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.
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.