What is the proper depth of window and door placement in an ICF wall?
The proper depth of window and door placement in an ICF wall is one that aligns the glazing with the exterior layer of continuous insulation. This means that ideally, the pane of glass should be on the same plane as the exterior foam panel of the ICF block. With this approach, the rough openings may need to be lined with buck, depending on the thickness of the ICF insulation layer. The buck can either be wood sheathing, or a specialized accessory product like Logix’s Pro Buck.
The section detail below provides an illustration of this glazing-ICF interface:
Why Doors and Glazing Should Align With the Exterior ICF Insulation Panel
The reason for this alignment with the exterior face of the insulation is twofold.
First things first, a configuration where the window (or door) assembly lines up with the exterior insulation panel reduces thermal bridging from the wall to the window. That’s because the insulation layer adds an effective thermal break, without which heat would have a path through the wall’s non-insulated components to the window assembly. Simply put, by placing the glazing at a depth where the insulation can act as a thermal break will lead to reduced heat loss through the wall.
Secondly, the overwhelming majority of builders prefers the glazing to be flush with the exterior face of the ICF insulation because this configuration saves time, materials, and keeps moisture away. By recessing the window, a crew creates extra work for themselves, including sloping the sill to keep moisture from running under the assembly and flashing the windows. When the glazing sits in line with the exterior insulation panel, there’s little room for moisture to accumulate and flashing the window is a less extensive procedure.
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