What role does the aluminium facing play in internal insulation?

First, leaks must be removed and rising damp identified. A damp wall should not be sealed with a vapour-tight layer in the hope that the problem will disappear. Thermal insulation does not replace repair of the roof, flashings or ground-level protection. The condition of the existing wall determines the further procedure.

Certain PIR boards use facings containing aluminium. These have a high diffusion resistance. They can restrict the passage of vapour through the board surface, but data for the specific product is required. Not every silver material should be regarded as a layer with identical properties.

Joints are equally important. Even a tight surface will not ensure continuity if a gap is left open at the floor. Air can carry moisture behind the insulation. The solution requires compatible materials for connections and designed terminations. A shiny foil alone does not constitute a complete detail.

For an example PIR with a foil facing and λ 0.022 W/(m·K), a 60 mm layer has a calculated R of approximately 2.73 m²·K/W. A 100 mm layer gives approximately 4.55. These are the insulation resistances. The U-value of the entire wall also depends on the masonry, plasters, surface resistances and appropriate corrections.

A large additional resistance should not be added merely because the foil is reflective. The reflection effect requires a specific arrangement with an air space. Foil in direct contact with the next layer does not act as an arbitrarily assumed “additional insulation thickness”. The actual cross-section is needed for the calculation.

Work begins with inspection and assessment of the load-bearing capacity of the surface. Loose plaster, salt contamination and traces of leaks require identification. After removing the causes of moisture, the fixing method is selected in accordance with the chosen system. Not every foam or adhesive is suitable for every facing. It must also be established whether voids behind the board are permissible.

Next, details at the reveals, ceiling and transverse walls are prepared. Once the insulation is installed, the required seals and the finishing layer are applied. The exact sequence follows from the system solution. It should not be replaced by a universal recipe made up of random products.

Insulating a large area while leaving a cold reveal can shift the problem to a narrow strip at the window. Connections to the ceiling behave similarly. Surface temperatures and continuity of insulation must be assessed. Sometimes site conditions limit the thickness, but such a difficulty requires a detail solution.

Electrical boxes and cables can interrupt the airtight layer. Their routing should be determined before installing the boards. An installation layer can be helpful if provided for in the system. Do not drill arbitrary holes later without checking the consequences. Every penetration should have appropriate finishing and sealing.

Check the continuity of insulation, the connections and the condition of the cladding. Verify the details at all boundaries of the area. It is good practice to document concealed locations. The later finished surface will not show whether a gap or damaged membrane was left behind it. The finish must also meet user and fire requirements.

After renovation, monitor humidity and ventilation operation. A tighter enclosure does not remove vapour from the room. A change of use, for example drying laundry, can significantly change the conditions. The insulated wall remains part of a building whose heating and air exchange must work together.

If a composite board with gypsum cladding is used, check the thickness of each layer. For example, 12.5 mm of gypsum is not additional PIR thickness. This distinction matters when calculating insulation, reveal depth and choosing the method of fixing equipment.