Township of Langley Educational Mockups

This detail shows the below-grade to wall air barrier transition for an exterior air barrier approach. The transition must provide a continuous, sealed connection between the foundation and framed wall assembly. Product compatibility is critical, especially where air barrier materials must adhere to wet concrete surfaces. Proper surface preparation, including cleaning and priming where required, is key to successful installation.

This detail shows an exterior air barrier strategy using the water-resistive barrier (WRB). All laps, seams, and accessories must follow manufacturer requirements. Compatible tapes and accessories should be used, and all vertical and horizontal seams should be sealed continuously to maintain air barrier continuity. 

This detail shows lower window corner detailing where waterproofing and air barrier continuity must be maintained in a WRB-based exterior air barrier approach. Compatible self-adhered sill products should be used at corners, with gussets where required. Avoid stretching materials that have memory, as they may pull back over time and compromise water management and air barrier continuity. 

This detail shows upper window corner detailing where waterproofing and air barrier continuity must be maintained in a WRB-based exterior air barrier approach. Use compatible tape products at corners. Avoid stretching materials that have memory, as they may pull back over time; use gussets where required instead. 

Windows are a critical part of the air barrier system. The window frame must connect continuously to the wall air barrier membrane to maintain airtightness and reduce air leakage. To achieve this, continuity and compatibility between the window frame, membrane, and sealants must be maintained. Caulking beads must meet manufacturer requirements for adhesion and long-term durability. For both exterior and interior air barrier strategies, the sealant is typically applied from the indoor side to allow moisture to drain to the outside. When using a back dam, sealant must “bleed out” for visible inspection and quality assurance. With clip-mounted window systems, sealant is required both below and above the clips to maintain air barrier continuity.

At the top of the wall, the air barrier system must transition continuously from the exterior wall air barrier to the interior ceiling air barrier at the attic level. In homes with unconditioned attics, the ceiling air and vapour barrier often becomes the primary roof air barrier. Maintain continuous airtight connections between the wall and ceiling air barrier systems. A common approach is a “tape-to-tape” transition at the top plate connection area. Proper sequencing between trades and contractors is critical to avoid gaps or damage before completion. Materials, tapes, and membranes must be compatible and durable for long-term performance. 

Electrical system penetrations through the air barrier can be sealed using a gasket system. In this detail, an EPDM gasket is used to create an airtight seal around the conduit penetration through the membrane. Sealing a round conduit to a flat membrane surface with tape alone can be difficult and time-consuming. A gasket approach provides a simpler and more reliable airtight seal, while also allowing for easier future repair or conduit replacement. Material compatibility is critical: the tape must properly adhere to both the EPDM gasket and the surrounding membrane to maintain long-term airtightness. 

Mechanical penetrations through the air barrier, such as a 4-inch dryer vent, can be sealed using a gasket system. In this detail, an EPDM gasket is used to create an airtight seal between the vent penetration and the membrane. For round duct or vent penetrations, this approach provides a reliable seal without relying on tape alone. Materials must be compatible with the gasket and surrounding membrane, and the duct assembly should be properly supported for long-term durability. 

This detail shows the slab-on-grade to interior foundation wall air barrier transition, using polyethylene sheeting to maintain a continuous airtight layer at the junction. Proper sequencing between trades is critical so the air barrier can be installed, connected, and inspected before concealment. At all transitions and junctions, the air barrier system must remain continuous to preserve airtightness. Material compatibility between polyethylene, tapes, primers, and sealants is essential. Some sealants, such as acoustic sealant, are intended to perform under compression and may fail if applied incorrectly. Airtight connections should remain visible and inspectable before finishes are installed. 

This detail shows an interior air barrier connection at the rim joist using polyethylene sheeting and sealant to maintain continuity between building assemblies. The air barrier system must remain continuous across all transitions and junctions. Proper sequencing between trades is critical to allow the connection to be installed correctly and remain continuous. Material compatibility between polyethylene, tapes, primers, and sealants is essential for long-term durability. Taped or sealant-based approaches may be used depending on the application and site conditions. Airtight connections should remain visible and inspectable before finishes are installed. 

This detail shows an alternative rim joist approach using XPS insulation for thermal and vapour control. In this mock-up, the air barrier has been applied on the exterior; however, XPS may also be used as an interior air barrier only if all joints, edges, and penetrations are properly sealed. Continuity of the air barrier system is critical at all joints and transitions. If XPS is used as part of the air barrier system, sealant must be applied around the perimeter and at all penetrations to maintain airtightness and durability. Material compatibility between the XPS, sealants, and adjacent materials must be verified. Not all XPS products are tested or approved for use as air barrier materials, so product suitability should be confirmed. Quality control, inspection, sequencing, and careful installation are essential before concealment. 

This detail shows polyethylene sheeting used as both the vapour barrier and the air barrier by sealing membrane joints and transitions. When polyethylene is used as an air barrier, all joints, penetrations, and transitions must be sealed continuously. Acoustic sealant creates an airtight joint only when compressed, such as behind drywall. In this detail, electrical tape is used for demonstration purposes only to show the intended location of the acoustic sealant bead. The lower black sealant is a non-compression sealant used to control air leakage below the wall bottom plate. When 6 mil polyethylene is used only as a vapour barrier and not as an air barrier, sealing the joints is typically not required. 

This detail shows the window as part of the air barrier system from the interior side. The window frame must connect continuously to the wall air barrier system to maintain airtightness. Compatibility between the window frame, membranes, tapes, and sealants is critical. Sealant connections between air barrier materials, whether to a WRB such as Tyvek or to polyethylene sheeting, are typically installed from the interior side so incidental moisture can dry toward the exterior. 

This detail shows the exterior WRB used as the air barrier membrane, such as Tyvek, being brought over the top plate and into the interior space for later connection to the polyethylene ceiling air barrier. This tape-to-tape method uses compatible, vapour-appropriate high-acrylic tape to connect the exterior wall air barrier to the interior ceiling air barrier. Proper sequencing, material compatibility, and inspection before concealment are critical to reduce air leakage. 

This detail shows an alternative approach for transferring the exterior WRB used as the air barrier membrane, such as Tyvek, at the top of the wall. A separate strip of WRB is installed for later connection to the top floor ceiling polyethylene air barrier. The exterior wall air barrier and interior ceiling air barrier must connect continuously. Proper sequencing between framing, membrane installation, and interior air barrier work is critical. Transitions should remain visible and inspectable before concealment. All joints should be taped and sealed before the ceiling is concealed. Careful detailing is required to reduce air leakage; if leakage is found, an approach similar to Detail 15 may be used. 

This detail shows an electrical penetration through the air barrier system, where the polyethylene vapour barrier is being used as the air barrier. All penetrations must be sealed to maintain airtightness and continuity. Fire putty may be used around electrical penetrations to help maintain both fire resistance and airtightness, but its flexibility, durability, adhesion, and suitability for the intended application should be verified. Material compatibility between the polyethylene, sealants, tapes, and fire stopping products is essential. Backing support may be required depending on the product and installation method. 

This detail shows a pipe penetration through the interior top of wall to ceiling air barrier transition. A gasket is used to create an airtight seal between the pipe and surrounding air barrier membrane without relying on tape alone. Materials must be compatible, and the pipe should be properly supported to maintain long-term airtightness and durability.