Uninsulated floor lines, slab edges, and steel shelf angles are among the most common sources of thermal bridging in commercial and multifamily buildings. This article explores best practices for detailing and mitigating these thermal bridges to improve building performance.
Common Thermal Bridge Locations
- Steel shelf angles supporting brick or stone veneer
- Slab edges at balconies or intermediate floors
- Exposed concrete at cantilevers or curtain wall anchors
- Breaks in continuous exterior insulation at floor lines
Design and Detailing Solutions
- Use thermal break pads between shelf angle and backup structure
- Offset cladding support to allow continuity of exterior insulation
- Install mineral wool or polyiso insulation between slab edge and cladding
- Integrate insulation behind shelf angles using Z-girts or thermal clip systems
Air and Vapor Control at Floor Lines
Air barrier membranes must continue across slab edge transitions. Use transition membranes, liquid flash, or factory pre-formed corner tapes. Avoid discontinuities where WRB terminates at intermediate floors without tie-in to the above floor. Include expansion joints where differential movement is expected.
Thermal Analysis and Energy Modeling
- Use THERM or other 2D modeling software to quantify heat loss at bridging locations
- Simulate condensation risk and surface temperature under worst-case climate conditions
- Factor in linear thermal transmittance (psi-values) into whole-building energy models
Including thermal break solutions in early design phases can improve envelope energy ratings by 10–20% in cold climates.
QA and Field Installation Tips
- Inspect shelf angle anchoring and backup wall insulation continuity
- Photograph insulation and air barrier sequencing before cladding concealment
- Confirm adhesive flashing adhesion at corners and membrane overlaps
- Review steel bracket connection details for alignment and spacing
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