-
The issue with conventional exterior paint is the soil of the facade becomes increasingly visible over time. A super-hydrophobic coating has a highly water-repellent surface, where water droplets flow off immediately, picking up dirt and leaving the facade dry and attractive. Mechanical action, such as abrasions, hail, swelling, and building movement. For example, people come and go through the front doors and may congregate out front, resting against the side of the building. Ladders leaning against the outside of the building or extreme weather such as hail can also damage the structure or cause abrasions which compromise any coating applied to the exterior cladding.
- Air pollution, including organics such as nitrogen oxides (NO) and mineral materials such as dust. In California, forest fires blow smoke and soot across the environment. In rural areas, fertilizers used on farms release nitrates into the air. In cities, hydrocarbon soot from diesel exhaust and jet exhaust leaves behind a sticky black residue. These pollutants can deteriorate the coatings and appearance of the facade.
- Biological organisms, such as mildew or fungal growth. In coastal regions, algae is common on the exteriors of a building, creating an unappealing green appearance and decreasing the effectiveness of the coating. In damp, humid climates, fungal growth can propagate and bond to coatings, making it difficult to remove and leaving a deposit on the surface of the coating.
- Bulk water includes rain, dew, snow, humidity, and other moisture and water vapor. The coating is the first face to the elements and requires effective, reliable water resistance. However, a traditional water-based coating can soften when exposed to bulk water. The softer coatings become tacky and attract dirt which does not wash away easily.
- Temperature and light effects due to climate and ultraviolet (UV) rays. Similar to a person’s skin burning in the hot sun, temperature and light can also degrade coatings on the exterior of buildings, making them fade after years of exposure. Moving North to South, the amount of UV exposure increases significantly.
Architects, designers, and specifiers can select from a wide variety of coatings to help protect a building’s exterior wall.
Acrylic coatings offer a variety of protective characteristics including durability, fade resistance, and resistance to cracking, peeling, and chipping while bridging hairline cracks. They extend the lifetime of a structure’s appearance and protect it from the elements. Applicable in new construction or a recoating situation, such coatings provide a variety of aesthetic options and preserve the value of buildings by serving as a breathable, durable, attractive layer of protection.
Hydrophobic coatings are acrylic coatings which repel water. This enables faster drying of the surface, reducing the opportunity for mold, mildew, dirt, and other pollutants to grow or stick to the surface. They may be used for new construction or recoating existing buildings, and help the building maintain its aesthetic appeal and perform better against the elements, while lowering maintenance costs and frequency of recoating.
Though hydrophobic coatings offer several performance benefits, to mimic the self-cleaning capabilities of the lotus leaf, coatings must be super-hydrophobic.
The benefits of super-hydrophobicity
Super-hydrophobic materials possess a highly water repellent surface, similar to a lotus leaf. Their microstructure mimics the lotus plant to minimize the contact areas for water and dirt.
Measuring the hydrophobicity of a material requires looking at the contact angle by placing a water droplet on the material’s surface. The advancing angle just as the droplet starts to move is the contact angle.
The higher the contact angle, the higher the hydrophobicity. Higher hydrophobic materials will have less water on the surface and dry faster, leading to improved performance in the critical factors, affecting the performance of the building’s exterior. This includes better freeze-thaw resistance, mildew and weathering resistance, UV protection, dirt collection capabilities, and staining resistance.
No matter which facade solution is selected, whether above-grade concrete, concrete masonry, exterior insulation and finish systems (EIFS), stucco, or previously painted wall surfaces, a coating or finish will be applied for added protection and aesthetics. Hydrophobic coating offers additional armor and long-term value. With these applications in mind, super-hydrophobic coatings enhance building performance in the following ways:
