Insulation only temporarily lowers domestic gas use. The reduction in gas usage per household found in the first study to examine the long-term effects of home insulation in England and Wales was modest and only lasted a few years.

Insulating the lofts and cavity walls of existing UK housing stock barely reduces gas consumption for the first year, with all energy savings evaporating by the fourth year after a refit.

The study is the first to follow residential gas use in England and Wales in great detail before and after installing insulation for at least five years.

Researchers examined the gas usage trends of over 55,000 homes over twelve years (2005–2017), and they discovered that cavity wall insulation caused a 7% average reduction in gas consumption during the first year. By the second year, this dropped to 2.7%.

Loft insulation reduced gas usage on average by about 4% initially, 1.8% after one year, and insignificantly by the second year. This was half as effective as cavity wall insulation. Any improvements in energy efficiency for houses with conservatories* vanished after the first year.

According to the research, there may be a considerable “rebound effect” when it comes to residential insulation, whereby a gradual rise in energy consumption offsets any energy efficiency gains. With a strong focus on residential sector insulation retrofits, the UK Treasury recently announced the allocation of almost £6 billion in funds to cut the energy consumption of buildings.

Although it is very challenging to pinpoint particular sources of the “rebound effect” that their study, which was published in the journal Energy Economics, showed, actions like cranking up the heat, opening windows in stuffy rooms, or adding on to existing buildings may all contribute.

They contend that while effective insulation is essential, any effort to insulate UK homes should also include spending on heat pump installation and efforts to promote behaviour change if 2030 energy independence targets are to be realised.

To fully understand the impact of insulating homes, the researchers considered several variables, such as the age and size of buildings.

They did discover that the price of gas had an impact on energy use, so the current high price of gas may result in more significant energy savings through insulation than during the study period. The study also indicated that residential gas usage fluctuated less due to loft and cavity wall insulation. There are genuine benefits to households from good insulation, not least in health and comfort.

“Home insulation, however, is not a panacea. In the medium run, the rebound effect will be lessened by high gas prices since homeowners will be more cost-conscious. It may be less effective to fund more of the same insulation roll-out to achieve the UK’s carbon reduction and energy security ambitions. Heat pumps are highly efficient and eliminate the need for gas boilers by drawing heat from the outside to heat indoor radiators.”

“We observed that home renovations that increase consumption, like extensions, are frequently paired with energy efficiency retrofits.”

While the rest of the UK has decreased VAT in a tax rebate, Scotland currently offers grants and interest-free loans for heat pumps. According to the International Energy Agency, residential housing accounted for nearly a third (29.5%) of the UK’s energy consumption in 2020. 85% of households in the UK use gas as their primary heating source.

The study examined energy use in individual homes before and after insulation and between homes that underwent efficiency modifications and those that did not use data from the UK’s Department of Energy and Climate Change. Researchers discovered that homes in less affluent areas had half the reductions in gas use, or an average of 3% over the first and second years following insulation, compared to wealthier areas.

The least amount of gas usage reduction was observed in areas with the highest levels of deprivation.

According to Penasco, home insulation can readily be used to keep a house warmer for longer because households in less affluent areas frequently have to reduce their energy use. “This is a welcome result if measures are geared at decreasing fuel poverty in low-income homes, but it won’t assist with the UK’s emissions reduction ambitions or dependence on gas.” Those in the bottom 20% of household income increased their gas consumption after insulation.

Penasco asserts that setting individual household energy reduction goals and linking them to long-term waivers on energy bills, particularly for low-income households, would be preferable to national gas price ceilings to incentivise individuals to conserve energy.

“People do not purposefully waste energy savings,” Anadon continued. To reduce the reported rebound impact, education is necessary. Ministers’ media appearances to address boiler flow temperatures are encouraging indications that the government is beginning to give this some thought.