Testing times

There is a requirement for significant improvements in the UK's schools infrastructure, and the early 21st Century has witnessed the first steps of this process. The government funding being ploughed into the new tranche of school buildings amounts to around £35 bn to modernise 3500 secondary schools in England by 2015 (this does not include primary schools that are likely to have a similar figure).

As designers and constructors of the new school buildings we have a responsibility to deliver real improvements to enhance the learning environment. This requires a step-change in their design and operational standards. It is clear that the new requirements of performance and teaching methods are determining the drive to innovation and a return to first principles in developing design solutions. Furthermore, substantial demands are now being placed on head teachers and teaching staff as their need to become professional clients grows, especially during the briefing and decision making stages of procuring construction projects. It is time to get radical, particularly for consultants and contractors in developing our design approach and construction methods in meeting the new needs of the schools sector.

First steps
Help is needed to ensure that the buildings being designed now will be able to perform adequately for the next 50 years and beyond. By this time, the predicted impacts of climate change, differing resource availability and demographic development will test the sustainability of our thinking severely. Design guidance and assessment tools are changing to reflect new approaches to design and construction of schools.

The initial driver behind recent changes in the design of new schools was Building Bulletin 87 Guidelines for environmental design in schools (BB87) first published for the Department for Education and Employment in 1997. This guide addressed the guidelines for environmental design in schools.

The first phase of schools designed in accordance with BB87 have now been operational for a few years – allowing time for the initial issues associated with commissioning and operation to be ironed out.

New guidance
It is clear that although BB87 offered some fairly strict and robust design routes to follow, there were still significant areas that needed to be addressed. In May 2003, the second edition of BB87 was released to address the key changes that are required.

Some of these are due to regulation changes from other sources eg Approved Document Part L2 (ADL2), and some result from feedback from the initial wave of new schools. The following highlights some of the key stages that have been updated and the impact of these on how we design, construct and operate the new school buildings.

Overheating
The guide starts with a discussion of the proposals under the new BB87 construction standard and the Building Regulations ADL2. Fundamental to this discussion is the requirement for summertime temperatures not to exceed 28°C for more than 80 hours per year. Apart from this being an intolerably high temperature, the impact of this requirement raises further questions on how we are to comply with this without taking a simple way out by reaching for a refrigerant cooling system. Issues that can work for us here include orientation, solar shading, heavyweight internal construction and substantial air-change rates.

However, the ways in which schools function, namely teaching methods and learning tools, are changing rapidly. Many new schools are requesting that provision is made for full IT use throughout the teaching spaces. BB87 suggests that this is achievable given thermal mass and five pcs per classroom. But the likely impact on internal temperatures of every pupil having an electronic tablet, that's 30 tablets, is such that it is very likely to exceed 28°C for more than the allowable 80 hours. Assumptions are made that natural ventilation will be used for teaching spaces that have limited equipment. The definition of 'limited equipment' is suggested as 'up to five pcs with crt screens, a laser printer and an ohp or projector per classroom'.

BB87 hints at recognising that the future electrical and thermal loads in teaching zones will be such that natural ventilation is inadequate to maintain comfortable internal conditions. The solution suggested is that air conditioning and mechanical ventilation may be required and defines specific power consumption figures for the selection of this equipment.

A similar dichotomy is being felt in healthcare design where 35-55 GJ/100m³ design energy targets are being driven down, while the operational practice is becoming more and more dependent on electronic processes and methods. These practices are both consumers of electricity directly in the equipment, and indirectly in the cooling systems required to deal with the heat produced by this equipment. However, that's for another article!

There are three routes to demonstrate compliance of ADL2:

• Elemental method, together with advice from BB87 (2003).
  
• Whole building method described in BB87 (2003) to achieve <5 kgC/m²/year.
  
• Carbon emissions calculation method recommended for innovative or passive designs.

Thermal performance
With improved U-values and the anticipated casual gains that are likely to be produced by the increase in IT equipment, the net heating requirement for the new school buildings will be reduced. Furthermore, if a simple system of mechanical ventilation with heat recovery is used in the winter months, the heat loads associated with ventilation will also be reduced. This in turn will mean that heat emitters will become much smaller and allow more space on walls for equipment storage or displaying students work. Reference is made to recirculation of warm air in spaces that have higher ceilings through the use of 'punkah' fans as a simple method of getting heat to where you need it most. Improved roof insulation would also be a fundamental consideration in these instances.

In order to reduce summertime temperatures the application of exposed thermal mass on the ceiling soffits is recommended to smooth the degree of daily temperature swing, and provide capacity for thermal storage. This implies that the architects and structural engineers will need to pay specific attention to the type of upper floor/roof slab systems that are installed, to reduce capital cost expenditure. The increase in casual gains from IT equipment is recognised again, and the guide suggests that special consideration may be required. This 'special' consideration may be suggesting a drive towards greater use of air conditioning and mechanical ventilation systems that will result in increased capital cost and ongoing energy and maintenance costs.

The suggestion is made that a full classroom of pupils will compensate for all fabric loss and a major part of the ventilation losses. This is fine for a full classroom, but what about classes that are less occupied, for example a sixth form class? The main question that arises here is how exactly is the ventilation to be provided?

Ventilation and indoor air quality
The provision of adequate fresh air for odour control and improvement of air quality, in order to ensure that the pupils are comfortable in their environment is imperative. The recommendation of 8 litres/s/person is made, and it is also suggested that the preferred method for providing this air is through natural ventilation. In the majority of school buildings, natural ventilation is the primary method that has been adopted to provide fresh air ventilation to teaching spaces.

In order to achieve the fresh-air ventilation rate of eight litres per second per person, via natural means, for say thirty pupils, would require a net opening in the facade of around 0·34 m x 0·34 m (8 litres/s/person x 30 = 240 litres/s, @ 2 m/s velocity, opening area = 0·24/2 = 0·12 m², = 0·34 m x 0·34 m).

During the summer this represents a fairly straightforward solution in terms of providing air quality. However in the winter, the air will be cold and an opening this size would create issues with the control of cold draughts and infiltration losses. In practice, this tends to lead to the windows or openings being closed either partially or completely to reduce the impact of noise and cold draughts While this was less of a problem with older schools that had very 'leaky' envelopes to allow for beneficial background ventilation, newer construction methods produce better sealed buildings with less air leakage. Therefore, the required air volume would not be supplied and the air quality would deteriorate, leading to lower levels of pupil concentration levels and learning ability. Other factors would include humidity, allergens and volatile organic compounds, which could lead to asthma and the spread of common colds/viruses. Furthermore, with opening windows or vents it is becoming increasingly difficult to comply with acoustic guidance in BB93 Acoustic design of schools etc. These are serious risks that need to be addressed.

Mechanical solution?
In order to guarantee 8 litres/s/person especially during winter months a simple step-change solution would be to provide low cost, mechanical ventilation plant with heat recovery. The heat recovery aspect is essential in making this solution cost-effective in terms of running costs with an estimated payback between two and five years. A CO₂ level sensor would be used to control the operation of the plant – meaning that it would only run when required. The specific fan power should be low (1·0-1·4 W/l/s) to reduce running costs and CO₂ emissions and the heat recovery device should have a high efficiency (70-85%). Furthermore, provided the acoustic environment is satisfactory, the unit would only run during the heating months – October-April, leaving natural ventilation to take over during the more climatically favourable months.

Currently throughout the UK, there are few precedents of using mechanical ventilation for school buildings – the most notable is perhaps Greenwich Millennium Village school. This is due in part to the previous regulations being less onerous and also architects and qs's reluctance to allow space or cost. However with the new BB87 and BB93, we are likely to see more of these systems implemented to comply with the regulations and a radical step change to school design will emerge.

Summary
The pressure on pupils to perform is growing with tests being carried out from a young age. The results are also monitored and assessed by the schools to show how well their pupils are progressing. Current trends suggest that in the near future this reporting procedure is likely to increase, meaning that the performance levels, and funding gaps, between high achievers and low achievers will grow. This will place lower achieving schools in a vulnerable position.

This system and approach could see a real change in the way new school buildings are designed and managed. Our understanding of both needs to expand through facility management feedback and in-service evaluations that inform our designs in terms of functionality, maintainability and social and sensory impact. With the new BB87 and BB93, and the BREEAM for Exemplar Schools currently under development, the new schools should provide better environments for learning, and reduce energy consumption. In order to achieve this, we will need to make our buildings work harder to reduce the thermal loads.

It needs to be recognised that the educational building sector provides a substantial contribution to the economy at present, but more importantly has a significant impact upon quality of life. It is clear that we need to understand the relationships between health, education and environmental conditions and the immense impact on our future prospects.