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Passive Purple Airtightness Success: Warm Roof Retrofit for Luxury Apartments in Tottenham

The Challenge: Airtightness in Complex Warm Roofs

Warm roof structures and joist zones are some of the most notorious areas for air leakage in construction. Achieving airtightness in these spaces can be extremely challenging, especially during retrofit projects where precision and performance must meet architectural complexity.

That was exactly the case for this luxury apartment retrofit in Tottenham, where a brand-new warm roof structure had to be integrated onto an existing block of apartments. With multiple skylights, dormers, and even 360-degree turrets, the project demanded airtightness solutions that went far beyond traditional tapes and membranes.

The Solution: Passive Purple

Once the hand-cut roof was completed, the 220mm roof rafters were filled with spray foam insulation supplied by Lapolla UK. This gave the structure its thermal foundation, but airtightness was still critical.

Enter Passive Purple—the world’s most advanced liquid-applied airtight vapour control membrane.

  • Detail sealing first – Using Passive Purple Brush, the Intelligent Membranes team sealed dormers, skylights, turrets, and other hard-to-reach areas prone to air leakage.

  • Full coverage second – The final application of Passive Purple spray provided a seamless, flexible airtight vapour control layer across the entire roof.

This combined system delivered a complete airtight envelope while making light work of awkward angles, curves, and penetrations that would have been a nightmare with traditional membranes.

The Results: Airtightness Made Easy

The luxury apartments now benefit from a fully airtight and vapour-controlled warm roof, ensuring energy efficiency, long-term durability, and comfort for residents.

For the client, the benefits went even further:

  • Time-saving – Liquid application drastically reduced labour hours compared to tapes and sheets.

  • Guaranteed performance – No weak spots, overlaps, or adhesion failures.

  • Precision finish – Even complex circular details and angled joints were easily sealed.

In short, Passive Purple turned a potentially difficult airtightness challenge into a fast, guaranteed solution.