COLUMN BUILDING SCIENCES not have to be rigid with this approach-windows being "innies" with the water control layer and air control layer being the structural sheathing. The continuous insulation does not have to be extruded polystyrene (XPS) or expanded polystyrene (EPS) or foil faced isocyanurate. It could be mineral fiber insulation boards (aka "stone wool"). See Figure 4. It can be any type of continuous insulation: rigid or mineral fiber. And you can make the continuous insulation pretty much any thickness. Check out Photo 1. The trim is returned to the flange or face of the inset window. The flashing at the top of the window opening at the horizontal strip of head trim just covers the top of the trim itself-it only protects the top of the trim-it does not have to extend to the back of the continuous insulation and connect to the face of the structural sheathing/water control and air control layer. The window head-the flange at the top of the window-is already flashed to the face of the structural sheathing/water control and air control layer behind the continuous insulation. A gap is left at the inboard side of the horizontal return trim at the top of the window opening to let any penetrating rainwater run out between the window flange and the horizontal trim (Figure 5). Now let's go with "outies" with the water and air control layer being the face of the continuous insulation. Check out the sequence of installation (Figure 6). We have seen this before. We have been doing this for over 50 years. Note that the water control of the flanged window lines FIGURE 3 Window Installation Sequence for "Innies." The water and air control layer is the sheathing behind the continuous insulation. Note that the water control of the flanged window lines up with the water control of the sheathing. Note the sloping sill. Note that the pan flashing can be liquid applied or a formable membrane. Note that sealant is not necessary (or desirable) behind the window flanges. Note that the seams in the continuous insulation do not need to be sealed or taped. A B C D E A) Structural sheathing installed over frame wall; B) Install beveled wood siding in frame opening at sill to create slope; C) Install formable flashing at sill; D) Install window plumb, level and square; E) Install flashing tape at jambs. F G H I J F) Install flashing tape at head; G) Install continuous insulation; H) Interior view prior to window installation; I) Interior view after window installation; J) Air seal window around entire perimeter with sealant and sealant backer rod. 58 ASHRAE JOURNAL ashrae.org APRI L 2015