People who design insulation systems start with the "typical details"—cross sections through uninterrupted walls. This is pretty silly, since in most houses insulation problems occur at places where materials change or the building turns a corner. One particularly vexing place where insulation systems break down is the intersection of roof and wall. I have written in another column on the visual importance of the exterior roof-wall intersection. What goes on inside is equally important and often influences the exterior appearance. In fact, solving the insulation details may lead you to better exterior eaves details. Eaves at Unoccupied Attic Floors In the typical one- or two-story house with an occupied attic, the eaves are at the same level as the floor (see Figure