The phenomenon of the rebound effect - is the efficiency of green homes at risk because of inhabitants’ behaviour?

Appliances can be the pitfall for potential home energy savings. In theory, energy efficient appliances should help towards the target for zero carbon housing. But in reality, while energy efficient appliances are now readily available to consumers, their decreasing cost means that consumers are buying more and using them more.


As we discussed in our recent blog post, energy efficient appliances do not automatically equate to reduced energy use. This is very much dependent on cultural norms, which have evolved and changed to be contrary to energy efficiency associated with zero carbon homes.





Developing zero carbon homes could be harder as appliance use increases

This is particularly true of mainstream electrical goods, where falling prices and lifestyle changes mean that families often run multiple television sets, music systems or games consoles at the same time in different rooms in their home. Without properly addressing appliance usage zero carbon design can be rendered ineffective.

Societal barriers to zero carbon homes

As we explain in the forth chapter of our  report, How occupants behave and interact with their homes, this is all part of the phenomenon known as the rebound effect – the reduction of the potential energy savings caused by the user of an appliance offsetting some of the savings through changed behaviour. Common examples include justifying leaving lights on for longer, because the bulbs are energy efficient, or heating the house to a higher temperature after insulating the walls and loft.

This theory was originally put forward by economist William Jevons, who said that as energy efficiency increases, energy consuming products become less expensive to run, which ultimately means people consume more energy. Potentially, this will stand to be a substantial obstacle in achieving the Government’s zero carbon homes targets in the UK.

The theory has been subject to debate by commentators on energy efficiency globally (have a look here, here and here). In a blog post he wrote back in January, Real Climate Economics blogger James Barrett examined the truth behind the rebound effect concluding that, while the theory can be proved, vitally it does not make energy efficiency efforts a waste of time.

It is important that this message resonates with consumers. In the face of research, such as the UK Energy Research Centre’s report on home energy use, which suggests that the rebound effect will have a serious negative impact on creating sustainable homes in the UK, consumers need to be engaged with the concept of leading sustainable lives.

The National Geographic has sought to do this with the Great Energy Challenge. As part of this holistic project to get consumers thinking about their energy use and its wider impact, they launched the 360 degrees Energy Diet, which saw families around the world change their lifestyles to reduce energy consumption and share their experiences online.

While this particular project has encouraged consumers to make their homes more sustainable, in order to truly combat the rebound effect a sound understanding of what motivates people to reduce their energy consumption is required. The rebound theory certainly makes it clear that behavioural and societal norms are proving to be a barrier to creating sustainable housing. The WBSCD has identified barriers to individuals becoming energy efficient as:

• the desire to be comfortable

• a belief that their small effort won’t make a difference on a larger scale

• the argument that they cannot afford to make changes to their lives

• that it is simply too much effort

We feel that more research into consumer perceptions of energy efficiency and sustainable homes is needed in order to understand how energy efficiency can truly be achieved. NHBC Foundation is currently embarking on consumer research which will look into this, and wider issues affecting zero carbon homes.

The results of this research will be released in the coming months – but in the meantime, we welcome any comments or thoughts you may have on this topic.

Advancing the zero carbon agenda

Zero Carbon Compendium 2011: who’s doing what in housing worldwide

This week the NHBC Foundation, in partnership with Zero Carbon Hub and PRP Architects, published an extensively updated version of the Zero Carbon Compendium - the international comparison illustrating how different countries are tackling greenhouse gas emission reductions in their residential sectors. The 2011 Compendium enhances the previous edition and includes five new countries – Brazil, India, Russia, Singapore and South Africa – giving a wider international picture of the endeavour to achieve low carbon housing.

Targets, exemplar projects and policies have also been updated to provide an accurate snapshot of the global situation. All the countries featured in the Compendium have different targets for reducing their carbon emissions, as well as ways of achieving those reductions - differences that are largely governed by country-specific factors, like climate, availability of energy resources, social and political background. Most of the countries studied are united by a commitment to the global Kyoto protocol which came into force in 2005 and dictates that all member states reduce their collective greenhouse gas emissions by 5.2% from the 1990 level by 2012.

The latest edition of the Compendium explores each country, looking at its carbon reduction starting position, its unique energy needs and its energy-saving aspirations.

Key lessons identified in the Zero Carbon Compendium:

1) All countries are experiencing change, whether this is economic, social or political, which has a consequent impact on the direction and extent of carbon reduction strategies. Energy efficiency in housing is now widely recognised as vital, with Germany - an early initiator - evolving it’s low energy building programme rapidly. In addition, Germany’s stringent Energy Conservation Regulations, revised in 2009, commits to meeting 15% of heating, hot water or cooling energy demand using renewables. The housing regulations in the Scandinavian nations of Denmark and Sweden are also considered world leading examples of efforts to reduce carbon emissions of housing stock.

2) Targets should be reviewed regularly to maintain effectiveness. This is already the case in China which has implemented an Energy Development Plan, reviewed every five years, to reduce energy consumption of public and residential buildings by 65% by 2020.

3) A shortage of adequate housing remains a considerable challenge to achieving zero carbon targets. This applies particularly in countries such as South Africa and Brazil which have the greater shortfalls in housing and where quality (in sustainability terms) is in danger of being perceived to be less urgent than the need for quantity.

4) Energy supply mix is an important factor when considering national energy efficiency. The Compendium reveals the variation in the extent to which different renewable energy sources contribute to overall energy supply in each country (see image below, click on image for larger version). In the residential sector, just 4% of energy in the Netherlands comes from non-fossil fuels, while in New Zealand this total is more than 60%, largely through hydro power.

5) Green Building Councils and green rating schemes are proliferating globally, marking a commitment to improve housing standards and to progress the zero carbon homes agenda. Among the rating schemes, the Green Star system in Australia, adapted to suit the country’s climate from the UK’s BREEAM and US LEED schemes is a notable success. Green Star has since been adopted in New Zealand and South Africa. Development of aspirational standards has paved the way for many countries to put in place more stringent national requirements for new housing.

6) Solid research and understanding of a country’s housing energy needs is important in developing an appropriate strategy for low carbon housing. The chart below (click on chart for larger version) highlights the diversity of consumer energy use in each country. Brazil makes for an interesting study: appliance and lighting makes up a large proportion of energy use in Brazil’s housing. To reduce electricity consumption and to increase the proportion of energy produced by renewable sources, Brazil has implemented appliance labelling schemes and tax subsidies for owners of properties that use solar energy.


7) Each country should strike a balance between encouraging the widest possible uptake of existing technology while supporting new, promising technologies that are appropriate for the local situation. A notable conclusion is that small, relatively low cost, changes in approach and practice, if accepted and applied widely, can have significant impact. Such changes may be related, for example, to improved installation, better controls, better advice and passive measures.