Allison Bailes, the inimitable and ever-engaging mind behind the Energy Vanguard blog, is a physicist. Behind his smile and down-to-earth demeanor is a guy that loves math and is not afraid to admit it.
In a not-very-recent post, he provides this warning: "This section contains mathematics. If you feel nausea or dizziness, skip to the conclusion below. If you feel excited by this discussion, see your local physics department. If your arousal lasts longer than 4 hours, you should work through the problems in Classical Electrodynamics by J.D. Jackson." His post, "Flat or Lumpy - How would You Like Your Insulation?," does contain some calculations, but they really aren't that bad. And they are essential to understanding why the energy performance of attic insulation can be improved simply by raking the insulation flat after electricians have wreaked havoc on it rewiring the house, or the cable guy has installed a new line.
The same calculations are used to evaluate the effect windows have on the energy performance of a wall system (see "Holes in the Wall: To Improve the Energy Performance of Walls, Look at Total R- Value," 2/14). The take-home message here is that a wall with windows will have significantly reduced R-value, and simply adding more insulation is not necessarily the best way to improve thermal performance.