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# I expected altering the level of insulation to make a bigger difference

The difference in greenhouse gas emissions from the all at level 1 pathway[1] and a pathway whose only difference is level 4 effort on insulation[2] is only 3% of 1990 levels. This may appear smaller than expected.

You can follow the calculations in the underlying excel model. Below is an explanation and cross-check against UK emissions statistics.

It is worth noting that the calculator does not capture the full benefit of insulation. In particular, insulation may have a significant impact on the need to provide 'peaking' electricity.

Of 2009’s 562 Mt CO2e total emissions of all GHGs, 213 Mt CO2e (38%) can be attributed to buildings, of which 143.2 Mt CO2e (25%) is from domestic buildings.

85.2 Mt CO2e (15.2%) can be attributed to space heating of buildings, of which 64.4 Mt CO2e (11.5%) is from space heating of domestic buildings.

By 2050 the building stock will have grown somewhat, and the fuel-mix for electricity is under the user’s control, so these numbers should not be expected to match perfectly.

The “home insulation” lever allows, at level 1 (business as usual), for the average leakiness of a home to decrease by 25%, and, at level 4, for the leakiness to decrease by 50%. Based on the above numbers, one might expect the effect of this lever on emissions to be very roughly (50%-25%)x 64.4 Mt CO2e = 16.1 Mt, or (50%-25%)x11.5% = 2.86%.

Here’s what the calculator says. Starting from the all-level-1 pathway, emissions in 2050 are 752 Mt. When the “home insulation” lever is cranked up to level 4, emissions decrease to 728 Mt, a decrease of 24 Mt (3.2%).

If we attempt to emulate today’s conditions by taking the all-level-1 pathway but setting “average temperature of homes” to level 2 (temperatures slightly above today) or 3 (temperatures slightly below today), then the decrease resulting from swinging the “home insulation” lever from 1 to 4 changes to 18 Mt (2.5%) or 16 Mt (2.3%) respectively.