Swimming pool vapour control membrane with Passive Purple
PASSIVE PURPLE: THE ULTIMATE AIRTIGHT MEMBRANE FOR SWIMMING POOLS AND HIGH-HUMIDITY SPACES
When it comes to airtightness and vapour control in swimming pools, spa areas, and wet leisure facilities, few products can handle the challenge like Passive Purple. Constant humidity, warm air, and evaporating water create an aggressive environment that pushes materials to their limits. That’s why choosing the right airtight membrane and applying it at the correct thickness is vital. At Intelligent Membranes, we tailor the performance of Passive Purple by adjusting its film thickness to match the humidity levels of the space. The result? Consistent airtightness, reliable vapour resistance, and long-term durability, all from one product
WHY SWIMMING POOLS NEED SPECIAL VAPOUR CONTROL
Swimming pools and wet areas maintain high internal humidity (typically 60–70% RH). This constant moisture creates vapour pressure that tries to escape through the walls and ceilings. If the vapour barrier isn’t resistant enough, that moisture can condense inside the structure, leading to mould, rot, and costly repairs. That’s why vapour control membranes in pool buildings must be specified with care, balancing airtightness, vapour diffusion, and breathability.
TEST CONDITIONS VS. REAL-WORLD HUMIDITY
You may have seen Sd values tested under 39/69% relative humidity; that’s simply the EN ISO 12572 laboratory standard for measuring vapour resistance. In real-world buildings, humidity looks very different: Environment Typical RH (%) Notes Standard dwellings 40–55% Normal living conditions. Bathrooms & kitchens 55–65% Short humidity spikes. Swimming pools 60–70% Constantly humid environment. Saunas/plant rooms 70–80% High and sustained moisture.
ADJUSTING PASSIVE PURPLE FOR POOL ENVIRONMENTS
Passive Purple is unique; its Sd value increases with film thickness, meaning you can tailor vapour resistance without changing products.
| APPLICATION | TYPICAL RH | DRY FILM (MM) | SD (APPROX.) |
|---|---|---|---|
| STANDARD DWELLINGS | 40–55% | 0.4 | 14.1M |
| SWIMMING POOLS | 60–70% | 0.6 | 21.1M |
| HIGH-HUMIDITY ZONES | 70–80% | 0.8+ | 28M |
By applying more Passive Purple, you increase vapour resistance, keeping moisture where it belongs, inside the pool, not in your wall build-up.
REAL-WORLD APPLICATION
For a recent indoor pool project, the air humidity was maintained around 65% RH. Instead of specifying a separate vapour control layer, we increased the Passive Purple dry film thickness to 0.6 mm, raising the Sd value from 14 m to over 21 m. This simple adjustment provided robust vapour control, consistent airtightness, and complete compatibility with subsequent finishes such as render, tile adhesive, and decorative coatings.
BENEFITS OF PASSIVE PURPLE IN POOL CONSTRUCTION
✅ Seamless airtight membrane with no joints or tape failures
✅ Adjustable Sd value – control vapour resistance by thickness
✅ Fire-rated and VOC-free, safe for occupied spaces
✅ Perfect for Passivhaus, retrofit, and new-build leisure projects
✅ Applied by spray, brush, or roller for total design flexibility
INTELLIGENT AIRTIGHTNESS FOR EVERY ENVIRONMENT
Humidity varies from room to room; your airtight solution should too. Passive Purple adapts effortlessly to every humidity zone, ensuring airtightness, vapour resistance, and energy efficiency are never compromised. Whether you’re working on a residential pool, hotel spa, or public leisure centre, our team can help you specify the correct film thickness to achieve the perfect balance between airtightness and vapour control.