In moderate climate-zones there is a need for heating in the winter period, while in the summer cooling of the buildings is necessary. For a long time mechanical installations were used to achieve this. But these use too much energy and moreover, they require hermetically closed buildings to work well. However it is possible to naturally cool or heat buildings by using a conservatory or atrium.

An atrium is an open, central area in the complete height of a building, which is surrounded by residence areas. In many old building cultures the atrium is used as traffic place, as meeting-place and in warmer climates as shaded inner area. When such an atrium is covered with glass the atrium can, when it has enough height, be used as a natural cooling tower. By the so-called chimney effect, in which rising warm air is removed from the area in the roof (possibly after having passed heat exchangers and possibly returned to the building after cooling). Because of the lower pressure that is created by the chimney effect ext 919s183j ernally supplied air can be led through the residence areas. In theory an atrium can contribute to the heating of a building in the winter, when the air isn't removed. But in practice it appears that the air temperature becomes too high too fast. Moreover in the current highly insulated buildings there is more often a need for cooling than heating - also in the winter months.

A conservatory is comparable to an atrium, but is situated on the façade of a building and has at least one glass wall. Which means that heating by the sun can become a problem faster. But a conservatory can - by a correct construction and usage - be used as a natural heater and cooler in a way comparable with the atrium. When the sun shines in the winter period the area, even if it freezes outside, will be heated to a comfortable temperature. In the summer the conservatory can be used as a natural cooler by the chimney effect in combination with cross ventilation from the cool side of the building.

Conservatories or atriums are often completed with plants and/or water features.
These respectively take care of an increased oxygen level and filtering of fine dust particles from the air and an increase of the air humidity. Which substantially increases the quality of the air in a building. Moreover those large, central areas form informal meeting areas - comparable to squares in a city - that can contribute to an improvement of the social climate in a building.

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The principle of thermosiphoning - the natural buoyancy of heated air or water is used to circulate heat - in a Trombe-wall is an example of a soft-technology approach to solar heating. With this technique, developed in the sixties under the direction of Professor Felix Trombe at the Centre National de la Recherche Scientifique in Odeillo (France), sunlight is absorbed on an external dark-coloured surface protected by a glazing system. The technique provides winter space heating and can be used to draw cool air through the house in the hot season.

The classic 'mass Trombe-wall' makes use of a massive wall which can store several hours of sun energy falling on the wall. During daytime heating is provided by circulating air through openings at the top and the bottom of the wall. This hot air, collected between the glazing and the wall, rises by natural convection, drawing cool room air in through the bottom vent. Thus the system circulates warm air around the room, passing its heat on to the interior. A reverse flow valve is used to prevent reverse flow after dark when it is cold.

The heat collecting capacity of the heavy wall itself is used for heating during the night-time. As it takes several hours to heat up this wall and to transmit its energy through the room, by the time of night it functions as a radiator.

During hot weather the Trombe-wall can be used to prevent heat entering the room by bringing the air moving up the wall directly to the exterior. In that case the storage wall functions as a natural convection cooler, drawing cooler air from the north side into the space.

A number variations of the mass Trombe-wall are developed to improve its performance. They include insulation, improved absorber surfaces, fans to regulate the flow of air and other capacitors like water, like in the water Trombe-wall. The thermal storage capacity (heat capacity) of water is greater than that of concrete or bricks. The use of water also ensures a lower surface temperature of the collector and so enhances the performance of the system.

A disadvantage of the system is its inflexibility. Trombe-walls are often in conflict with the requirements for view and access and may therefore be difficult to implement in a design.

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Over the past ten years the façade has grown from a defensive climate separation-construction to a much more active and complex membrane, that as an interface takes care of the separation and transition from outer climate and inner climate.

New façade-concepts provide façades that actively anticipate the difference between outer- and inner climate and that manage the inner climate together with the building installations. Not only does the demand of the designers for a transparent building-enclosure play a roll in the development of these facades, but also the strongly changing energy balance in many offices (by the increased heat production of miscellaneous machines many buildings currently deliver net heat) and the demand of many users for an individually adjustable climate and a clear view. A notable characteristic of these façades is that they actually co-operate with the installations in a building or even integrate with them to such a level that these facades become part of the installation. Although it seems contradictory the result can be that extra installation techniques are used to be able to realise an energy friendly building that can guarantee a decent inner climate.

A second-skin façade is factually a reversed climate façade: a ventilated air cavity between an inner sheet of insulated glass and an outer sheet of (usually hardened) single layer glass. A sunscreen is fitted in the air cavity, directly behind the outer sheet. Buildings in which such a façade is used are, amongst others, The new ING head office in Amsterdam (Meyer and Van Schooten), Green Building (Future Systems) and the office building in Götz (Webler + Geisler). The advantage of the second-skin façade is that the cavity can be naturally ventilated and that (inside) windows can be opened to ventilate without affecting the system too much. Another advantage of such a second-skin façade is that with tall buildings windows that can be opened by users can be applied without causing wind hindrance.

A disadvantage of a second-skin façade is that they often require an enormous amount of high-skilled techniques (not only in the façade itself but often also additional as building installation for peak loads) so these façades are often substantially more expensive than more traditional façade solutions. Only if less strict comfort-demands are used then much less extra installations can be sufficient and a second-skin façade will then, energetically seen, quickly have more advantages.

However the second-skin façade can quickly become more advantageous when in the not too long term the usage of new developments (photovoltaic cells, micro-installations and electronically manageable glass-coatings) can turn façades into a source of energy. Moreover it is to be expected that climate installations and façades will become increasingly more able to react on a local level to changing loads and demands of users by using small (cheap) sensors and micro-control techniques.

The future of smarter façades is to the sensors.

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At first glance it seems that ice as building material is only for Northern countries. But the drama of the temporality is shown to its full advantage in warmer climates.
Melting ice implies a new beginning, which is why Anders Wilhelmson Architects and Designers designed an exhibit stand of ice for the creations of SAAB. Many of the visitors of the Auto Motor Show '98 in Geneva couldn't resist the temptation to touch the living material. The melting ice lump of 3 by 12 metres was part of an elegantly designed glass construction, which showed the transparent character of the ice to its full advantage.

But ice is perishable even in the cold North of Sweden. Every year a hotel, a chapel and exhibition spaces melt away in the Jukkajarvian sun.
There are specialised architects and engineering firms that are exclusively working on ice- and snow constructions. The Finnish architect Kino Kuismanen and engineer Seppo Makinen for example are the founders of Snowhow Ltd. They strive for designs of snow and ice that optimally use of the special qualities of the perishable building material.
Another pioneer in the area of modern snow building is the architect Kako Nordstrom. He has designed a patented system in which spans of 10m wide can be made. Snow is sprayed in layers on moulds. After hardening the mould is slid further like a tunnel shuttering, so long sheds can be built. The modern snow domes are, in contrast to Igloos, more like tent constructions. The Eskimo's stack blocks of ice to small domes. The modern snow builders make thick blankets of snow that are held high with tent poles of ice. These tent poles are built from slices of ice that are cut from the river.
While for Eskimos they are essential to survive, ice- and snow constructions in countries such as Sweden, Finland and Japan are an important tourist attraction. But it is cold in these ice palaces. While the Eskimos could 'heat' their homes to a temperature of approximately 15 degrees by body heat and the heat of the oil lamps, the modern snow buildings are cold cells in which you can only comfortably stay with modern ski clothing.

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That the experiments aren't limited to a small scale became clear at the 1992 world exhibition in Seville. A tower built from prefabricated paper elements marked the entrance of the area. The landmark had a diameter of 13m and a height of 33m. The biggest challenge was to make up for the large pressing- and pulling powers in the lower construction of the tower. Enough stability was obtained by aiming the sidewalls of the three-dimensional prism shaped elements to the axis of the tower. The tower was entirely biodegradable so it was recycled after the exhibition.

Still a step further is the proposal for the world exhibition in Hanover designed by the Japanese architect Shigeru Ban that has applied himself to building in cardboard. His emergency homes for Kobe are now world famous. These emergency homes for the earthquake victims in Kobe are from paper tubes. The 'Paper Log' constructions have a roof from canvas which diffusely lights the interior. The foundation consists of sand filled crates.

Shigeru Ban's proposal for the Hanover Messe consists entirely of paper. The building takes up a surface area of 3600m2. The more-stories high building of 89m long and 42m wide will come on a basement. The span of the carrying construction amounts to 35 metres and consists of bent beams of 12 centimetres thick pressed paper. The roof is a membrane of textile and paper synthetics.
The building serves from June 1st until October 31st as the Japanese pavilion in the Hanover Messe. It looks good on paper...

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