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General questions and answers on SREPGeneral questions and answers on SREP

1. Why should we coat facades with breathable (water-vapor-permeable) systems?

All facades contain flaws (e.g. hairline cracks). These are weak spots, where moisture can penetrate into 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.
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2. How breathable is a coating of silicone resin emulsion paint?

Silicone resin emulsion paint is a mineral-like coating and is accordingly just as breathable (water-vapor permeable) as silicate paint and whitewash. The reason for this is its microporous structure, which permits free movement of gases. In the 3-class classification used in European standard EN ISO 7783-2 for water-vapor diffusion current density, silicone resin emulsion paint falls under Class 1 (highly permeable).
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3. Why is it such an advantage that silicone resin emulsion paint is permeable to water vapor, but at the same time water-repellent (beading effect)?

Because the paint is permeable to water vapor, the masonry is able to breathe. The beading effect prevents water absorption. 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.
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4. How long do silicone resin emulsion paints retain their beading effect?

The beading effect of silicone resin emulsion paints is apparent during weathering (rain, snow etc.) and is retained throughout the coating’s service life. The reference objects show how a treated facade keeps its perfect appearance even after many years.
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5. Is the beading effect (Lotus Effect®) the same as waterproofness?

The beading effect can be witnessed, for example, when it rains: water droplets bead up into little balls and roll off the silicone resin emulsion paint, thus preventing the formation of standing water. This effect also ensures the appropriate waterproofness. Waterproofness is the property of preventing standing water from penetrating into the substrate even after an extended period of time. The Lotus Effect® is a registered trademark which stands for an especially pronounced beading effect.
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6. What makes silicone resin emulsion paints so durable?

Silicone resin emulsion paints owe their great 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, but at the same time is just as mineral in nature as quartz.
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7. What exterior coating system will reduce fungal and algal growth?

Dry facades are less prone to attack by algae, fungi and mold than damp ones. Mineral-type coatings are less susceptible than thermoplastic coatings. Silicone resin emulsion paints keep facades dry. They are non-thermoplastic, mineral-type coatings and thus provide protection against the growth of microorganisms. For facades that are highly at risk, silicone resin emulsion paints are available which contain additional protection against microorganisms.
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8. Are silicone resin emulsion paints mineral or organic?

The binder in silicone resin emulsion paints comprises 50 % mineral-type silicone resin and 50 % polymer emulsion. The paints thus combine the useful properties of organic and mineral coatings in a single system.
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9. Have silicone resin emulsion paints proved successful over the long term?

Silicone resin emulsion paints have been used successfully for 40 years. More than a million buildings all over Europe have been coated with these paints, and many of them have endured over 20 years without needing any further renovation.
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10. Can all kinds of paint be overpainted with silicone resin emulsion paint?

Provided they are suitably prepared and cleaned, all kinds of paint can be overpainted with silicone resin emulsion paint (see also Question 16: ), including firmly adhering emulsion coatings. However, to avoid compromising the silicone resin emulsion paint’s breathability, old coats of emulsion paint must be stripped off or removed mechanically.
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11. Can freshly plastered facades (mineral plasters) be coated with silicone resin emulsion paint?

As a rule, freshly plastered facades cannot be painted until the plaster has set (carbonation), which usually necessitates re-erecting the scaffolding. Silicone resin emulsion paints, by contrast, can be applied to fresh mineral plaster right away, since they are highly permeable to CO2 and thus do not impede carbonation (CO2permeability guarantee).
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12. Can silicone resin emulsion paint be applied directly to facades with salt damage?

Substrates with salt damage must always be properly repaired first: remove all of the damaged substrate, apply repair plaster and a silicone primer. Then you can paint the facade with silicone resin emulsion paint.
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13. What is the function of a silicone-based primer?

The paint/substrate interface is the Achilles’ heel of any coating system. This is why a silicone primer is so important for the effectiveness of the paint coating. It creates a dry zone under the paint and thus prevents substances such as alkalis and salts within the construction material from damaging the facade.
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14. Why is it advisable to coat exterior insulation and finish systems (EIFS) with silicone resin emulsion paints?

EIFS, in particular, benefit from all the special properties of silicone resin emulsion paints: water repellency, water-vapor permeability, dirt repellency, stress-free drying, easy processing, etc.
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15. Is silicone resin emulsion paint readily overpaintable?

All coatings containing a wetting agent (emulsion paints, silicone resin emulsion paints) will adhere to silicone resin emulsion paints, but silicate paints and whitewash will not.
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16. Must an old coating of silicone resin emulsion paint be stripped off before a new coating can be applied?

No (see also Question 10 ). You merely need to clean the facade, remove any loose particles and, ideally, treat it with a silicone primer. This also applies to old mineral coatings (silicate and organosilicate paints and whitewash).
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17. Why is it worthwhile to use silicone resin emulsion paint rather than cheaper alternatives?

The quality of a facade paint is measured by the length of time it protects the facade from external influences and keeps it looking perfect. Slicone resin emulsion paints are unparalleled in these respects, which makes them much more economical in the long term.