Why Breathability Matters More Than You Think in Building Materials

When it comes to modern construction, performance is often measured in terms of strength, durability, and cost. But there’s one critical factor that’s frequently overlooked, breathability. Many commonly used materials in today’s building envelope are designed to block moisture. On paper, that sounds like a good thing. In reality, it can create a hidden problem

The Hidden Risk of Trapped Moisture

When materials don’t allow moisture to escape, water vapour becomes trapped within the wall system. Over time, this can lead to:

• Mould and mildew growth
• Degradation of internal components
• Poor indoor air quality
• Health risks for occupants

These issues aren’t always visible at first, but they can have serious long-term consequences for both the building and the people inside it.

The Breathable Alternative

Breathable systems take a different approach.
Instead of trapping moisture, they allow vapour to pass through and escape, helping the building “breathe” naturally. This reduces the risk of condensation build-up and keeps the wall system dry and stable over time. The result?

• Healthier indoor environments
• Reduced risk of mould and mildew
• Improved longevity of the structure
• Greater overall building performance
• Building for the Long Term

Choosing breathable materials isn’t just a technical decision. It’s a commitment to healthier buildings and better outcomes for the people who live and work in them. Not All Materials Perform the Same; this is where the difference becomes critical.

Materials such as KS007 and KB025 are designed with breathability in mind, allowing moisture vapour to pass through the system and escape naturally whilst maintaining the highest levels of water tightness outside - in.

In contrast, many competitor materials act as vapour barriers rather than breathable layers. While they may resist moisture ingress, they can also trap vapour within the wall build-up, increasing the risk of condensation and associated issues.

Interface Sealing Membrane HD (KS007) is a high-strength polyester membrane designed for external perimeter sealing of windows and doors. Permanently UV resistant, airtight, and fully watertight, it offers long-term protection against the elements while maintaining structural integrity. Its durability makes it ideal for demanding environments where performance cannot be compromised. Learn More

KB025 FR Membrane Adhesive complements KS007 perfectly. This chemically neutral, low-odour adhesive is easy to work with and provides excellent bonding performance, even on slightly damp surfaces. Once cured, it remains permanently elastic while delivering high mechanical strength, ensuring the seal can accommodate movement without failure.  Learn More

Need Project Support?

At Klasse, we are committed to offering comprehensive support throughout the duration of your project. From the initial specification review to the final site inspection, we are here to assist you at every stage when you choose to work with our products.