The new science block in Belvedere College is a dynamic space designed to serve a number of uses, including an all-round education, writes Emma Cullinan

The Dublin schoolboys move from classroom to classroom on their morning break, swirling around each other in an innate choreography, creating the thermal energy generated by teenagers in crowds. From the canteen this heat is drawn up through the beautiful atrium of Belvedere's new science block - where natural ventilation counteracts it.

Yet it's the aesthetics - rather than the functionality - of the space that hits you first. Bleached beech battens in symmetrical sequence rise up the walls to the glass roof, creating an ordered ladder that makes your eyes climb upwards.

At the top of the wide beech and mahogany (from managed sources) stairs, the batten pattern is relieved by a walkway, and the overall composition is also balanced with glass fronted bays which protrude from the first and second floors. On the opposite wall, plain plaster provides a balance.

This attractive space derives from functional considerations: a requirement to naturally ventilate and light the area; a need to enclose balconies, walkways and stairs, to stop any falls during schoolboy "horseplay"; and the creation of multifunctional space that caters for pupils during the day and visitors to the school's theatre in the evening.

The beech slats allow for air movement as do the overlapping glass panels on the edge of the balconies.

The new Dargan-Maloney Science and Technology Building (named after the rector Fr Joe Dargan SJ and former headteacher Fr Leonard Maloney SJ), is the third phase of development at the Dublin boys' school, situated just off Parnell Square.

Architects Murray O'Laoire were taken on to develop a master plan for the site in 1996. "It's an essay in the concentration of space," says Sean O'Laoire, pointing out that most new schools are built on greenfield sites outside the city. Many former inner city schools also moved further out of the centre, but Belvedere has stayed. The theatre and science block are situated on a former car-park and playing field - the former has gone underground and the latter is on the roof.

The first phase of the development involved addressing health and safety, and fire issues, and the second phase saw the theatre development whose realisation was hastened by a donation from former pupil Tony O'Reilly after whom the hall is named.

The O'Reilly Theatre is a flexible space, with the architects having designed it to suit various occasions such as assemblies,parent/teacher meetings, school productions as well as use by outside bodies. It has become a core part of the Dublin Theatre Festival, says O'Laoire, who reckons it could be the largest proscenium arch theatre in the country.

The multi-use concept runs to the sports pitch on the roof of the building, which can be hired to outsiders: not least the architects themselves who play five-a-side football here once a week.

The theatre's foyer - with its tiled floor and board-marked concrete (bearing the imprint of the timber shuttering) brightened with white aggregate - is used as a through route by boys during the day. Near the front door is the reception desk, enclosed in timber, glass and white render, as is the theatre box office beside it.

Dual-purpose use has been catered for in the ribbed concrete refectory ceiling in which fluorescent lighting is hidden beneath mesh screens - for use during the day.

In the evening, when the school canteen is transformed into a theatre café, downlights in the ceiling are used instead. The hanging pendant lights - designed by the architects and made by Kent Stainless Technologies in Wexford - combine downlights for school hours and upright "candles" for dusky theatrical moments.

The notion of multi-use spaces has extended to the classrooms. In the science room the lab benches - with their bright yellow and green taps playfully conjuring up 1970s' Scandinavian fittings and with drawers from the Bulthaup school of design - are on one side of the room and the lecture area, with stepped seating, is on the other side.

The biology room is next to a greenhouse on the roof, to nurture a rounded education in the life of plants, and the renewable-energy workstation has equipment that is run by a solar panel and wind turbine on the roof which can be seen by students, up through the glass ceiling, as they learn about a greener world.

The entrance to the new part of the school is through large granite-framed double doors that serve as the main entrance for the whole school.

The Wicklow granite, used throughout the building, is favoured by project architect Stephen O'Driscoll for its warm yellow hue "which works better than the very white Chinese granite". The huge doorway clearly marks the entrance to the mix of buildings fronting Denmark Street. This includes Belvedere House built in 1775 (possibly to a design by Richard Cassels) at one end, a 20th century neo-Georgian building in the middle, and the new building at the other end.

This, in contrast with the contemporary interior, has been designed to be "quiet in its expression".

The facade addresses the rest of the street, with its variety of brick colours. The new building's redbrick seems carefully chosen to fit this patchwork.

Elements of the elevation make reference to Georgian design, in the reducing heights of windows as they rise up the building. These conjure up the Georgian trick of having larger windows at the base and smaller ones at the top, giving a perception of height and making the most of natural light (with the small windows where there is most natural light and the taller windows down where things are dimmer). Although the building's overall horizontality slightly jars with the vertical rhythm of its Georgian neighbours.

Happily the facade, like the interior, steers away from a repressed, unrelieved flat plane. There's rustication at the base, in the form of channels in the brickwork; inset bay windows divided by chunky columns; and a slit window to the right of the entrance offering a sassy slice of a Georgian sash.

The front of the building sits harmoniously while the interior lifts the spirit. Warmth has been an important consideration, with that yellow hued granite along with the timber, which O'Driscoll aimed to install at all available opportunities throughout the building.

Cleverly cooled by natural light and cross ventilation the refectory space is a warm area, due to the materials, overall composition and those hungry teenagers.