Every pipe, conduit, duct, or fastener that penetrates the building enclosure represents a potential leak point. This article outlines best practices for air sealing and flashing penetrations through WRBs (Water-Resistive Barriers) and air barriers to ensure continuous control layers and long-term performance.
Common Penetration Types
- HVAC refrigerant and exhaust lines
- Electrical conduit, meter boxes, and service entrances
- Plumbing pipes and hose bibs
- Roof fasteners, brick ties, and anchor bolts
Air and Water Barrier Detailing
Use pre-formed gaskets or fluid-applied flashing to seal penetrations. Stretchable flashing tape can also be used for rectangular boxes or conduit banks. Penetrations should slope downward toward the exterior. WRB should be lapped over all flashing in shingle fashion. Fasteners penetrating WRBs should be self-sealing or gasketed where possible.
Sequencing and Redundancy
- Install pipe sleeves or escutcheon plates for durability and serviceability
- Flash pipe boots or stretch tape prior to installing cladding
- Use sealant and backer rod behind escutcheons where airtight seals are required
- Field test high-risk penetrations using water spray or smoke tests
Quality Assurance Practices
- Inspect sealant coverage and tool marks for consistent adhesion
- Check for compression of gaskets or boots to achieve airtightness
- Photograph all flashed penetrations before cladding install
- Coordinate between MEP trades and enclosure teams to avoid post-installation patching
For commercial projects, include a penetration schedule in QA/QC documentation and verify sequencing at each inspection phase.
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