Do PIR Insulation Joints Need Taping?

Quick answer: PIR insulation joints do not automatically need taping in every construction. Taping foil-faced PIR joints is one way to create or continue an air and vapour-control layer, but some build-ups use a separate vapour control membrane or foil-backed plasterboard instead.

The correct method depends on the complete roof, wall or floor build-up.

Use suitable foil tape when the PIR is forming the vapour-control layer

If foil-faced PIR is being used as part of the air and vapour barrier, the joints need to be sealed with a suitable insulation or aluminium foil tape so the layer remains continuous.

That includes board-to-board joints and any other junctions that the specified build-up requires to be sealed.

Tape is for sealing, not for holding the boards in place

PIR should be properly supported or fixed as required by the construction. Do not rely on tape as the structural fixing for insulation boards.

The boards should still be cut accurately and fitted neatly before joints are sealed.

A separate vapour control layer can be used instead

Taped foil-faced PIR is not the only way to manage air and vapour movement. Some constructions use a separate proprietary vapour control layer, while others use foil-backed plasterboard where the system allows it.

Follow the construction detail rather than adding tape simply because the insulation is PIR.

Do you need to tape every PIR joint?

Only where the specified build-up requires the PIR facing to form part of the air or vapour-control layer. If another dedicated layer is doing that job, the taping requirement can be different.

For roofs and external walls, moisture control is part of the complete design, so ventilation, membranes and the position of the insulation all matter.