Window in three-layer wall — vertical section

Junction function

Window in a three-layer wall — more complex than in ETICS, because it requires two lintels: one in the load-bearing wall (item 04 inner part) and another in the facing wall (item 04 outer part). Both lintels must be independently supported within their own layer.

The vertical detail shows:

1. Load-bearing lintel — reinforced concrete or steel → facing lintel in brick / sand-lime (typically a factory prefabricated unit with openings for the window).
2. termPIR® AL strip above the facing lintel — continues the cavity insulation.
3. Low-expansion installation foam (item 11) — gap between the window frame and the reveal.
4. External sill (item 08) typically in two parts: stone / sheet metal on the facing wall + sealed joint with the frame.

Critical installation aspects

• Facing lintel — typically a reinforced brick / sand-lime prefabricated unit, available from the masonry manufacturer; bearing on the walls on both sides of the window with a 20 cm allowance (load-bearing layer + reinforcement).
• termPIR® AL strip above the facing lintel — narrow (8–15 cm) but critical; without it, a linear thermal bridge of ψ ≈ 0.3 W/m·K forms above every window.
• Installation foam (item 11) must be LOW-EXPANSION (standard foam will deform the window frame).
• Window frame fastening — frame anchors must be fixed to the load-bearing wall (NOT the facing wall!); the facing wall moves thermally and will not support the window.
• External sill (item 08) laid on a waterproofing layer of EPDM 200 mm; 5% slope, 30 mm drip edge projecting beyond the facing façade.
• Slab ring beam (item 10) — anchor ties with full ring beam reinforcement in both layers; important for structural rigidity in earthquakes (Poland zone I/II — not significant, but required by PN).

Documentation

Technical Catalogue termPIR® — Residential Buildings (Gór-Stal 2022), page 39 — Three-layer wall, window detail, vertical section. Scale 1:10.

Components in this junction