By Nick Triggle BBC News Online

With temperatures poised to reach 30C by Tuesday and humidity levels set to soar, the forecast for the next few days could well be one of sweaty workmates and clammy families.

During last year's record-busting heat wave it hit 37.7C (100F) for the first time and many people expect British summers to keep getting hotter.

When temperatures rise we can now move from one carefully controlled environment to another - with air conditioning in large offices, shops and new cars commonplace.

Such systems are still a rarity in UK homes, but could that all be about to change, with householders following the example of their US and European counterparts in the battle against summer heat?

DIY-loving

At present domestic units account for just a fraction of the £500m air conditioning market in the UK.

It is estimated that air conditioning systems, not including portable units, are fitted in just 7,500 homes.

But suppliers say demand is increasing along with temperatures, as DIY-loving homeowners investigate ways to make their houses comfortable all year round.

John Ray, 69, from London, is one of a number of people who decided enough was enough last summer.

Keeping cool in summer has long been a problem

He spent £1,400 having an air conditioner fitted in his bedroom, which doubles as an office.

"The room got so hot last year, but as my flat overlooks a busy road I can't open the windows.

"The worst thing was not being able to sleep at night, I just had to do something. I switched it on during the hot week we had in June and it was great."

Andrew Cohen, managing director of The Air Conditioning Company, which supplied Mr Ray's system, says more and more people are going to turn to air conditioning to beat the heat.

His company specialises in small systems and he estimates 50% of its sales are to home-owners.

"There is a tremendous market for domestic air conditioners. Last summer they were phoning up left, right and centre," he says.

"People are now taking air conditioning for granted. Many people have it in cars and at work and no longer see it as a luxury."

Portable units

In the US, air conditioning has been fitted in homes ever since Willis Carrier invented the "weather-maker" in 1928.

As more energy is used, the climate warms and, then, demand for air conditioners goes up Friends of the Earth

In Britain they have tended to remain the preserve of the rich, but the industry hopes all that with change, particularly with the arrival of cheaper units.

Basic portable air conditioners can now be picked up for around £80, with more powerful units costing from £200 upwards.

But portable units are unpopular with many users, as they are noisy and simply push warm air into another room - which will quickly heat up.

Fixed systems, similar to those found in small offices, can also be used in the home.

A wall-mounted unit that will cool one room can be bought for £1,000 but installation can cost almost as much again. To install a system to air condition a whole house would cost in the region of £4,500.

'Heat demand'

While making life that little bit more comfortable for those who have them, it is not just their price that puts people off.

Friends of the Earth energy campaigner Bryony Worthington says: "The problem with air conditioners is the heat demand they create.

"As more energy is used, the climate warms and, then, demand for air conditioners goes up. It is a vicious cycle.

In Tokyo, where air conditioners are common, warm air pushed out from homes and offices heats up the city, making already high temperatures even more uncomfortable.

Japanese prime minister, Junichiro Koizumi said: "I am not a fan of air conditioners, but I'm finding it difficult to sleep without one at the moment," as temperatures hit a record 39.5C (103F), in July.

'Energy-efficient'

Despite such problems, the air conditioning industry is confident that new technology could help sell more domestic units.

Heat pumps are seen as one way forward, because they use far less power than conventional air conditioning systems by taking three-quarters of the heat they supply from the ground.

Air conditioners have added to summer heat in Tokyo

Around 90% of the models available have the ability to reverse the cycle or, in layman terms, to cool buildings - making them a realistic alternative to air conditioners.

Terry Seward, of the Federation of Environmental Trade Associations, which represents air conditioning firms, says: "Heat pumps will be used more and more in the future, the government is keen on them as they are incredibly energy-efficient."

Several housing associations have already started using them in new developments instead of traditional central heating systems, says Mr Seward.

"They cost between £5,000 and £8,000 to fit in the average house so they are more expensive than a traditional boiler system but in the long-term savings can be made."

Shading

Heat pumps have also proved popular with the green lobby, because they release far less greenhouse gases.

"Heat pumps are good and so are solar-powered air conditioners," says Friends of the Earth.

But it remains unconvinced that even they are the right way forward in a country which never really gets all that hot.