I came across
this little ruby while I was wandering about on the web.
Although it's intended audience is European, and the examples are aimed at that audience, there are some great ideas here. It would be very useful if the above chart could be adapted to N. America.
But even so, it is very interesting the difference that an 80% Heat Recovery Ventillator makes in wall thickness vs. a 60% HRV.
-AC_Hacker