The igloo's apparently simple design masks an engineering marvel and could teach modern builders a thing or two, says Dan Cruickshank, who helped build one for his new TV series.
Last year I flew into the Arctic, heading for the east coast of Greenland. My plan was to see, indeed to help make, an igloo.
This inspirational and economic miniature-engineering marvel has long fascinated me. How did the igloo evolve, when and where? No one knows for sure but traditionally they were built only by specific Inuit communities in relatively small areas of Greenland and Canada, and were used only for temporary accommodation in winter months, or by Inuit on hunting expeditions.
Dan Cruickshank with his igloo
What's more certain, although perhaps surprising, is that the humble igloo has a lot to teach the modern British house-builder. Last year, a report by the government's architecture watchdog, Cabe, found more than four in five new homes built in Britain since 2002 failed to meet the needs of those who came to live in them.
By contrast, the design and construction principles enshrined by the igloo are enduring and are a response to the essential reasons people build - to create shelter from the elements and protection from danger.
Yet the way the igloo achieves these basic aims is ingenious and raises it from a mere utilitarian structure to a piece of architecture. It is not just a highly functional habitation but also a creation of elemental beauty that's an intensely pleasing and perfect expression of its function and manner and means of construction.
The igloo utilises what must be the potentially weakest of building materials - frozen water - and gives this unlikely structural material immense strength. Its domed form is not only a beautiful, and in many cultures a sacred form representing the heavens and Divine creation, but also a shape that is immensely strong.
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Dan Cruickshank's Adventures In Architecture is on BBC Two on Wednesdays at 2100 BST from 2 April
Frozen water - snow and ice - also have other striking qualities. It's the only readily cheap and available building material in much of the Arctic and is, of course, an utterly renewable resource. It's a construction material that causes no pollution whatsoever in its manufacture, use or disposal.
This paradoxical material - weak in its nature yet capable of great strength when used with intelligence - is the product of low temperature but an incomparable insulator, so that an igloo excludes external cold while retaining all the internal heat that is generated. Consequently, an igloo can resist the onslaught of the most fierce freezing gale, while its interior can be rapidly warmed by nothing more than body heat and the flame of a blubber lamp.
Ice has it
I landed at a tiny airport and made my way, across frozen fjords and pack ice, to the Inuit town of Ittoqqortoormiit to meet Andreas Sanimuinaq, who would teach me how to build an igloo; how its dome can be constructed with nothing more than a saw and without any need for props or supports during the construction process.
Andreas Sanimuinaq, master of a dying art
We boarded a sleigh and went in search of the correct, wind-compacted snow needed for igloo construction. Soon we found the right place. Andreas stamped out a circle in the snow - the plan of the igloo - sung a song to dedicate the circular structure we were about to build to the life-giving sun, and we got to work.
First we quarried blocks of snow - heavy brutes - and then carried them a few meters to the construction site, located on the snow-covered ice of the frozen fjord. The first three courses were laid, block on block with sides nearly vertical. The igloo is not a perfect hemispherical dome but more of an egg shape - in section a catenary arch - which is about the strongest form in nature. Halfway through the fourth course Andreas cut a wedge-shape block. This was the key structural moment.
From here the blocks rose upwards in a continuous spiral - a far stronger construction technique than placing course upon course that allowed the dome during construction to be self-supporting. I also discovered, as we worked, that blocks are held not so much by their tailored form as by friction and freezing. Surfaces that are to be joined are rubbed with the ice saw, the ice melts through the heat of friction and the blocks are rammed and held together while the surface moisture freezes, with the ice acting as mortar.
When we eventually completed the igloo I was able to enjoy the simple but effective science of the design. Hot air rises while cold air sinks, so as cold air lurked in the lower portion of the interior the warm air - created by our body heat - rose into the dome where it was trapped. We basked in this pleasant warmth while sitting on the high snow-block and skin-covered interior bench. The igloo is indeed a clever machine in which to live, for heat is balanced delicately against cold - it's a structure in which nature is harnessed to tame nature.
As water, caused by our body heat, trickled down the interior surface of the igloo, it completely filled the joints between blocks to refreeze during the cold of the night to form a grout between slabs that excludes all draughts. This constant thawing and refreezing rapidly transforms the igloo from a house of snow into a far stronger and windproof dwelling of solid ice.
But Andreas tells me that igloo construction is a dying art. The loss of the igloo is partly to do with changing culture - younger Inuit prefer to live in timber houses flown in from Denmark, and have little interest in learning the mystery of igloo construction.
Slotting ice blocks together
But perhaps more alarmingly, the demise of the igloo is to do with climate change. The area within the Arctic circle is now one of the most rapidly warming places on the planet. Here temperatures are rising nearly twice as fast as for the rest of the Earth and the permanent sea-ice cover has declined by almost 40% in the past 30 years.
This means that building igloos in the areas where the Inuit live and hunt is becoming increasingly difficult. Snow of the right consistency is harder to find and it is ever more difficult to freeze blocks together. The igloo has many lessons to teach, but tragically it seems that it may not be around much longer to teach them.