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The problem of the rebound effect that cancels the benefits of thermal insulation

The research was conducted on a sample of 55 thousand homes between Wales and England

(sustainabilityenvironment.com) – The thermal insulation of the floors and cavities of houses reduces the consumption of gas for heating only for the first two years. Then the retrofit is canceled bringing with it also the energy saving. This is not a new scoop, but a study by the University of Cambrige on housing in England and Wales, which, for the first time, details what happens to gas consumption before and after a retrofit operation, based, however, solely on increased insulation of the casing.

Within four years the benefits will zero

The researchers analyzed the consumption of more than 55,000 homes in twelve years (2005-2017) and found that the thermal insulation of the cavities led to an average drop in consumption of 7% during the first year. These benefits were reduced to 2.7% in the second year, reaching the fourth year to be even negligible. The same applies to the insulation of the roofs which, if possible, had a further reduced effect. The team identified these behaviors with the “rebound effect” label, a term coined back in the 1800s when it was observed that more efficient steam engines increased rather than reduced the use of coal, as engines were used more widely.

“Any savings made through energy efficiency are offset by a steady increase in energy consumption,” the research points out.

But because this happens, higher efficiency should mean lower energy requirements and consequently savings.

For the researchers behind the study, published in the journal Energy Economics, the answer is not unique, but could find an explanation in changing the behaviors of households that benefit from these energy retrofits.

The work of increasing the efficiency of the outer shell (walls, roofing, windows, cavities) in England and Wales are almost always accompanied by the expansion of the houses. Additions of conservatories, typical in this region, new premises for domestic use and not only. Extra rooms to heat or cool. In addition, a hermetic house implies a greater air exchange and open windows contribute to significantly changing the interior comfort, thereby increasing consumption.

Thermal insulation alone is not enough

This is why the researchers stress that every thermal insulation intervention must always be accompanied by combined investments, for example for the installation of heat pumps and for raising awareness of different behaviors.

This study does not say that energy efficiency does not work,said Professor Laura Diaz Anadon, director of the Cambridge Center for Environment, Energy and Natural Resource Governance and co-author of the study. “However, home isolation alone is not a magic bullet“. Research has obviously focused on the UK market where residential housing accounted for almost a third (29.5%) of the country’s total energy consumption in 2020, according to the International Energy Agency. But it could easily be extended to other similar countries. According to the IEA, around 177,000 heat pumps were installed globally in 2020. To reach the zero-emissions scenario, by 2030 we should reach at least 600,000 units, but the current trend leads us to just over 253 thousand installations.

Not encouraging homeowners to “fully degasify heating” while going through the disruption of a retrofit is a missed opportunity“.

Current increases in the cost of gas compared to when research was conducted are in fact further confirmation of the suggestions put forward by the researchers.

Despite our antiquated and dated heritage, we Italians are on the right track from this point of view. The GBC Italy, one of the most representative bodies internationally in the field of green building, states that the Italy can already boast 18.6 million square meters of efficient buildings, less polluting and capable of producing significant savings in terms of costs and emissions.

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