Vented Roof All Structure Inside; Okay, Not The Trusses But You Know What I Mean Ventilated Cladding Thermal Control Layer Outside of Air and Vapor Control Layers Continuous Air Control and Vapor Control Layer Outside of Structure Ventilated Cladding All Services Inside; All, Not Some, All and I Really Mean It Figure 1: simplest design solution. The bold line represents the air control and vapor control layers. The shaded layer represents the thermal control layer. The dotted line represents a ventilated cladding. The roof is a vented attic. Classic simple stuff. Any bad stuff from inside that gets past the bold line and gets into the shaded stuff can pass right on through and get to the outside through the dotted line and the big sloped hat with the holes. Here is the secret—the control layers need to be continuous— especially the air control layer. If you don’t have air moving across your wall or roof assembly, not much bad can or does happen. Check out Figure 1 for a conceptual description of the simplest design solution. The bold line represents the air control and vapor control layers. The shaded layer represents www.info.hotims.com/37990-69 September 2011 ASHRAE Journal 65