Lighting (Natural and Artificial)

CONTEXT

In addition to making it possible to see, light affects the human body in other non-visible ways. The biological rhythm of human beings is programmed in accordance with the natural cycle of light during the day and darkness during the night, which lasts approximately 24 hours and is known as the circadian cycle.

Two types of lighting can be distinguished: natural and artificial. All lighting, not just natural light, contributes to the circadian rhythm of our bodies. Taking into account that we spend around 90% of our time inside, it is necessary to condition the lighting in public buildings with the aim of favouring visual perception and the circadian cycle in order to ensure the correct execution of tasks and the safety and wellbeing of the occupants of these buildings.

The interior lighting of a building is considered to be correct if it meets three basic needs: comfort, productivity and safety. Deficient lighting, however, may have ad-verse effects on people’s biological rhythms and productivity. It may also cause visual fatigue, eye pain, headaches, concentration problems and insomnia. Three key factors should be taken into account in relation to visual comfort: visual acuity (clarity), sensitivity to contrasts, and efficiency of ocular functions. These are the factors that determine visual performance.

In the case of artificial light, its impact on the electricity bill must be taken into ac-count, given that in offices and facilities it generates considerable consumption, sometimes more than that of cooling and heating. Notwithstanding, it is important, wherever possible, to design buildings with natural lighting in mind, given that the presence of natural light enhances the sensation of wellbeing and increases performance.

OBJECTIVE

Define criteria for the provision of suitable levels of good natural and artificial light so that day-to-day tasks can be properly carried out in facilities without affecting the circadian cycle.
Teach people to responsibly use artificial light and avoid unnecessary consumption.
Improve energy efficiency in lighting.

PROPOSALS AND RECOMMENDATIONS

Although it is not compulsory, the right to natural light should be guaranteed in all interior spaces occupied for long periods of time. Natural light should always be the main source of light.
Foster exposure to daylight and views of the outside world, limiting the distance of workstations from windows. The distance between workstations and windows should not be more than 7.5 m.
Foster visual acuity through the definition of optimal levels of lighting in accordance with the type of use of the space and the tasks to be carried out. An ambient lighting level of 300 lux is sufficient for the majority of tasks. Workstations and desks should maintain an average light intensity of at least 215 lux, measured on a horizontal plane 80 cm from the finished floor. In accordance with the regulations, this light intensity value may vary in accordance with the activities to be carried out: for example, a value of 500 lux is required in offices (writing areas) and in libraries (reading areas). Lighting could be dimmed in the presence of daylight, but it should not depend on natural light to comply with the recommended level; use of different types of efficient lighting: replacement of halogen and fluorescent bulbs with low-consumption LED bulbs.
Guarantee that the interior lighting system is distributed into different zones with a surface area of less than 45 m2 that can be controlled independently. Artificial lighting regulation systems must be automatic or easy to operate by building managers.
Avoid dazzling by using protection systems (such as curtains or blinds) so the oc-cupants are not directly affected. In south-facing openings, an awning of approximately 1 m prevents the effects of direct sunlight. In east- or west-facing openings an awning is not efficient once the sun shines horizontally on the windows. Vertical blinds or curtains that respect visual transparency should be installed.
Foster the presence of sunlight by means of automatic light dimming systems.
Install automatic presence detection sensors in frequently used zones and in less used zones (toilets, service areas, etc.) to dim the lighting to 20% (or switch it off completely) whenever these spaces are not occupied.
Inform the occupants of the building of the results of good lighting management (energy saving, high productivity levels, sensation of security and comfort).
Light tubes: they use heliostats to harvest sunlight and they transmit it without transmitting heat. • Vertical skylights: they prevent direct light in summer and enable light to get through in winter.

REFERENCE EXPERIENCES

• International Well Building Institute "Well Building Standard - Light".
Document "Aprovechamiento de la luz natural e la iluminación de edificios". Comité Español de Iluminación
Philips, video "Adaptive Healing Rooms".

LEGISLATION

Codi Tècnic de l'Edificació. Document Bàsic d'Estalvi d'Energia, amb comentaris del Ministeri de Foment.
UNE 12464.1. (2003) Norma europea sobre la il·luminació per a interiors.
Disposicions mínimes de seguretat i salut en els llocs de treball RD486 / 1997 de 14 d'abril
HE3. Eficiència energètica de les instal·lacions d'il·luminació (juny 2017)