Historic wall — termPIR® AL GK (internal bonding)

When to use this system

Insulating from the inside of a building is a solution reserved for:

• Heritage buildings protected by the regional conservation officer — where facade details (cornices, pilasters, ornaments, original clinker brick) cannot be covered by external insulation.
• Tenement houses in historic centres — where the local zoning plan (MPZP) requires preservation of the original facade appearance.
• Thermal upgrades of party walls — where a building adjoins a neighbouring one on the property line, with no option to insulate from outside.
• Staircases and corridors — where external insulation would be economically unjustified (small wall area).

Why AL GK

termPIR® AL GK is a composite of PIR + plasterboard in a single production step:

• Time savings — eliminates the step of installing separate plasterboard on a frame. After bonding PIR-AL-GK to the wall → joint filling → painting. 3 days instead of 7–10 for traditional technology.
• Low final thickness — 30–110 mm of total insulation + finish (vs 60+ mm of mineral wool + 12.5 mm plasterboard + frame = ~100 mm minimum).
• Class F in internal use — plasterboard acts as a protective layer from the fire safety perspective.

Critical requirements — hygrothermal analysis

WARNING: internal insulation increases the risk of condensation within the external wall (the dew point shifts to the colder side of the masonry, where moisture may occur).

A hygrothermal analysis of the wall is required before selecting the thickness:

termPIR® AL GK thickness	Risk of condensation in masonry
30–50 mm	low — occasional drying is sufficient
60–80 mm	medium — auxiliary vapour barrier required
100–110 mm	high — continuous PE vapour barrier + Glaser analysis required

For historic brick masonry — we typically select 60–80 mm as a compromise between insulating performance and the risk of wall dampness.

Installation requirements

• Seasoning of the existing wall — before insulating, the masonry must be dry (moisture content < 4%). Measure with a moisture meter.
• Substrate levelling — cement-lime plaster, deviations ≤ 5 mm over 2 m. Protruding elements (anchors, cables) must be filled flush.
• Bonding — universal adhesive in 14 dabs per board + perimeter strip (min. 40% of surface). Apply adhesive only on a dry wall.
• Gap from the floor — 10 mm absolutely required (protection against capillary moisture rising from the floor).
• Joints ≥ 5 mm to be filled with PIR assembly foam (chemical compatibility with the core); joints < 5 mm — expansion tape.
• Joint finishing after 7–14 days — time needed for adhesive and foam to stabilise.

Frame-mounted variant

For highly uneven or damp walls, an alternative is the frame-mounted variant (separate system) — metal frame + separate PIR board + separate plasterboard. Less time-efficient, but allows ventilation of the cavity behind the insulation.

Technical documentation

termPIR® Catalogue — Residential Buildings (Gór-Stal, 2022-04-26, pp. 50–52). Class F for the PIR core; final system class per finish (typically non-flammable and non-dripping in ceiling/wall applications with plasterboard).

Layer composition

U-value by insulation thickness

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