Jean-Paul closed the front door with a sigh of relief. It was good to be home after a cold, damp day on the PyreneanThe Pyrenees are a range of mountains dividing Spain from France. farm. He would turn up the central heating, put his wet clothes on the radiator and stretch out his feet in front of the fire. But then, with a shock, he remembered: this was an ultra-modern house. There was no central heating, no radiator, no fire.

Sitting by the fire is so relaxing that it has been found to lower people's blood pressure. Psychologists attribute this to instincts rooted in the Stone AgeA prehistoric age in which stones were used as tools. It ended around 4,000BC, when metal began to be used instead., when our ancestors gathered round fires for company and protection against the harsh outside world.

Warmth is essential to human survival, but paradoxically is now endangering it. Using fossil fuels to heat our houses is a major cause of global warming and climate change.

In the UK, around 15% of greenhouse gases stem from domestic heating and hot water; in France, the figure is 20%. In Australia, with its warmer climate, households consume 10% of the country's total energy.

Various schemes for reducing these figures have been suggested. One is the replacement of gas boilers by heat pumps, which extract warmth from the air, ground or water, operating rather like fridges in reverse. In the USA, it has been estimated that replacing gas by heat pumps would reduce CO2 emissions by more than 75%.

But heat pumps cost much more than gas boilers: between £6,000 and £18,000, depending on the size of the house. Making them work efficiently also demands a high degree of insulation. So although the British government has just announced subsidies of £5,000 for switching to them, households still face a hefty bill.

For some, the answer lies not in making old houses more energy-efficient, but in building new ones that require little or no energy to heat them. One particularly exciting idea is the Passive HouseThe original German name is very similar: Passivhaus.. Developed by a German and a Swedish academicWolfgang Feist and Bo Adamson first came up with the idea in 1988., it makes as much use as possible of sunshine, shade and outside air to maintain a comfortable temperature, instead of central heating or air conditioning.

Passive Houses have what experts call "superinsulation". While ordinary houses possess weak spotsThese are referred to as "thermal bridging". which allow heat to escape, such as draughty windows, the new design aims to create an airtight "envelope" - using, among other things, triple glazing.

This means that very little heat can escape, so the house can be warmed mainly by the body heat of the people inside, and the heat produced by electrical appliances such as ovens and lights.

Passive Houses also have a heat-recovery ventilator (HRV) to take out stale air and bring in fresh. This extracts heat from the air going out and uses it to warm the air coming in.  

As for keeping cool in summer, a system of blinds and shutters is used to control the sunlight.

Some say, yes. Doing so would have a huge effect on lowering carbon emissions, and go a long way towards saving the planet. Passive Houses are clearly the way forward, so every new building should follow their principles. In the meantime, we can just put on warmer clothes when the temperature drops: it is a small sacrifice which is clearly worth making for such an important cause.

Others point out that most people simply do not have the money to buy state-of-the-art houses. They will have to go on living in old houses, which - however well insulated - will always need heating. Putting on another jumper will not save old people from dying of hypothermia. In any case, fires and heating provide psychological comfort which is essential to our wellbeing.