At the heart of our lighting design we should place the central concept of the relationship between day and night, light and dark that lies within our most natural rhythms.

This is a complex discipline in that the direction of the sun at given times of the day & the year, the orientation of a building, weather conditions, the quality of glazing and many other variables will all influence the quality and amount of light that reaches the subject. I hope to touch on some of the factors of importance when starting your consideration of lighting in the healthy house.

Although little conclusive evidence is as yet available, studies suggest that the negative health consequences of improper lighting may include; stress, headaches, fatigue, as well as decreases in sexual function and increases in anxiety levels.

In considering light, we are not only interested in the effects of over or under illumination, but also the spectral composition of light. Research indicates that full spectrum lighting may, in the same way as natural sunlight act to boost the immune system and perhaps provide a positive health benefit.

What is full spectrum lighting?
The sun is a huge emitter of electromagnetic radiation (EM). This EM radiation has many wavelengths each of which has differing properties. Visible sunlight occupies a range of wavelengths that our brains interpret as the primary colours and that when combined make up white light or daylight. Full spectrum lighting includes the full range of visible sunlight. Tungsten bulbs, for example are stronger in the red part of the spectrum and weaker in the blue so can tend to make distinctions between dark blues and black difficult.

So what do we need to avoid and what should we look to include in our healthy house lighting design?

Avoid

• Glare caused by light sources (including the sun) striking reflective surfaces.
• Flickering light sources.
• The inability to vary light levels to provide adequate levels of lighting for tasks, for example, over-lit relaxation areas or under-lit work areas.

Include

• Daylight wherever possible – our sight has evolved to use it so works best with it! There are other health benefits to direct sunlight such as the production of vitamin D.
• Where daylight is not available, full spectrum lighting options should be considered.
• For occasional or zonal lighting consider low energy LED lighting options.

Bear in mind that windows of one of the greatest sources of heat loss, so glazing systems need to be as energy efficient as possible and excessive provision of glazing avoided. Glare and over-heating of rooms are also a potential risk on sunny days.

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