Authored by Josée Lupien, LEED Fellow, President Vertima: This article addresses the importance of daylighting for humans and how this factor is taken into consideration within the most popular green certifications for commercial and institutional buildings in Canada.
Daylighting, as well as its absence, plays a vital role for the human endocrine system, as well as for the immune system. Indeed, it is in total absence of light, at night, that the human body produces a hormone called Melatonin in optimal quantity. This hormone contributes to the proper functioning of our immune system. However, during winter in Nordic countries, this hormone can contribute to seasonal depression if it is not elliminated properly from the body in the morning. Nonetheless, it is the exposure to enough daylighting that allows this process. Many other natural mechanisms of the body are influenced by natural light, for instance vitamin D production.
It goes without saying that we all need a daily dose of daylighting and this is all the more difficult in a Nordic country since the cold increases almost proportionally with the decrease in hours of sunshine and forces us to stay indoors. The presence of natural light in our work, home and public buildings is therefore paramount to our good health. This must be considered since the window quantity will have an impact on the building’s energy efficiency (loss of heat, overheating, lighting autonomy, etc.) and could cause uncomfortable glare and discomfort for the occupants.
Daylighting and Credits
Fortunately, building green certifications include requirements to this effect. LEED certification, along the Daylight credit combined with the Quality Views and Optimize Energy Performance credits, provide for calculations of natural light inside buildings and incorporates this requirement with Glare Controls. The calculations consider several factors, such as interior layout, finish color, glazing transmittance, window position and quantity, building orientation, building location, etc. The objective is to demonstrate that the amount of daylighting is at least 300 lux for regularly occupied spaces without having too much natural light. These calculations are performed by computer simulation. For more information, consult the USGBC Credit Library.
The WELL certification provides several Prerequisites and Optimizations in the Light category: Circadian lighting design, Solar glare control, Automated shading and dimming controls, Right to light, Daylight modelling, Daylighting fenestration. Some requirements are similar to those of LEED certification, however, the requirements for Circadian Lighting Design are new. This prerequisite states that “Light models or light calculations demonstrate that at least one of the following requirements is met: At 75% or more of workstations, at least 200 equivalent melanopic lux is present, measured on the vertical plane facing forward, 1.2 m [4 ft] above finished floor (to simulate the view of the occupant)”. The so-called warmer lights, with a longer wavelength, are more effective. More information is available here.
For the Living Building Challenge certification, it is the Healthy Interior Environment Imperative that sets out the requirements in terms of daylighting. Among the requirements of a healthy environment, it is necessary to provide views and natural light for 75% of the regularly occupied spaces. Learn more here.
There are many other certifications in the world for commercial and institutional buildings as well as for homes such as Green Globes, BREAM, HQE, etc., moreover, most of them possess daylighting requirements.
In a context where the construction industry is increasingly trying to produce highly efficient buildings, the occupant’s well-being can sometimes be neglected. It is important to keep in mind that we are engineering buildings so that they can be inhabited. Let us avoid repeating past mistakes and remember the properties built in response to the oil crisis in the 1970s, many had a glaring lack of access to daylighting.
