Ice And Snow

The potential of snow as an insulating material against walls and on roofs has been used in the north throughout history. One of the main reasons for having a grass roof is that in appropriate climates it retains snow for longer. Ice is also a structural building material of interest in colder climates. The former Soviet Republics have a special category of engineering, 'engineering of glaciology': the design of ice structures such as roads and bridges in areas of permafrost. Many of these structures are now in danger due to climate warming. In recent years there has also been a keen interest in ice hotels, both in Scandinavia as well as Canada, Romania and Switzerland. These are seasonal, and as long as natural ice is used is an excellent environmental material.

Ice hotel in Jukkasjarvi, Finland. Design by KTH students. Photo: Ben Nilsson/Big Ben Productions.

Ice hotel in Jukkasjarvi, Finland. Design by KTH students. Photo: Ben Nilsson/Big Ben Productions.

5.3 AIR

Ice church in Jukkasjarvi, Finland. Architects: Vonk, Berg, de Schootand Vroom. Photo: Big Ben Productions.

In the Earth's atmosphere the percentage by weight of the different gases is as follows: Nitrogen 78%, oxygen 21%, argon 0.93%, carbon dioxide 0.038%; plus smaller amounts of hydrogen, neon, helium, krypton and xenon, as well as water vapour and various pollutants.

At very low temperatures air becomes a slightly blue liquid. From this state oxygen and nitrogen can be extracted by heat. Nitrogen can be used for the production of ammonia by heating hydrogen and nitrogen to 500-600 °C under a pressure of 200 atmospheres and passing it over a catalyst, usually iron filings. However, today ammonia is mostly produced from natural gas. Ammonia is an important ingredient in the production of waterglass via soda, and as the main raw material for the production of ammonium salts, which are used as flame retardants in some insulation products. By reacting with hydrocarbons it forms amines that are used in the production of a whole series of plastics.

When a material oxidizes it forms a chemical compound with oxygen. This is an exothermic reaction. In construction this is a very common process in metals, known as rust or corrosion. The process is electrolytic. In many cases this oxidization is not a welcome process, so metals in construction are often treated with a protective coating. Rust on reinforcing bars for concrete, on the other hand, is to an extent welcome since it increases the bond with the concrete.

Other compounds in the air can also break down building materials, including natural carbon dioxide and air pollutants, such as sulphur dioxide and soot.

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