Beyond Net Zero: Daylight in sustainable architecture

Historically, daylight has helped achieve low operational energy goals by reducing reliance on energy-intensive artificial lighting. However, with the rise of efficient LED lighting, the relative energy impact of large windows on cooling and heating can tip the balance the other way. When designing buildings that are to be used and enjoyed by people, we should aim beyond the mathematical metrics of operational energy. 

We believe that for a building to be truly sustainable it needs to be used and appreciated by people in the long term, while ensuring has a positive impact on their wellbeing. This aligns with a broader, holistic definition of sustainability, which encompasses social and economic considerations as well as energy efficiency and environmental impact. 

Natural light is associated with many psychological and physiological benefits. It has been shown to improve productivity, mood, and overall wellbeing. Workers and residents in spaces well-lit by daylight tend to be more satisfied with their environments, which enhances the long-term value of these buildings. Ensuring windows have a view (especially of the sky and nature) can promote better mental health, productivity and learning ability. 

The circadian rhythms in our bodies, which are intrinsically linked to our health and normal bodily functions, are maintained by changes in light intensity and tone throughout the day. Inappropriate lighting – where spaces are too dark and warm in tone in the day, or too bright and cool in tone at night – can change our circadian rhythms and disrupt sleep. This has negative repercussions for mood and overall health. We need exposure to bright light at the correct time of day to set our internal clocks. By using daylight as a primary source of illumination and avoiding over-reliance on artificial light, interference to these patterns can be minimised.

Daylight also has exceptional colour rendering and spectral balance, which can enhance the experience of viewing architecture and exhibits within a building. For buildings that aim to attract many visitors, such as galleries, museums and other cultural centres, this is a key consideration when deciding how a space is lit.

With natural light there are some potential risks to be mitigated through careful design, including glare, overheating in summer months, and large heat losses in winter through overglazing. In NZC buildings, daylight, views and access to the outside must be balanced against the need for solar shading and energy consumption. To solve this problem, building designers must carefully analyse and optimise the size and position of glazing in the building envelope, and ensure that the shading used is appropriate, effective and robust.