These figures show how to do these air sealing details as part of an exterior wall retrofit that includes adding rigid foam insulating sheathing to the wall. Flashings are needed wherever a drainage plane is terminated as at a roof edge or the bottom of a wall, or where the drainage plane is interrupted as at openings, the intersection of assemblies, control joints, or penetrations of the drainage plane.įigures 2 to 7 show detail drawing for several air sealing details. Flashings are integrated with the water control layer, creating for all practical purposes a flashing for the entire assembly. Flashings are the most underrated of building enclosure components and are arguably the most important. Protection is typically provided by flashings which might be metal as shown in Figure 1 or self-adhering flexible flashing tape). The water control layer is often referred to as the drainage plane, the water-resistive barrier (WRB), or the water control layer. The materials that form the water control layer overlap in a shingle fashion or are sealed so that water drains down and out of the wall. Water control layers are interconnected with metal and flexible flashing s around windows, doors, and other penetrations through the building enclosure to provide a continuous path to drain water to the exterior of the building. Water control layers are water-repellent materials (building paper, house wrap, sheet membranes, liquid-applied coatings, or taped and sealed rigid insulation boards) that are located behind the cladding (the siding) and are designed and constructed to protect the wall sheathing by from any rain water that might get through the cladding. In most walls, a water control layer protects the structure. While these elements are needed for functional reasons and to add character and amenity to buildings, they can complicate the continuity of the building enclosure functions, including the air, water, vapor, and thermal control layers. When an exterior wall is being upgraded by removing exterior cladding, there are several elements within the field of the wall that “interrupt” the wall assembly, such as pipes, vents, wiring, windows, doors, and architectural elements. See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and EPA Indoor airPLUS. Department of Energy’s Standard Work Specifications. Attach to furring strips.įor more on roof/wall connections, see the U.S. Install a trim block over the duct/pipe and install the metal cap flashing.Install sheathing tape flashing and wood blocking for trim.Install insulating sheathing and vertical wood furring strips.Apply a bead of sealant around the duct/pipe penetration.Install a continuous air/water control membrane (such as house wrap, fully adhered membrane or liquid applied membrane) with a hole for the vent or pipe.Prepare the wall sheathing to receive the air/water control membrane. Remove the existing cladding and trim.When, not if, the water gets behind the veneer or cladding this system will fail and is often catastrophic for the structure.Install flashing integrated with air and water control layers around piping, vents, and other wall penetrations as part of an exterior wall retrofit as follows: This is reliant on the water staying on the outside of the veneer or cladding for this system to work correctly. A mistake often made in construction is installing the flashing on the outside of the cladding or veneer, then installing a counter flashing over it. Because of the small vertical distance above the flashing, a counter flashing would be ideal instead of some type of cladding or veneer. The skylight has a very small vertical height where the flashing meets it, unlike a gable wall for example, which is often tall. The only time counter flashing would make sense is a situation like a skylight. This means that counter flashing would not be necessary if the flashing is installed that way. The reason for this is the fact that flashing should be installed behind the WRB. In my opinion counter flashing should be very rarely used on wall sections.
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