ÐÇ¿Õ´«Ã½

There seems little doubt that people prefer to live and work in sunlit spaces. Recent research suggests that building occupants are healthier if they do so. Yet designing to exploit the therapeutic properties of direct sunlight is something of a lost art. It used to be common practice to arrange buildings to take advantage of the sun. But today the health benefits of solar design are not widely recognised with the result that solar architecture is now primarily the architecture of energy efficiency rather than health. There are a number of reasons for this; the main one being that when sunlight falls from favour with the medical profession – as it has done over the last fifty years – there is little incentive for architects and engineers to make provision for it.

At other times and in other cultures sunlight was valued as a medicine, and this had a direct and often very profound influence on building design. The Ebers Papyrus, one of the oldest surviving Egyptian medical texts recommends exposure to the sun, and some of the most distinguished figures in Greek, Roman and Islamic medicine used sunlight to prevent and cure disease. So, not surprisingly, in the ancient world it was widely held that sunlit buildings were healthier than those that excluded the sun's rays. Under Roman law there were rights to sunlight, and solar access litigation continued until the final days of the Roman Empire.

However, with the fall of Rome, and then the Dark Ages, the principles of solar design were largely ignored or forgotten. Doctors no longer thought that sunlight was beneficial to health, and so there was no reason for architects to either. Consequently, the advantages of getting solar radiation into buildings to prevent disease were not appreciated for more than a thousand years. Indeed, it was not until the end of the 19th century that sunlight again came to be regarded as important to the well-being of building occupants.

Sunlight and depression
Florence Nightingale was responsible for some of the first sunlit hospital wards of the modern era. As she wrote in her Notes on Hospitals in 1863: 'Direct sunlight, not only daylight, is necessary for speedy recovery'. She also insisted on sunlight because she believed it had a 'purifying effect', and current research certainly supports many of her assertions about the sun and its favourable impact on hospital patients.

For example, depression is the most frequently diagnosed symptom and the cause of more hospital admissions than any other psychiatric condition. According to the World Health Organisation, depressive disorders are the fourth leading cause of ill-health among adults worldwide, and by the year 2020 severe depression will be second only to cardiovascular disease as the largest cause of death and disability. Estimates of the number of people who suffer from the seasonal form of the condition vary, but Seasonal Affective Disorder (SAD) is a widespread problem; particularly in its milder form, the so-called 'winter blues'.

The idea that lethargy, sadness and despair can be triggered by low light levels is an old one. Yet it was only in the 1980s that the link between light deprivation and depressive illness was scientifically proven. Light therapy has since become an effective treatment for seasonal depression and there is growing evidence that light therapy can have a positive effect on non-seasonal depression.

Relief from the symptoms of depression can follow relatively short exposures to light at about 10 000 lux. In a typical building daylight and electric lights provide somewhere between 150 lux and 600 lux, while in a sunlit room there can be as many as 60 000 lux falling on a plain surface. So a building which admits significant amounts of direct sunlight is much more likely to maintain the biological rhythms and emotional stability of its occupants than one that does not.

This was demonstrated in 1996, when it was reported that clinically depressed patients in sunny hospital wards fare better than those in dull rooms. Patients with severe depression at a psychiatric hospital who were fortunate enough to be put in sunlit wards and, as a result, got involuntary light treatment from the sun were discharged more quickly than patients in rooms which received no direct sunlight. There are other potentially life-threatening conditions which improve when patients are put in sunlit rooms. Heart attack victims fare better in them than in sunless north-facing ones. But perhaps the most significant benefit of admitting sunlight is its bactericidal effect.

Sunlight and bacteria
Sunlight is a potent bactericidal agent – even when it has passed through window glass. So in the years before antibiotics became widely available, hospital wards were designed to admit direct sunlight to reduce the risks to patients of cross-infection. Today infections picked up in hospitals cause more deaths in the UK than either road traffic accidents or suicide. At least 5000 patients die each year as a direct result of hospital infections, and a further 15 000 or more deaths are caused by complications due to an infection caught after treatment. Methicillin-resistant staphylococcus aureus is the most common cause of death from hospital-acquired infection in the UK and a number of other bacteria that cause hospital infections are resistant to antibiotics. In addition, strains of tuberculosis have emerged which are resistant, and these are becoming established in the developed world and elsewhere, posing a serious threat to international public health. If some of the more pessimistic warnings about drug-resistance are accurate there may be a great deal to gain from a return to a form of solar design which promotes health and hygiene.

From historical evidence and contemporary medical research it is clear that sunlit rooms can be much healthier than rooms which exclude the sun's rays. However, in marked contrast to Imperial Rome, there is no right to sunlight in this country. Consequently buildings are not arranged to take as much advantage of the sun's therapeutic properties as they might be.

The Lister Wing of Benenden Hospital in Kent, which was designed in the inter-war years makes much use of natural light. Established to house patients suffering from tuberculosis, architect Thomas Smith Tait arranged the two-storey block with wards along the fully glazed southern facade; opening onto a terrace and first floor balcony. This gave direct access to sunlight and, weather permitting, allowed the windows to be open and patients to lie in the open air. This can be contrasted to a recent addition on the site. The new clinic, designed to compliment the listed Lister Wing, makes use of a wall of fixed louvres standing in front of the south-facing facade to control solar gain.

Designing for sunlight
As some 70-90% of the costs of running many organisations consist of the salaries of the work-force, the financial returns for employers who specify sunlit spaces for their employees could be considerable – potentially far more than their energy costs. Unfortunately improvements in building fabric insulation standards militate against sunlight penetration: solar gains become more significant and more difficult to accommodate as U-values are tightened. Under these circumstances it is more convenient to achieve energy efficiency by imposing strict controls on internal conditions – and excluding the sun – rather than by designing for sunlight penetration.

Such an approach prevents building occupants from enjoying the benefits of living and working in sunlit spaces, and may result in significant health and productivity costs in the longer term. The provision of direct sunlight in buildings is one of the greatest challenges to face any designer, particularly if the intention is to admit enough light of sufficient intensity to have any impact on the well-being of occupants. But as the old Italian proverb points out: "Where the sun does not go the doctor does".