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Rooflights Shine a Light on Learning Environments

Mardome Circular & Premier Domes, Castle Park School Under the proposals for the revisions to Part L, announced this March, the government has put forward a more flexible, aggregated approach for non-domestic buildings, including schools. Here Bill Hawker, Technical Director of Brett Martin Daylight Systems discusses the impact that lighting through rooflights plays on the energy performance of school buildings and looks at the role of natural daylight as a route to achieving energy savings and therefore carbon reductions.

Instead of a flat 25% improvement in energy emissions across all buildings, the new proposals to review Part L suggest that all non-domestic buildings should be subject to a more flexible assessment, depending on the building type. For new school buildings this is set at 27%. It has been widely accepted for years that it is the lighting element of any building that consumes the majority of energy and therefore contributes most greatly to the building’s carbon footprint. It is therefore likely that it will be essential to address services such as lighting to meet this 27% target, and if done correctly this target can not only be met but also exceeded.

In fact, the DCSF has recognised both the need to reduce energy use in the school environment and the importance of future proofing school buildings against further legislative requirements. It also requires that all new and refurbishment school building projects within its capital programmes achieve a BREEAM rating of ‘excellent’ for new school buildings and at least ‘very good’ for refurbishment projects.

By reducing the amount of artificial lighting needed in school buildings by correct use of abundantly available natural light, made possible through the specification of systems that help to introduce the effective use of daylight in buildings, those responsible for school buildings can not only significantly improve the lighting energy use of the building but also maximise the design potential of natural light, improving the interior environment and having a positive impact on student welfare and performance too.

Building Bulletin 90, set out by the DfEE specifically addresses the lighting requirements for school building design. It states: ‘The school designer should assume that daylight will be the prime means of lighting when it is available.’ With reference to new school buildings such as those being designed and constructed under the latest wave of BSF funding, it is easy to see how these buildings serve as working examples of sustainability in action.

However the challenge for managers and engineers of existing school buildings is to integrate daylighting solutions into the current school fabric. Typically the windows of existing school buildings are too small and too few, while major assembly spaces have little or no source of natural light at all. In its report ‘Assessing Secondary School Design’ CABE found that over 50% of the schools completed in the last five years were mediocre or poor, performing badly on basic issues such as natural lighting and ventilation. A constant point of failure was the provision of natural light in circulation areas such as corridors and walkways.

CABE’s ‘Picturing School Design’ paper emphasises that: ‘The natural light in the building should be of a high quality’. In fact in order to substantially reduce the need for artificial lighting, all key spaces in the school building should be daylit for most of the year, with rooms located to make the most of the available natural light. Because rooflights enable the introduction of daylight deep into the interior of buildings, they can be used to draw daylight into areas where windows would not be effective.

Part L 2006 Building Regulations also sets carbon emissions targets and it has been clearly demonstrated that installing up to 20% of the roof area in rooflights (with a maximum U-value of 2.2W/m2K) is a major contribution to meeting these targets, and presents school building managers, engineers and end users with a practical solution to ensuring that lighting levels remain adequate while reducing the need for artificial lighting.

The DCSF has issued ‘Standard Specifications, Layouts and Dimensions 5 – Roof Coverings in Schools’. This recommends that daylight systems should be used in conjunction with automatic lighting controls, ensuring that when daylight levels are highest the artificial lights are switched down or off and when required they can be switched on automatically, avoiding the risk of teachers and pupils misusing the electric lighting.

It is vital that, when introducing new lighting plans, end users are informed of the reasons why and understand fully how to ensure they operate to the best effect – there is little point in installing daylighting solutions in classrooms, only for users to continue switching on artificial lighting. Therefore it is important to create lighting plans that are suited to individual schools, sites and locality. Lighting requirements will vary according to region, building orientation, hours of available daylight and the intensity of the sunlight. A specialist technical partner will take all this information and ensure the design solution meets the specific needs of each individual school project.

There is concern over the potential for excessive solar gain, which needs to be addressed. Independent research by scientists at Oxford Brookes University has demonstrated that high levels of natural light can be achieved through rooflights, without creating a problem with solar overheating. The optimum level of rooflights will depend on the window area, internal gains in the space being considered, levels of ventilation and air movement, and should be addressed at design stage. Typically rooflight areas up to 12% can be specified without concern, whilst significantly higher areas are appropriate in many cases. A successful school building daylighting scheme will feature spaces that are orientated so that solar gain and glare are controlled effectively. Such a solution will help to minimise energy use and carbon emissions, providing a comfortable learning environment that benefits from natural light the majority of the time.

There are important physiological benefits to incorporating natural light into the school environment. Plenty of research points to a positive correlation between concentration, performance, results and the improved natural daylight in educational environments. Increasingly research is demonstrating that the use of natural light impacts the performance of those who use a school building. A study by the Heschong Mahone Group looked at the effect of daylight on human performance and found that students progressed faster in their studies when their classrooms were lit with natural daylight. Supporting this is evidence from a study by Paul Grocoff Ph.D, which found that students felt ‘the worst’ under traditional fluorescent lighting and ‘the best’ under natural lighting. It is therefore critically important that the design, planning and construction of any school is based on the understanding that the facilities influence the learning climate.

All this evidence points out that including rooflights significantly reduces the need for artificial light, dramatically cutting energy consumption, reducing the carbon footprint of the school building and improving the internal environment for wellbeing and better student performance. There are of course considerations to take into account, both for new school building design and for refurbishment of existing buildings.