黑洞社区

The theories of a 19th century economist might seem a little out of touch for 21st century sustainability pioneers, but William Stanley Jevons is throwing up some awkward questions about energy efficient buildings.

The Jevons paradox, also known as the rebound effect, states that greater efficiency leads to cheaper fuel, which encourages fuel consumption. New research by Dr Terry Barker of Cambridge University has confirmed that energy efficiency is a double-edged sword.

Barker predicts that by 2030, half the CO2 savings gained from the development of fuel-efficient transport, buildings and industry will be cancelled out by a rise in the global consumption of fossil fuels. He believes this rebound effect has been ignored by policymakers, who see improvements in energy efficiency as a pain-free way to tackle climate change.

鈥淕overnments have to take account of the fact that half the effects of energy efficiency policies could be lost,鈥� says Barker, director of the Cambridge Centre for Climate Change Mitigation Research.

The coal question

黑洞社区 Regulations are being progressively tightened in the UK and last month Steven Chu, the US energy secretary, talked of making commercial buildings 80% more energy efficient. But Barker says the rebound effect means that 鈥渆fficiency programmes have to be ramped up to achieve the same targets鈥�.

Jevons presented the eponymous paradox in his 1865 book The Coal Question. He observed that England consumed much more coal after James Watt made fuel-efficiency improvements to Thomas Newcomen鈥檚 steam engine. Barker is using Jevons鈥� principle to attempt a forecast of the global effects of modern efficiency policies.

The theory is that businesses which save money on fuel will pass the savings on to customers in the form of lower prices for goods or services. The price cuts stimulate sales, meaning more production, which means more fuel consumption.

Driving force

On a personal level, the owner of a car that does more miles to the gallon is likely to use it more frequently or spend the money saved on other manufactured products, such as a bigger car or a holiday abroad. There is evidence that homeowners tend to use their heating more after making their homes better insulated.

The owner of a car that does more miles to the gallon is likely to use it more frequently or spend the money saved on other manufactured products

Barker says that about 75% of the global rebound effect will take place in developing countries, as the relative fall in fossil fuel prices that arises from greater efficiency makes the fuels accessible to more businesses and individuals. But it will be felt significantly in developed countries. An earlier study by Barker on the effects of energy efficiency policies in the UK between 2000 and 2010 calculated a rebound effect of 26%.

Barker says that in the case of commercial buildings, 鈥渨hat would have been spent on heating will get spent on something else, and that 鈥榮omething else鈥� can be carbon-intensive. For example, if the tenant offers legal services, we would expect them to reduce their charges and expand a bit. It would be a small effect, but it鈥檚 not zero.鈥�

Retailers such as Tesco and Marks & Spencer, which are making strenuous efforts to cut carbon emissions from their buildings, should also be aware of the rebound effect. 鈥淭hey would save on energy, but it would mean they make more profit or reduce their prices, which means more Tesco stores,鈥� says Barker. 鈥淚t would be wrong to count the immediate carbon saving [from a better building] and say that鈥檚 it. You have to look at the inter-connectedness of the economy. If you have an energy efficiency drive, it will cut your emissions, but not by as much as it appears at first sight because of the indirect effects.鈥�

Barker, a co-author of the third and fourth reports by the Intergovernmental Panel on Climate Change, believes that efficiency policies must be accompanied by measures to keep fossil fuel prices high, possibly through higher taxes or cap-and-trade schemes. This would limit the rebound and encourage a move to low/zero carbon fuels, such as solar and wind.

Keep building green

He insists that the construction industry should continue its efforts to reduce fuel consumption in buildings: 鈥淭he macro-economic effects of energy efficiency are the government鈥檚 responsibility. Architects and engineers need to move ahead to zero-carbon buildings as fast as possible.鈥�

Barker鈥檚 conclusions are supported by Steven Sorrell, a senior fellow at Sussex University. He published a review of research into the rebound effect earlier this year, which found that on average 20% of the energy savings gained by better home insulation are lost because the occupiers use the heating more. The losses could rise to 50% in low-income households.

Sorrell says there needs to be more research: 鈥淭his area has been seriously neglected. It is difficult to quantify, but that鈥檚 not a reason not to study it. Perhaps the implications are rather uncomfortable.鈥�

George Stowell, an architect and a member of RIBA鈥檚 Sustainable Futures Group, believes the most effective action his clients can take is to buy low-carbon electricity. Like Sutton, he wants more research to assess the true levels of the rebound effect in buildings. 鈥淚f you reduce the cost of comfort [in a building], occupiers will have the thermostat set higher in winter or the air-conditioning set lower in summer, and they鈥檒l use more energy. That鈥檚 the theory, but the detailed research hasn't been done yet.鈥�

The Department of Energy and Climate Change said: 鈥淭he rebound effect has been factored into our existing policies on energy efficiency. But there is no such thing as a low-cost, high-carbon future, which is why we are cleaning up our energy supplies with more renewables, clean coal and nuclear power. Saving energy is just the start, and is one of the simplest, most affordable ways to combat climate change and prevent fuel poverty.鈥�