The most important application of PIR boards without cladding is thermal insulation of external walls in ETICS thermal insulation systems. Boards without cladding allow for perfect adhesion of the adhesive to the entire surface of the board. This allows loads to be transferred from the outer layer to the building's supporting structure through the insulation board. In addition, unclad PIR boards are ideal for thermal insulation on the inside of structures in contact insulation of walls, ceilings or roofs. In such applications, the boards are usually fixed mechanically using expansion plugs or screws. Unclad PIR boards can also be used in seamless insulation. In such cases, the boards are welded together by welding the edges using a special electric PIR welding machine or by foaming the joints with a special single-component polyurethane foam.