Before computer daylight simulations were used to optimize the atmosphere and energy in buildings, generations of builders developed simple principles to create the best windows for their site. Two lighting experts have studied these traditional openings in buildings to find inspiration for more sustainable designs today. Francesco Anselmo, a lighting designer at Arup, and John Mardaljevic, Professor of Building Daylight Modelling at the School of Civil & Building Engineering of Loughborough University, have analysed the sun and skylight variations from northern regions like Stockholm down to the equator in cities like Haiti or Abu Dhabi.
Read on to learn more about the variety of traditional windows.
The long days in summer and the short daylight periods in winter are characteristic for the Nordic countries of Scandinavia. During the summer exterior shutters facilitate sleep, with a night-like atmosphere inside the homes. The lower illuminance values in comparison with the Mediterranean or tropical regions demand openings which maximize daylight in the interior. However, people appreciate privacy. Therefore the windows are separated into two zones: the clear top part transmits as much light as possible from the sky. In contrast, the lower part with curtains or other translucent screens eliminates a direct view into the house. Contemporary architecture also shows a variety of concepts revealing how daylight in Nordic Countries plays an essential role.
The cloudy and rainy weather in London has called for windows that maximize the light. Windows with unglazed openings, which could be closed with wooden shutters or oiled cloth were common in Europe before the sixteenth century. With the development of glass technology, glass windows became more affordable. The windows' sizes were increased and the thickness of the glass decreased to optimise the daylight, and the sills are traditionally painted in white to improve the reflection of daylight into the interior. The bay-window has emerged as a specialized form to enhance light penetration for the different seasons and to make the room appear larger.
Mediterranean architecture responds with a flexible shading system to cope with the climate variations from cold and humid winters to hot, dry and bright summers. In order to reduce the solar gains in summer and block uncomfortable direct sunlight, Venetian blinds are mounted outside. Interior shutters on the inside increase privacy and soften the harsh daylight contrasts.
In contrast to Europe's complex sequence of adjustable shading layers, Japan has developed a single layer for handling daylight problems. However, with the exception of the northern island of Hokkaido, the climatic conditions in Japan are mainly comparable with the Mediterranean region. The distinctive style with translucent “shoji” screens derives from the natural and aesthetic background of Japan. Combined with the hot and humid summers, the risk of earthquakes has led to lightweight structures to permit a quick escape and simple rebuilt options. The traditional houses like those in Osaka combine diffuse “shoji” walls with heavier “amado” wooden panels, that are set into tracks to create a flexible facade. Moving the wooden panels to the side permits a view to the varandah and the contemplative garden design.
A delicate wooden latticework in the Middle East has proven to be an effective shading element for dry and sunny locations like Abu Dhabi. The openings in the Mashrabiya screens offer continuous air flow and cooling for the interior. The fine structure also reduces the glare when looking outside and allows a good view of the exterior, but looking from the outside the Mashrabiya conceals the view of the darker interiors. In this way it support the desire for privacy in the Arab culture. In the modern era, designers have transformed the vernacular wooden structure into dynamic facades.
In tropical regions days have similar length throughout the year. The sun is mainly in the highest part of the sky, and only in the morning and afternoon does the sun penetrate deeply into the houses, requiring adjustable shading panels and shutters. Therefore houses in Haiti include a buffer zone with a wooden porch or covered balcony to filter glare and block the sun during the day. They also offer protection against tropical rain showers. Two types of shutters enable flexible protection against the harsh sunlight: Top elements with horizontal hinges and lower ones which hung vertically.
For more details on vernacular windows check out the complete analysis by Francesco Anselmo and John Mardaljevic in the Velux “Daylight & Architecture” Magazine issue 19.
Light matters, a monthly column on light and space, is written by Thomas Schielke. Based in Germany, he is fascinated by architectural lighting and works for the lighting company and academy DIAL. He has published numerous articles and co-authored the book "Light Perspectives". For more information check www.arclighting.de or follow him @arcspaces.