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Lasting performance for long-lasting facades – SREP® makes the difference
Two freshly painted facades – at first glance, they look identical. But over time, the difference becomes clear: one facade turns damp and gray, while the other retains its aesthetic appeal. How is that possible? Silicone resin emulsion paint (SREP®) makes the difference! Let’s take a closer look.
Imagine a duplex facade split in two: one side is coated with a conventional facade paint, the other with a silicone resin emulsion paint (SREP®). At first sight, both finishes appear flawless. Yet the real contrast lies beneath the surface: differences in formulation lead to striking variations in paint performance, durability and appearance over time.
What makes SREP® different?
Conventional facade paints typically contain higher levels of organic binders that form a closed, less permeable film. SREP® coatings, on the other hand, are formulated above the critical pigment volume concentration (CPVC). They contain less organic binder, more pigments and fillers, plus a silicone resin binder and silicone additives. This formulation produces a porous breathable coating that protects walls from water ingress while allowing moisture to escape
Understanding PVC and CPVC
PVC and CPVC are critical parameters for understanding the difference between SREP® and conventional paints:
Microscopic insight: closed vs. open film
Scanning electron microscopy makes the difference visible:
Silicone resin binders contain a large amount of trifunctional silicone units that provide a crosslinking effect.
Getting the chemistry right
Choosing the right silicone chemistry is key to achieving the outstanding properties of SREP®. In conventional facade paints, silicone additives improve workability and water beading but tend to migrate to the surface of the coating. SREP®, by contrast, contains silicone resins – molecules that form a three-dimensional, crosslinked network throughout the entire coating matrix. This network anchors firmly to the substrate, delivering long-lasting protection from water and UV radiation and a harder, more dirt-repellent surface.
How SREP® makes a difference
Water repellency
SREP® exhibits very low water uptake and outstanding water beading. Water repellency remains intact for years.
Breathability
Walls dry efficiently as water vapor escapes through the surface. This minimizes blistering, cracking and microbial growth – ensuring long-term durability.
Dirt pick-up
A harder, low-tack surface minimizes dirt accumulation and enhances dust repellency; facades stay clean for years with minimal maintenance.
UV-stability
SREP® forms a UV-stable network that protects the paint from sunlight and weathering.
Want to dive deeper?
Our video gives you the full details on silicone resin emulsion paints by comparing conventional paint and silicone resin emulsion paint (SREP®) side by side on a split facade. See how the two coatings behave over time and discover the fascinating silicone chemistry behind their performance.
Watch the full video to see why SREP® makes the difference:
How do silicone resin emulsion paints perform in real life?
Lab results are one thing – but they don’t tell the whole story. That’s why we at WACKER were delighted to have the opportunity to test SREP® under real-life conditions on the house of our colleague Dr. Heinz Geich. In 2003, he decided to paint his exterior walls with silicone resin emulsion paints. What does it look like today? We made a house call.
Meet the human network behind the silicone network
Just as SREP® forms a stable network that outperforms conventional paints, our Construction Chemicals & Coatings team operates as a global expert network for quality, sustainability and support. Watch our video to learn more about the chemical network of silicones and meet our experts!
Explore the history of silicone resins
Today, our silicone resins are a gold standard in facade protection – shielding buildings from the sun, wind and rain around the world. Their story began in 1963, when three dedicated WACKER researchers laid the foundation for what would become a global success. Join us on a journey through the history of silicone resins!
How can we help move your project forward?
Do you have questions about silicone resin emulsion paints or are you looking for the right product for your application? Our expert Lenine de Sousa Gomes, Marketing Manager Construction Chemicals & Coatings, Europe, Middle East, Africa and South America, will be happy to advise you!
What our experts say
What really distinguishes silicone resin emulsion paints in practice? And why does silicone chemistry matter more than many assume?
We asked around – with those who should know: our SREP® experts Lenine De Sousa Gomes, Senior Marketing Manager, and Dr. Christophe Cheikh, Senior Technical Manager, share their knowledge and views in a detailed interview.
FAQs about SREP®
1. Why should facade coatings be breathable, i.e., permeable to water vapor?
However new and perfect they may be, most facades contain flaws such as hairline cracks. These are weak spots where moisture can penetrate the facade. The substrate must be able to dry out whenever ambient conditions permit. Otherwise, spalling or other damage will occur. Additionally, dry substrates do not promote the growth of microbes, such as algae and fungi
2. How breathable is a coating of silicone resin emulsion paint based on SILRES® BS?
Because it is a mineral-like coating, silicone resin emulsion paint is just as breathable (water-vapor permeable) as silicate paint and whitewash. The reason for this is its microporous structure, which permits the free movement of gases. In the three-tier classification system used in European standard EN 1062-1 for water-vapor diffusion current density , silicone resin emulsion paint falls under Class 1 (highly permeable).
3. Why is it such an advantage that silicone resin emulsion paint based on SILRES® BS is permeable to water vapor, but at the same time water repellent (beading effect)?
Due to its low water uptake, as little water and moisture as possible penetrate the facade. However, no exterior paint offers 100% protection from damp. That’s why it’s important for the paint system to feature high water-vapor permeability. This is the only way the facade can dry out again. In other words, the masonry can “breathe.”
The combination of these two properties makes silicone resin emulsion paint the prime coating system for facades and is the reason for their extremely high durability and dirt-repellent effect.
4. Does the beading effect mean the building is waterproof?
The beading effect becomes obvious when it rains: water droplets bead up into little spheres and roll off the silicone resin emulsion paint, thus preventing the formation of standing water. This effect ensures an appropriate level of waterproofness. Waterproofness is the property of preventing standing water from penetrating into the substrate even after an extended period of time.
5. What makes silicone resin emulsion paints based on SILRES® BS so durable?
Silicone resin emulsion paints owe their superior durability to the properties of low water absorption combined with high water-vapor permeability. These properties are conferred on the paints by the silicone resin binder, which forms a strongly hydrophobic (water-repellent) network, penetrating deep into the structure of paints and plasters. This permanently protects the facade from UV light and washout.
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