The right to natural light has been recognised within UK law since the 1830s. Today, we understand that good quality daylighting can provide a wide variety of benefits including improved sleep/waking cycles and reduced symptoms of Seasonal Affective Disorder (SAD). Access to natural light is particularly important for young people and there is a growing body of evidence suggesting it is not only beneficial for student wellbeing but can also improve attainment. As such, when designing education spaces, it is important to carefully consider all factors which can impact daylighting – including the insulation specification.
Why Natural Light?
Guidance from both the Education Funding Agency (EFA)
and Chartered Institution of Building Services Engineers (CIBSE)
suggest that natural daylighting should be the primary source of light within education spaces. There is a clear operational advantage to this strategy. By providing improved levels of daylight, it is possible to reduce reliance on artificial lighting – minimising energy demand and long-term running costs.
However, the advantages of improved daylighting extend far beyond energy efficiency. Natural light helps to reinforce our circadian rhythm, making us more alert during the day and improving our sleep at night. Studies have shown that young people are particularly sensitive to disruptions to this rhythm as a result of their smaller pupillary sizes and weaker melatonin-suppression.
Natural light can also make it simpler for students to see and understand learning materials. It is more diffuse than typical artificial ceiling lights, providing better illumination throughout a space. It also contains the full spectrum of colour wavelengths visible to the human eye, allowing improved colour rendition. Additionally, it avoids potential problems associated with some artificial lights, such as flickering, which can cause headaches and eyestrain
Research has shown that, as a result of these factors, provision of good quality natural light can have a notable impact on student attainment. A study of over 21,000 US students in 1999 showed that those with the most daylight in their classrooms progressed 20% faster on maths tests and 26% faster on reading tests in one year than those with the least. A further study of 71 elementary schools provided additional evidence that good lighting provision, both from natural and artificial sources, significantly influenced pupils’ reading vocabulary and science test scores.
Achieving Good Quality Lighting
Of course, effective daylighting design is not simply about maximising the amount of light within a space. Too much light can be just as detrimental as too little, potentially leading to issues such as heat spots, glare and overheating.
To find a balance, the EFA advocates a Climate-Based Daylight Modelling (CBDM) approach. Through the use of 3D modelling, this methodology attempts to maximise visual comfort across all areas of a school. It considers a vast array of parameters including:
- local weather data;
- the size and orientation of the building and internal spaces;
- internal details such as ductwork, blinds and acoustic panels;
- reflectance of internal materials;
- glazing sizes and details; and
- wall thicknesses.
The choice of insulation for a project, and in particular its thermal conductivity, can have a notable impact on these last two parameters.
By specifying insulation materials with lower thermal conductivities, it is possible to achieve a desired U-value with a reduced thickness of insulation.
In the Summer 2018 issue of Insulation Insight, we looked in detail at research from Peutz BV
which considered how the use of insulation with different thermal conductivities could impact the average daylight factor (ADF) within a space. The research compared Kingspan Kooltherm K15 Rainscreen Board with lower performing mineral fibre insulation in three different rainscreen configurations designed to achieve U-values of 0.11 W/m².
K, 0.15 W/m².
K and 0.21 W/m².
In all scenarios, Kooltherm K15 Rainscreen Board allowed the target U-value to be met with a reduced construction thickness (and consequently slimmer window reveal). The modelled results showed that this in turn led to improved daylighting within the space.
A further advantage of selecting insulation materials with low thermal conductivities — such as our Kooltherm K100 range — over poorer performing alternatives, is that they may allow the glazing area within an element to be increased whilst still meeting the target U-value.
BS 8206-2: 2008 (Lighting for buildings. Code of practice for daylighting)
EFA daylight design guide, Education Funding Agency (2014)
Lighting Guide 5: Lighting for Education, CIBSE
M. Winterbottom, A. Wilkins, Lighting and discomfort in the classroom
Tanner, C. (2009) Effects of school design on student outcomes, Journal of Educational
Administration, Vol. 47 No. 3, 2009. pp. 381-399.