep plans and the blanket assumption that artificial light is superior because it is more controllable, and that windows are just a way of wasting heat. Daylight and view are now recognised as having a measurable psychological impact, but artificial light still sets the norm because of building regulations, and it is not unusual to see new British schools on sunny days with every fluorescent tube alight. One of Kroll’s main ambitions was to build a fully day-lit classroom, and he found that the necessary light level could only be achieved by introducing daylight from both sides: from external windows and via a fully top-lit central corridor.

ground_floor_01Ground-floor plan of the complex with the main entrance to the right, under the bridge formed by the administration

Not only here but throughout the school daylight floods in, sometimes from apical rooflights as in the library, sometimes with generous windows or through small courts. Meeting the energy criteria did not preclude the use of glass or enforce a minimum envelope: it was more a matter of thick insulation, of sealing junctions ‘fanatically’, and of avoiding cold bridges between the warm structure and the cold cladding.

Kroll long ago discarded a Brutalist concern for substance, so the exterior is all added facade. This had the advantage at least that Kroll and his team could ring the changes on the cladding to distinguish the various parts, using a skin of brick here, timber boarding there, even a coat of stainless steel on the administration − the worst for embodied energy but of limited area and balanced by abundant use elsewhere of larch shingles, the least energy-hungry cladding of all.

A chance to stake out varied territoriesArticulation of parts within a complex remains for Kroll a fundamental issue. Adding such a large institution to a small town in one lump would have caused problems of scale and contrast, while building to a repetitive mechanical system would have produced an oppressive sameness to endure throughout its life. It was therefore desirable to differentiate the space, making a science classroom different from a language room, or a library from an assembly hall.

As Kroll argued long ago, this is less a question of functional convenience or efficiency than of forming recognisable territories: the making of places with which to identify, to feel at home, and by which to navigate. He thinks we need to put back artificially some of the variety and complexity that used to arise spontaneously when buildings were added one by one in response to changing conditions, before the advent of reductive planning briefs and the dominance of technically driven assembly.

At its heart, the Caudry school has une place, like a French village or town square, across which the two main ranges of teaching buildings face one another. Ordinary classrooms are on the north side, technical ones to the south, reflecting the more or less 50/50 division between academic and vocational teaching. The place is an outdoor room that can be used for social events and celebrations, but it serves predominantly on warm days for the pupils’ breaks. Regularly placed trees add summer shade, and benches around the edge, many beneath glass roofs, produce extended thresholds.


The polygonal school library with its apical skylight and generous windows beyond. The roof structure is composed of glulam beams with a minimal use of steel for the ties. Artificial light is switched off because daylight suffices

The east side of the place is dominated by the metal-clad administration block, forming a bridge over the main gate at ground level, which is opened when pupils arrive and leave.8 Next to this, the north-east corner holds the library and meeting hall, the south-east the pupils’ common room, both helping to contain the entrance.

To the west, at the other end of the place, the technical teaching block folds around to enclose the south-west corner, whereas to the north-west is the polygonal Arts tower, the highest part culminating in a music room like a small concert hall.The inviting set of steps at its foot in the north-west corner of the place leads up towards the dining hall and kitchens beyond.

This change of level is a reminder not only that site contours are respected and retained, but that foundation spoil has been absorbed into the landscape, precluding the energy costs of removal and dumping. In the south-east and lowest corner of the site is the pond designed to retain the run-off after heavy rain, delaying it before it passes on through to the town’s river system.

The final element in Kroll’s bird’s eye view is a row of dwellings on the south side provided for school personnel. This extends a pre-existing street of old industrial cottages, integrating the whole complex into the town. The street’s given angle is the main reason why everything is skewed slightly west of the south.

First impressions were encouraging: the school appeared in good condition with a patina of weathering but no evident graffiti or vandalism. Classrooms and corridors within were also well maintained with almost no accidental damage and little evidence of age. The ubiquitous linoleum, almost alone on the list of flooring materials after embodied energy and recycling load implications had eliminated the rest, looks remarkably good. It is rewaxed once a year and polished regularly: the few points of damage were at external thresholds due to driving rain or where minor movement had occurred.

Light and landscape

For a dullish January day, the quality of daylight seemed exceptional nearly everywhere, with frequent and varied views to allow easy orientation. The external greenery is still attractive, especially the sedum roofs which remain colourful even in winter, and the rain-holding pond with its rushes and water plants among which lurk a few moorhens. It was the worst time of year to see the plane trees in the place or the fruit trees near the restaurant, to register the difference between mown lawn and the rougher areas of meadow cut just twice a year, but the landscape is evidently conceived as a garden, well tended and lacking expanses of loveless tarmac.

Some coloured tarmac is reserved for the central place where the patter of feet is greatest. The head, who has been present at the school from the beginning, confirmed that the low-energy performance has been sustained, and admitted that his initial fears about potential building failures − prompted by the complex shapes and varied materials − had proved unfounded. He claims the school has a happy atmosphere, which is evident from the way the pupils respect and care for the building, and while I was there the pupils seemed consistently relaxed and well-behaved.

The head offered lunch, and we ate the same excellent three-course meal as the pupils, sitting and chatting with teachers, concierge and kitchen staff, with an evident sense of equality. Longer-serving staff members take the school for granted and sometimes grumble about details: why have science labs on three levels then have to carry materials up and down in a lift? But those who have taught elsewhere are consistently impressed, and the head confesses he would hate to return to ‘an ordinary school: the concrete, the blind corridors’.


The Arts tower seen across the flourishing sedum-clad roofs
of the school restaurant

He is proud that the rain collection has proved so adequate for the grey-water system, drastically reducing dependency on the local water supply, but regrets it gives him no economic advantage on paper. Moreover, although the artificial lake has become a model biotope, the fully prescribed French national curriculum does not allow its educational exploitation. In a few places, teachers and pupils have added plants, but the role of the building in deliberate ecological education is not a strong theme.

The rigidity of the curriculum is felt in other ways, particularly the reduction of the beautiful music room to a store. As music is not a curriculum subject, it awaits the enthusiasm of a dedicated teacher prepared to work for free outside hours.

The head also has some grumbles. Neither the solar chimney on the administrative wing nor the Canadian wells precooling the air of the classroom blocks cope adequately with prolonged heatwaves, and the temperature of the upper classroom corridor, fully glazed for the sake of daylighting, can become excessive (the one in the second phase was given fixed shades to south).

When the school is closed for Christmas, it can take days to warm up due to the thermal flywheel effect. And while he appreciates the virtues of polygonal rooms for library and restaurant, the head criticised the use of non-rectangular spaces for working rooms such as kitchen and stores, showing me places where racks do not fit, though it may have been beyond the architects’ control.

A question of style

For pupils, staff and parents, the school’s appearance has long been accepted as normal and it fits easily into the town, but for architect-outsiders its style is controversial, offending rationalists and minimalists alike. So despite the building’s record-breaking eco-performance, only one French architectural journal published it, and then on the insistence of its editor against the protest of colleagues.

Kroll has always been anarchic, sceptical, even something of a Belgian surrealist in his humour, but he has argued his case articulately over a long period and deserves to be taken seriously. Part of the style problem is that the school is very difficult to photograph, since the important central place does not figure except from above, the flow of space is hard to catch, perspectives are distorted by the un-right angles, and more views are needed to show the school’s riches than can possibly be printed.

There is also the old problem of attention being drawn to details, which in real life seem of minor importance. Yet the architectural world has come to depend on photo-like images to the exclusion of all else, often re-cooked in Photoshop with the lighting and colour ‘improved’, and therefore even further removed from reality.


Restaurant, kitchens and service building, as seen from the top of the Arts tower

Traffic in images has displaced real experience, and the skill of reading plans and sections to reconstruct a place in your head, necessary in the days of more restrictive media, is becoming a lost art. Recorded images even dislodge individual memories of a place, for as you gaze at them, you reconstruct and replace your internal vision. After initial enthusiasm for the HQE, Kroll is disappointed.

Despite the achievement at Caudry, he and his team did not get another commission, and the intended follow-ups of the school’s performance were dropped for lack of interest. There have been HQE projects by others but the programme has been watered down, and it is easier to appear green with a few stuck-on solar panels and wind-turbines than to work through all criteria and their hidden impacts.

‘How can we tell what difference it makesto avoid toxic materials?’ asked the head. But for the outside world, the example of the Caudry school is a challenge, demonstrating what is possible and the kind of measures we should surely be taking for the sake of the planet. I am left with the impression of a friendly and successful school, generous in daylighting and views, excellent in its place-making, but essentially normal. Only on reflection did it occur to me that there are no real signs of strain and sacrifice in having to conform to a rigorous ecological agenda.

The original article on Lucien Kroll’s Eco School can be found in AR 2002 January (p. 67-73) or here


Dennis Gilbert

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