Installation in the thermal envelope coordinates support, insulation, airtightness and water drainage. This Lab shows a review method, not a certified detail.
Assumptions and objective
Compare positions of the same window in an externally insulated wall. Without frame, fixing and material geometry, no optimum offset or numerical ψ is assigned.
Thermal model
Uw describes the product, while the installation bridge describes its junction. Compare sections using the same boundaries, reference dimensions and material properties.
Support and movement
Fixings must transfer loads into a suitable substrate and accommodate expected movement. A thermally attractive detail does not prove bracket or fixing capacity.
Three joint functions
Coordinate internal airtightness, joint insulation and external weather protection with drainage. Sills, thresholds and corners need their own details, not just a typical vertical section.
Verification and limits
Before closing reveals, inspect substrate, joints and drainage. Photos and airtightness checks document workmanship but do not replace thermal analysis or water-resistance testing.
| Item | Parameter | Check / result |
|---|---|---|
| Product | Uw | Documentation |
| Installation | ψ and surface | Model |
| Workmanship | Support, joints, water | Inspection |
What this means for your project
Agree complete installation details before ordering windows. Assign responsibility for support, thermal and airtightness checks at every junction.
Sources and scope of review
- PHI Passipedia — Window installation thermal bridges
- ISO 10211:2017 — Thermal bridges: heat flows and surface temperatures
- PHI Passipedia — Airtightness measurements
Related reading
- Energy-Efficient Windows: Which Parameters Really Matter
- Uw, Ug, Uf and Psi: Reading Window Performance
- Airtightness: What It Is and Why It Matters