The information society promises to dematerialise society and make it more sustainable, but modern office and knowledge work has itself become a large and rapidly growing consumer of energy and other resources.
The modern glass greenhouse requires massive inputs of energy to grow crops out of season. That's because each square metre of glass, even if it's triple glazed, loses ten times as much heat as a wall.
However, growing fruits and vegetables out of season can also happen in a sustainable way, using the energy from the sun. Contrary to its fully glazed counterpart, a passive solar greenhouse is designed to retain as much warmth as possible.
Research shows that it's possible to grow warmth-loving crops all year round with solar energy alone, even if it's freezing outside. The solar greenhouse is especially successful in China, where many thousands of these structures have been built during the last decades.
Combining the old local heating practices with modern radiant and conductive heating systems could lower energy consumption, improve health, and increase thermal comfort. This is especially true for uninsulated buildings, where air heating is particularly disadvantageous. Local heating sources can be applied on their own, but can also be used in combination with air heating. This may mean, however, that thermal comfort standards need to be redefined.
However, restoring the old way of warming would not make sense without new technology. Most heating systems from the old days were inefficient, polluting, dangerous and impractical. Today, we have better options available, which can be combined in interesting ways.
The steadfast rotating fan has been employed to keep people cool since the eighteenth century, and it remains highly effective, requiring much less energy and providing more comfort than air-conditioning. Cooling people by increasing local airflow is at least ten times more energy efficient than refrigerating the air in a given space, and it also adds the benefit of a personally controlled thermal environment.
If used in combination with air-conditioning, fans could lower energy use by 30-70%, even in incredibly hot climates or during heat waves. Circulating fans, which have become very energy efficient in their design, can be readily and cheaply applied in both new and existing buildings. Recent changes in international comfort standards have paved the way for their comeback.
Architects all over the world have demonstrated the usefulness of buildings which are heated and cooled by design rather than by fossil fuel energy. What has received much less attention, however, is the possibility of applying this approach to entire urban neighbourhoods and cities.
Designing a single, often free-standing, passive solar house is quite different from planning a densely populated city where each building is heated and cooled using only natural energy sources. And yet, if we want passive solar design to be more than just a curiosity, this is exactly what we need. Modern research, which combines ancient knowledge with fast computing techniques, shows that passive solar cities are a realistic option, allowing for surprisingly high population densities.