What is airtight tape?
Airtight tape is self-adhesive tape used to seal seams, overlaps and joints in the insulation and airtight layer of a building. The aim is to make the layer that holds back air and moisture continuous, so heat does not leak out through gaps and no moisture soaks into the structure. In electrical work “insulation tape” means something else (insulating PVC tape around wires); in building work it refers to airtight and vapour-barrier tapes.
Types and application
There are different tapes for different places in the building envelope:
- Vapour-barrier tape — for airtight jointing of vapour barrier or vapour control membrane sheets on the inside.
- Seam tape for insulation boards — for taping the joints between rigid insulation boards (such as PIR or EPS).
- Connection tape — flexible tape for the transition to frames, penetrations and beams.
Points to watch
For a lasting airtight result, good adhesion is crucial:
- Clean, dry substrate — dust, moisture and grease weaken the adhesive; prime the substrate first if needed.
- Right tape in the right place — choose interior or exterior tape based on vapour permeability; a vapour barrier belongs on the warm (inside) face.
- Press down well — press the tape firmly with a roller or spatula for full contact.
In high-quality building the airtightness of the tape and joints is checked with a blower-door test. Choose tape with a long expected life, because replacing it behind finishes is later almost impossible.
Related terms
- Insulation
- Vapour barrier
- Vapour control layer
- Vapour-open building
- Blower-door test
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