In the internal insulation of window reveals, slim, reliable connection details are particularly important. This applies especially in existing buildings when exterior insulation is not possible or the reveal offers very little space for the build-up. The question of wood fiber or mineral foam for reveal insulation in 2026 therefore cannot be answered in general terms. What matters are the available thickness, moisture management, and the proper formation of the connection joints.
When narrow reveals place special demands
In internal insulation of window reveals, reducing thermal bridges at the window connection is a central issue. Especially in narrow reveals, planners and installers must work with thin reveal boards so that fittings, window sashes, and adjacent components remain functional. Technical rules and manufacturer systems therefore often rely on coordinated adhesive and reinforcing mortars as well as carefully formed connection joints. In practice, it is less about individual boards alone and more about a functioning overall system for critical connection areas.
Mineral foam: useful for slim and critical connections
Mineral foam boards are used as mineral, capillary-active internal insulation boards. For reveals and other sensitive connection zones, they are a typical material because they are non-combustible and suitable for moisture-balancing constructions. In tight window connections, this is a clear advantage: where space is limited, slim, vapor-permeable reveal