Energy consumption sometimes increases after a building has been refurbished. The reason for this is human psychology. However, there are ways of avoiding such pitfalls from energy efficiency measures so that no rebound effect occurs.
Higher consumption instead of increased efficiency
Owners expect clear savings of energy and heating costs as well as an increase in energy efficiency from energy-efficient refurbishment. But sometimes the construction work makes hardly any difference to their purses or energy consumption even increases. How can that be? Experts call this phenomenon the rebound or boomerang effect.
This effect is psychological in nature and works as follows: after extensive and often expensive refurbishment, residents think that they have already done enough now and no longer need to worry so much about saving energy and consuming resources. This means that residents tend to turn the heating up instead of simply putting on a pullover. They simply treat themselves to a few degrees more in the living room than before the refurbishment. Or underfloor heating is installed in those rooms which tend to be used less but this heating is left on simply because it is now there. Such behaviour cancels out any efficiency gains, which is of course then quickly reflected in the heating cost bill.
Another variation of the rebound effect is explained by a lack of trust in technology. Passive homes, for example, are designed so that moisture and CO2 in the air are extracted by a built-in ventilation system. There is more or less no need to let in fresh air by opening the windows. Nevertheless, residents occasionally leave the windows open for a long time because they have the feeling that this is how to get fresh air into the place.
The best behaviour for saving energy
The Heat Monitor , which was published by the German Institute for Economic Research (DIW Berlin) on the basis of data from the energy service provider, ista Deutschland GmbH, clearly shows how important user behaviour is when it comes to saving energy. Although a relatively high number of buildings in Germany have been refurbished to become energy-efficient, private households have consumed more heating energy than the year before. The fact that, on average, they nevertheless managed to save money was therefore not due to energy-efficient consumption behaviour but to the current low gas and oil prices.
The following therefore applies all the more: the greater residents’ energy awareness is, the more they themselves can contribute towards saving energy and reducing CO2 emissions. On average, 85% of the energy a household consumes goes on heating. Even small changes in user behaviour can make a significant contribution to climate protection. Very simple measures are, for example, opening windows regularly but briefly instead of leaving them permanently on tilt, lowering the heating temperature at night and when nobody is at home, bleeding the radiators regularly or sealing draughty windows.
Recording energy consumption
Even in an energy-efficient building, energy-conscious behaviour is therefore important to achieve optimum results. One way of preventing an unwanted increase in consumption is to record energy consumption precisely using metering devices in order to detect any changes in behaviour. Nowadays, there are numerous smart phone apps, such as the Energy Consumption Analyzer – naturally, you can also record and analyse your consumption simply and free of charge in an Excel file. So at the end of the month, you can get a good feeling for how much energy has been used and, if necessary, look for causes of any increase.
Consider component life-cycle assessment
Another pitfall from energy efficiency measures is to view the operating phase of buildings in isolation. Although the Energy Conservation Regulations (EnEV; link only German) regulate the heat insulation and energy-saving systems engineering in buildings, experts believe that this is not enough to achieve efficient climate protection – because the regulations take too narrow a view. In a typical new build, heating and hot water account for roughly one third of emissions and the electricity required for electrical appliances and lighting for another third. The remaining emissions are caused by construction and the disposal of components. However, so far the building and demolition phases have been more or less disregarded.
In addition to as low an energy requirement of the building as possible, “ecological building” also means using sustainable building materials which can be produced, used and disposed of with little impact on resources.
Take polystyrene as an example: this affordable material is frequently used for heat insulation. At first glance, that appears to be good for the developer because it reduces heating costs. However, the production of polystyrene involves high energy consumption. As the sheets often contain flame retardants, they have to be disposed of as hazardous waste. That is expensive and anything but environmentally friendly. More ecological alternatives which provide the same insulation would be, for example, insulation materials made of cellulose, hemp, sheep’s wool, cork or recycled newspapers.
It is mainly in the hands of the property developers to have a major impact on the energy footprint of their buildings. Anyone who wants to know how you can completely optimise a home with little impact on your wallet and the environment should request a life-cycle analysis of the new build and refurbishment measures from architects and planners.