Our homes are necessary to us for many reasons, but the most basic of these is as shelter from the unwanted aspects of climate. Climate can vary greatly from season to season, and from place to place, which is why building forms and material choices vary so greatly across the globe.
The availability of building materials will suggest a vernacular to an extent, although exactly which materials were chosen, historically at least, were also largely climate driven. Old building designs evolved over very long time scales on the principle of survival of the fittest, and those that have passed the test of time are those that are best able to modify their local external climate to create the most comfortable internal space.
Clearly keeping the rain (or sun) off would have been the initial ambition of our un-housed ancestors, but after that making a shelter comfortable came down to controlling temperature, be it warming or cooling, and there are many different techniques to ensure the right temperature, depending upon your location/situation.
In the tropics it is hot and humid; in the Saharan desert it is dry and hot by day, cold by night; it is also very dry towards the poles, but very cold; and in the temperate zones it can more or less display all of these combinations to lesser extremes.
Any building may be heated or cooled by devices that require energy – however many styles of ancient buildings developed to moderate their internal climates passively, either because the technology wasn’t available to do it otherwise, or because energy was scarce and expensive.
In hot, humid places, buildings evolved to be lightweight so as not to store heat, and porous to encourage airflow, with large overhangs to shield the sun.
In hot arid places, buildings packed closely together and evolved to be heavyweight to soak up the daytime heat and let it out into the cool night, with small openings used to ventilate at night.
In cold arid places buildings evolved as squat wind shelters, with south facing openings and insulation to keep the heat in.
In northern Europe, our climate can regularly vary anywhere between -10°C and 30°C, is predominately humid/wet but with potential dry spells, and subject to windy conditions, and our buildings have evolved to be able to cope reasonably well with all eventualities - without excelling at any. Whilst largely all being able to remain as cool as necessary, we do rely on energy for heating, and the humble fire has evolved to consume that which has until more recently been considered cheap and plentiful.
Energy is once again becoming scarce and expensive however, and what is more, its profligate use is changing the very climates in which we have evolved. Ideally, in order to create a comfortable internal climate we must try and moderate our external climate using as little energy as we can - as did our forebears.