Products that preserve history
Breathable Airtightness for Heritage & Retrofit Projects
The Intelligent Membranes team were asked to help answer an age-old question:
How do we retrofit buildings for airtightness while still allowing the structure to breathe?
With historic buildings, this challenge is even greater. Lime walls often need consolidation to create a stable substructure for any liquid-applied membrane — but over-sealing them can damage the building fabric.
That’s where our vapour-open airtight solutions come in. Passive Purple External and Passive Purple X are fully airtight yet vapour-open, allowing moisture to escape naturally while meeting modern airtightness performance standards. This ensures the structure stays healthy, preserving heritage fabric while delivering 21st-century comfort and efficiency.
Respecting the Past, Building for the Future
Historic buildings can keep their traditional character while benefiting from modern performance. At Intelligent Membranes, we use sustainable, VOC-free materials to protect heritage integrity and improve building comfort. The result? Traditional structures that are healthier, warmer, and more energy-efficient for their occupants.
Two Common Problems, Two Proven Solutions
Lime Prime – A hand-spray or brush-applied base coat that impregnates and strengthens lime-based substrates while keeping them fully breathable. Consolidates fragile surfaces, ensuring a solid foundation for follow-on coatings like Passive Purple External or Passive Purple X.
SuperGrip – Creates a bonding layer over Passive Purple or Passive Purple External, enabling dot-and-dab plasterboard fixing, skim coats, or screed treatments. Saves contractors time and ensures finishes adhere reliably to airtight membranes.
Passive Purple – Airtight Retrofit Made Simple
For retrofits, Passive Purple is a breakthrough solution. Its liquid-applied nature creates a seamless airtight barrier over complex junctions, irregular surfaces, and hard-to-reach areas — perfect for the unique challenges of retrofit work.
In heritage projects, Passive Purple External and Passive Purple X offer airtightness without trapping moisture, keeping the building fabric breathable and healthy. This combination of airtightness and vapour openness means contractors can:
-
Dramatically cut heat loss
-
Keep interiors comfortable year-round
-
Prevent condensation and mould
-
Maintain historic integrity while meeting modern standards
With Intelligent Membranes products, you can future-proof historic and existing buildings — achieving exceptional airtightness, preserving breathability, and delivering the comfort and performance today’s occupants expect.
Render Prime ,Lime Prime and SuperGrip
Heritage & Modern Surface Solutions – Lime Prime, IM Primer & SuperGrip
On construction sites, contractors and architects often face two persistent challenges:
-
Treating and preparing lime-based heritage structures without compromising breathability.
-
Bonding finishes to high-performance airtight membranes like Passive Purple.
Our Heritage Range and new bonding solutions solve both problems.
Lime Prime – Breathable Heritage Base Coat
Designed specifically for Grade-listed and heritage buildings, Lime Prime is a hand-spray or brush-applied base coat that treats and primes lime-based substructures without sealing them.
-
Fully impregnates the surface, becoming part of the substrate.
-
Maintains full breathability, essential for historic building health.
-
Improves surface stability while preparing it for follow-on materials.
This ensures heritage fabric is both protected and ready for further works — all while respecting conservation principles.
IM Primer – Reliable Substrate Preparation
IM Primer is a versatile solution for modern and mixed-material projects, ensuring strong adhesion and an even, stable base for a range of finishes. Ideal for use where substrate conditions vary.
SuperGrip – Bonding to Airtight Membranes
Before SuperGrip, the only option for applying finishes to Passive Purple or Passive Purple External was recommending polymer adhesives we had tested ourselves. Now, SuperGrip changes the game.
-
Sits directly on top of Passive Purple products
-
Enables dot-and-dab plasterboard fixing
-
Compatible with skim coats and screed treatments depending on the job
By integrating SuperGrip into your workflow, contractors save time sourcing other adhesives — and time is everything when finishing projects on schedule and within budget.
In short:
-
Lime Prime protects and primes heritage lime substrates while keeping them breathable.
-
IM Primer prepares mixed or modern substrates for finishing.
-
SuperGrip enables fast, reliable finishing over airtight membranes.
Together, they remove two common site headaches and keep projects moving smoothly.
Our Affiliations
-
-
