
Interno
Internal airtightness and vapour control in one liquid system. The inside face of your walls and roof is where the airtight line lives, and it’s where most air tests are won or lost. Instead of sheets, laps and tape everywhere, our liquid-applied vapour control layer (VCL) goes on as one seamless airtight coat.
🔗 One coat, both jobs. Passive Purple is the airtight layer and the vapour control layer in a single membrane. More worried about condensation, damp or “do I need a VCL?” than an air test? Read the vapour control side.
The internal airtight system
- Bulk areas: Passive Purple spray or roller applied: airtight, smoke-tight vapour control paint, Passivhaus certified and BBA approved.
- Junctions & penetrations: Passive Purple brush grade worked into corners, joist ends and service penetrations.
- Frames & board joints: IM Fleece Tape, plasterable and vapour-open.
- Gaps & movement joints: Passivhaus airtight sealant.
- On-show finishes: Airtight White: the same membrane in VOC-free white, smart enough to leave exposed or paint over.
Explore the full VCL membrane collection and airtight paint range.
Why it beats sheet VCLs
A liquid VCL can’t be torn, stapled through or left flapping at a lap joint. It bonds to blockwork, concrete, timber, OSB and plasterboard, cures flexible so it moves with the building, and the purple (or white) finish makes quality control visual, so if it’s coated, it’s sealed. Plaster and dot-and-dab go straight over it with Supergrip primer.
Learn more
- What is a vapour control layer? VCL explained
- Builder forgot the vapour control layer? How to fix it
- The complete internal airtightness kit
- Sealing joist ends — the hidden airtightness weak point
- How to pass an airtightness test — the pre-test checklist
- Retrofit airtightness: seal an existing house without ripping it apart
Shop Airtight Paint & Membranes
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InternoOfertaPrecio habitual A partir de £39.99 GBPPrecio habitual£50.00 GBPPrecio de oferta A partir de £39.99 GBPOferta -

Pintura Passive Purple - Control de vapor, hermética y a prueba de humo (11,4 kg) - Aplicación con pulverizador o rodillo
Short spec • 11.4 kg
Licenciatura en Administración de EmpresasPrecio habitual £99.99 GBPPrecio habitual£119.99 GBPPrecio de oferta £99.99 GBPOferta -
Sellador hermético Passivhaus - 600 ml
Short spec • 840 g
Licenciatura en Administración de EmpresasPrecio habitual A partir de £12.00 GBPPrecio habitual£150.00 GBPPrecio de oferta A partir de £12.00 GBPOferta -

Membrana impermeabilizante exterior impermeable y resistente al fuego Passive Purple (5 kg) - Color Purple Brush
Short spec • 5.0 kg
Precio habitual £55.99 GBPPrecio habitual£69.99 GBPPrecio de oferta £55.99 GBPOferta -

Membrana impermeabilizante exterior ignífuga Passive Purple (10 kg) - Aplicación en aerosol/rodillo
Short spec • 10.0 kg
KIWA PassivhausPrecio habitual £119.99 GBPPrecio habitual£129.99 GBPPrecio de oferta £119.99 GBPOferta -
Precio habitual £28.80 GBPPrecio habitual
Precio de oferta £28.80 GBP -
Interno/ExternoOfertaPrecio habitual £119.99 GBPPrecio habitual£129.99 GBPPrecio de oferta £119.99 GBPOferta -
Interno/ExternoOfertaPassive Purple X (5 kg) Aplicado con brocha
Short spec • 5.0 kg
Precio habitual £55.99 GBPPrecio habitual£69.99 GBPPrecio de oferta £55.99 GBPOferta





