In the good old days, when fuel was cheap and carpenters were simple, no one cared a whit about insulation and — God forbid! — energy performance.  But now that we’re out of Eden, we need to concern ourselves with more than roof framing and perfectly coped crown.  Thermal performance, rain screens, and indoor air quality are now firmly in the carpenter’s bailiwick, but can be much more abstract than a tight-fitting miter joint.  That’s why I’m always looking for instances where building science reveals itself in glorious, explicit detail.   On a recent morning, I noticed this stripey pattern in the dew on my roof.   (Ignore the leaning chimney — it’s an experiment in non-Euclidean masonry)  Years ago I might have though,…