Is not impossible. It’s not likely either.

Insulation pays back over a long enough time horizon (economically or CO2 wise). Although spray foam at the moment does have a large CO2 impact. If someone is putting in way too much insulation then we could say that the last 30% of insulation wasn't worth it. When people say something won't payback economically on a home, they are usually looking at a time frame of 10 years or less.

In this case the insulation itself will probably payback quickly. The problem is the cost of re-siding the house to get the insulation in- likely similar for CO2 impact.

That’s very unlikely. Insulation lasts decades and is not that difficult to produce.

It is possible. You can't measure that in currency, though.

If there was a carbon tax you might be able too.

I absolutely agree this kind of nontrivial work can be done in a way that is woefully inefficient/impractical. My EWI, approx 85m2 of graphite polystyrene with an embedded CO2[1] of ~15kg/m2 is equivalent to approximately 1.5 years of CO2 emissions (combined electricity & gas), or ~9 months of CO2 emissions before I replaced windows and old kerosene boiler that came with the house.

Actual installation and other materials excluded (adhesives, mesh, silicone render, 450 hot beverages, getting the neighbour's car repaired after the scaffolders hit it, etc.) excluded.

I don't have a full year of data yet, but all in it's looking like CO2 emissions are going to come in at well under 40%. This is in line with the independent assessment I needed to clear a grant for some of the costs[2]. It seems to me "carbon ROI" is about 1/4 the financial ROI (est 8+ years).

Now if it was PU instead of EPS that would be a different cost (10x the CO2 of polystyrene). Sadly I also ended up with some PU (PIR) in a small area of low-pitched roof void, I don't know if there were better choices there.

There's also a hidden cost in living in a cold, damp building - now there are winter days when I don't even turn the heat on at all.

[1] https://www.greenspec.co.uk/building-design/embodied-carbon-... [2] https://www.seai.ie/publications/Your-Guide-to-Building-Ener...