Building Design
Post design & construction strategies
Building envelope and orientation
Natural ventilation and summer cooling
Existing elements determined the placement of the new buildings, which are located between remnant bushland on the north eastern boundary and an oval to the south. The oval was upgraded for school sports, and the remnant bushland protected by not allowing services to pass through, in contrast to former practices which brought services through thus contributing to bushland degradation.
The site fall from south to north was utilised to create the school on three levels corresponding to distinct functional zones: the senior school, the middle school and a transitional shared zone.
The buildings are laid out on east-west axes, linked by colonnades and covered walkways with courtyards and soft landscaped areas inter-dispersed.
The highest part of the site comprises main entry and administration, a courtyard with Upper School classrooms to the right and Arts / Technology Area and Gymnasium to the left. At the end of the courtyard, steps lead down to Cafeteria, Library and promenade areas that form a link to the Middle School which is on the lowest level. The Middle School is symmetrically arranged into four spaces, each with their own facilities, to serve four 'learning communities'; there is a common outdoor area ('student forum') at the mid intersection point.
Buildings are either one or two storey, steel framed with cavity blockwork and and steel roofing. The blocks are reconstituted limestone, chosen for consistency with local building traditions. Cavity brick construction is also an established tradition in Western Australia, with most new estate housing being double brick, unlike the eastern states where brick veneer is more common. With the limestone blockwork and colonnades the building form has a sense of civic scale rather than the ambience of a suburban school.
James Christou and Partners Architects conducted a lengthy consultation process with teachers, students, parents and the local community to define the brief for the new school. It was the largest consultation EDWA have ever undertaken for a new school, involving more than 300 stakeholders over sixteen weeks. The architects discarded standard assumptions about '64 square metre classrooms' and spent much time identifying the kinds of activities that would happen in the buildings, then sought appropriate design solutions.
An influential stakeholder was Jeff Phillips, Team Leader, Research & Development at EDWA, who was keen that the school's design embody the learning theory behind the new curriculum.
This resulted in the new curriculum agenda being very strongly inscribed into the school's design. Many of the Learning Areas (what used to be called classrooms) are flexible spaces which can be scaled up or down with the use of fold-back 'operable walls'. Nearly all open out onto secure courtyards, which students have considerable freedom in using as informal learning spaces. Some Learning Areas have sprung timber floors, which allow (along with light furniture that can be easily moved to the perimeter) dance, drama and exercise to be integrated into everyday learning rather than being activities that only happen in special spaces.
The Middle School is organised into four separately identified 'communities' each of 120 students and six teachers. This corresponds to a four sector floor plan, with staff studies between each two. Teachers in each sector have considerable flexibility in designing programs for their students and each learning community has its own special facilities (workshops, laboratory), so that there is less need to move to other parts of the school for specialist activities. All of this is intended to give the students a sense of ownership of the space, in contrast to the more usual practice in state schools of students changing rooms every forty minutes. This approach has been informed by education theory that suggests that learning is enhanced for middle year (early adolescent) students if they can form strong bonds with their immediate environment and teachers.
The design of the Upper School (years 10, 11 and 12) comes from a different learning agenda, providing more of a campus style environment, including two lecture theatres each with a capacity for 75 students. Almost half of the Upper School area is taken up with Arts and Technology facilities, with purpose-designed spaces for acoustic studios, rehearsal, performance, multi-media production, printmaking, ceramics, jewelry, metalwork, woodwork, colour and black & white photographic processing, plus areas for materials and equipment storage.
During the consultation process some parents expressed a desire for the school to be air-conditioned. EDWA's policy is for natural ventilation except for special use rooms and schools of the State's northern regions. Concerns about thermal comfort were addressed by using more sophisticated passive design strategies.
Post design & construction strategies
An all-day workshop for staff to explain the building's environmental control systems, many of which are user-operated, was held five weeks before move-in. This kind of instruction is particularly important for passively designed buildings that require user interaction to function optimally. Follow-up sessions would also be wise.
CAMS, the government agency responsible for procuring the school, require all buildings to be designed to minimise energy operating costs while also providing reasonable comfort for occupants.
An energy standard was developed in 1995 for all government buildings occupied by people, based on minimum performance values for the building envelope. For buildings of three storeys or less, for Perth conditions (Latitude 32 degrees south) these are:
Walls
Cooling:
Overall Thermal Transfer Value (OTTV) < 68w/m2
Heating: U value < 2.1w/m2K (for 774 Heating Degree Days)
Roof / Ceiling
Cooling: U value < 0.57 w/m2K
Heating: U value < 0.57 w/m2K (for 774 Heating Degree Days)
Additionally, EDWA requires an environmental consultant on most projects (this is explicitly stated in their publicly available 'Primary School Brief'; the High School Brief is currently being rewritten). Air-conditioning is only permitted in special circumstances, and basic passive design approaches such as the use of window shading and roof ventilators have been used for some time. At Shenton, the ambition was to apply a higher level of passive design.
Gabriels Environmental Consultants were retained to identify opportunities for passive design, including enhancement of natural ventilation. This involved consideration of prevailing climate and the site's micro-climate (particularly temperature and air movement). These factors were then related to functional needs of the different spaces. Analysis and assessment of options for sun shading, building envelope, glazing, thermal insulation and daylighting were carried out iteratively during the design process. Acoustic issues were also identified: the need to provide acoustic separation for some learning activities meant sealing some rooms and providing air conditioning. Additionally, acoustic considerations determined choice of ceiling materials in corridors.
The input of the environmental consultants resulted in some significant modification to initial design proposals. For example, an early version of the upper school layout had a curved glazed east facade to take advantage of views over Shenton Valley and to the city beyond. A review identified the potential for increased traffic noise over time, as well as a need for extensive shading of windows. This was abandoned, and the curved facade was swung around to the north.
Building envelope and orientation
The building has high thermal mass: external walls are mostly cavity brick, many internal walls are masonry, floors are concrete slab. Management of this thermal mass helps regulate summer temperatures, facilitates night cooling, and in winter, the thermal mass works to retain internally generated heat. The passive approach of exposing thermal mass to sun in winter for heating has NOT been used, as this could have created glare to levels regarded as unacceptable for learning areas.
The few external walls that are framed and clad have insulation in their cavities. R1.2 insulation is used under the roof sheeting (custom orb) along with R1.2 ceiling insulation to achieve a total U-value of less than 0.4W/m2 in summer, which is better than the CAMS minimum standard of 0.57.
The buildings are oriented with the longer axes running east / west, which allows most of the windows to be on the north and south facades. But because of their compact plans, there is still a significant amount of glazing on east and west facades. Verandahs, colonnades and dedicated shade structures protect glazing from sun and shade the thermal mass, thus helping keep interior temperatures down in summer.
Natural ventilation and summer cooling
The high occupancy level of schools (one person per 3m2) mean that significant heat loads are generated within the buildings. To optimise comfort conditions within the constraints of external climate the strategies used have been openable windows at body height for air inlet, ceiling sweep fans and operable high level ventilation.
The middle school buildings have pitched roofs with linear ventilators along the ridges, the optimal position for the stack effect. Also, to enhance the stack effect, ceilings are raked up to the ridges. The roof ventilators are fitted with operable dampers. In summer fresh air enters through doors and windows, and is drawn up to the roof space by a combination of the stack effect and the draw of the ventilators. The diurnal temperature range is sufficiently large to be able to use night cooling. This is achieved by low level louvres that are electronically programmed to open at night drawing in air that cools the thermal mass (walls and slabs). This air is then drawn up to the ridge ventilators which are left open day and night during summer (they are weather protected).
Upper
school learning area showing approach to daylighting and natural ventilation.
Note air inlet louvres and luminaries with high performance reflectors allowing
a single fluorescent tube to be used
(lights are off).
The upper school has skillion roofs, not suited to ridge ventilators. Instead, operable glass louvres are positioned high on north and south walls. These are opened by teachers during the day to expel stale hot air. Ceiling fans can also be operated to increase air movement and a sense of cooling. For night cooling high level extract fans switch on automatically to draw air out, and cool air is inducted via low level inlet louvres that operate in the same way as for the middle school.
Simple passive ventilation and cooling - body height air inlet (usually sash windows) and ridge ventilators - is common in WA schools, providing acceptable comfort conditions during standard school hours (8.30am to 3.30pm, 42 weeks a year). But the brief for Shenton College required it to be designed for extended occupancy, 8.00am to 8.00pm 50 weeks a year. The buildings will have higher summer usage than a normal school (because the summer vacation is the longest). Delayed heat transfer from the building structure (thermal lag) will effect thermal comfort in late afternoon and early evening. This was one of the reasons for installing heat extract fans.
Some areas of the school were required to be fully enclosed and acoustically separated: the two lecture theatres, a performance studio, a multi-media studio and two special needs learning areas. The latter are used for special classes for hearing-impaired students (the rest of the time they are integrated with other students), in which they do work requiring them to increase the volumes of their hearing aids, which makes them vulnerable to external noise interruptions.
Air conditioned space makes up approximately 850m2 of the total 12,798m2 of enclosed floor area. Some areas in the art and technology block have ducted extraction systems.
Heating of all multiple occupancy areas is via reticulated natural gas space heaters with automatic time off switches. Ridge ventilators and glass louvres are intended to be kept closed during winter to avoid heat loss. Smaller areas such as offices are supplied mobile oil-filled electric heaters.
Most of the Learning Areas have glazing down to floor level opening out to courtyards. In addition, highlight windows are used throughout the school for daylighting. In a typical middle school classroom these form a 600mm strip all around the room between top of parapet and soffit level. White metal has been chosen for the middle school's raked ceilings, which would improve daylighting by reflecting light. The upper school with its skillion roofs, highlight windows are on the north and south walls; white metal ceilings are used here also. Windows (both high and low level) on north facades are fitted with sun shades; where they face south no shading is required.
A north facade of the upper school showing highlight windows with shades
These two approaches depart from the more common practice in WA and NSW schools of overhead strip skylights set into the roof and combined with prismatic lens covers (see Buxton Public School case study). While delivering more daylight to desk level, skylights can also be a source of radiant heat. Getting the ratio of skylight to roof area is crucial in balancing daylighting and heat gain. To achieve this the recommended practice for WA schools is for skylights to comprise no more than 5% of ceiling area.
Sector 2 of Upper School showing large south facing windows not requiring shading
Energy conservation has informed the design of Shenton College's artificial lighting system. Most classrooms have ceiling-suspended luminaries with high performance, low brightness reflectors which allow just one 36 watt fluorescent tube to be used per fitting instead of two. Electronic ballasts are used to operate the lamps at high frequency, which improves efficacy (lumen per watt output). Lights are on a timing cycle in which half of them in each classroom turn off after four hours, the other half after four and a half hours. The rationale for the extra half hour is to allow for teaching sessions that may go over time, without necessitating turning all the lights on again. Three four hour cycles in a day allows for the school's extended hours of operation.
Detail of an upper school classroom showing use of daylighting and light coloured reflective surfaces to reduce demand on artificial lighting
There are 20 ha of protected bushland adjacent to the Shenton College site. One of the first stakeholders consulted was a local bushland lobby group who sought to have one hectare of bushland retained on the school site. This had become degraded over the years, with services having been put through. EDWA agreed to retain it and members of the local group are assisting with rehabilitation. To complement these efforts, plants for landscaping around the College were selected according to compatibility with existing bushland with a preference for fire resistant species. This is most noticeable at the entrance and on the boundaries, and applies less to internal courtyards which are grassed and more formally planted, including some non-native species.