[Gibbon1]

> Counter-intuitively, air sealing is usually the #1 improvement.

I think the hard thing for people to think about is that heat transfer is exponential. But we don't measure it that way. In fact R values are really misleading[1].

Meaning transfer coefficients can vary by orders of magnitude. So it's easy for one source like air leakage to totally swamp every other source.

[1] Figure of merit is really 1/R (smaller is better) not R.