Effective daylighting is an essential part of modern educational architecture. Research from across the globe shows that access to natural light can raise academic performance and improve student wellbeing. It can also help to reduce reliance on artificial lighting, minimising energy usage and costs.
However, daylighting design is about more than simply installing larger windows. It requires a holistic approach, considering everything from the building orientation to the choice of materials, such as insulation, which can impact construction depths.
How does access to light effect students?
At a most basic level, the natural light cycle maintains our internal body clock (circadian rhythm). This keeps us awake and alert during the day and improves our quality of sleep at night. Young people are particularly sensitive to any disruption to this rhythm due to their smaller pupillary sizes and weaker melatonin-suppression.
Within the classroom, diffuse natural light can help students to read and understand learning materials. It contains the full spectrum of visible wavelengths, allowing improved colour rendition. It also avoids potential problems such as flickering and noise emission which can occur with tube lighting.
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 scores1.
What factors affect daylight design?
Daylighting design is a careful balancing act. 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 Education Funding Agency (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;
- wall thicknesses; and
- glazing sizes and detail.
The choice of insulation for a project, and in particular its thermal conductivity (or lambda value)
, can have a notable impact on these last two parameters.
How can insulation impact natural light?
By specifying insulation materials with lower thermal conductivities, it is possible to achieve a desired U-value with a reduced thickness of insulation.
In a previous blog, 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.K.
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.
Peutz BV have now completed further research looking at cavity wall constructions. This analysis, which is explored within our Daylighting White Paper, shows that similar improvements in internal natural light levels can be achieved by specifying Kingspan Kooltherm K106 Cavity Board or Kingspan Kooltherm K108 Cavity Board over less thermally efficient insulation.
1. Tanner, C. (2009) Effects of school design on student outcomes, Journal of Educational Administration, Vol. 47 No. 3, 2009. pp. 381-399.