Self-cleaning paints and renders – a bright idea?


By Nikolaos Mantelis, product manager at building materials manufacturer Baumit

SELF-cleaning paints and renders offer a sustainable, reliable method of maintaining a building’s façade without the need for regular and costly renovation. 

As well as reducing long-term expenditure, products which require water or natural elements such as daylight, rain or air moisture to cleanse surfaces are kinder to the environment. Self-cleaning solutions eliminate the need for aggressive sanitary regimes, which often contain harmful toxins – a fact worth remembering, as the government struggles to make good its pledge to reduce UK CO2 emissions by a minimum 80% from 1990 levels by 2050. 

The two main self-cleaning topcoat systems currently available require different climatic conditions to trigger the cleansing process. One uses direct rain or water contact, allowing dirt contained within a droplet to simply roll of the surface. This system is fine in principle, but slightly flawed in practice. The electrostatic properties of the molecules contained within the topcoat means if a hand or other object such as a ball comes into contact with the surface, a dirty print will be left behind. Nanopor is different…

Nanopor systems require nothing more than sunlight, humidity and wind to provide a uniform, dirt-free surface. 

A special photocatalyst additive, which has been developed by Baumit, uses the power of light to activate the self-cleaning effect in its Nanopor range of renders and paints. The ‘Nanopor-effect’ is produced when sunlight activates the photocatalysis additive in the render or paint, affecting the upper-hydrophilic nano layer within the product whilst it dries. During the process, dirt is decomposed and lifted from the surface by air movement. Any remaining particles are removed by rain and evaporation of absorbed dampness. 

For a simpler explanation of the ‘Nanopor-effect’; when a drop of water falls on a normal hydrophobic render surface, it will appear as a ‘ball’ of water. A drop of water when dropped onto Baumit NanoporTop loses its surface tension. During evaporation the moisture releases dirt particles, resulting in a dry, clean and beautiful façade. 


 Thorough cleansing   

Because Nanopor doesn’t depend on direct contact with water to trigger the self-cleaning process, areas of a building not exposed to rain – such as those beneath the eaves – are also thoroughly cleansed. This enables a consistent, clean performance across the entire building and eliminates issues such as streaking or dark patches forming where water was unable to connect with the façade.

The photokat process is particularly effective against fungi or mould in a façade. It’s also superb for removing smoke or dust particles. Again, it’s worth making the point that the innovative Nanotechnology in renders and paints reduces the need for a building’s renovation, making it a cost-effective and environmentally-friendly alternative to other exterior coatings. 

As with most self-cleaning exterior finishes, Baumit NanoporTop, a ready-to-use dirt and pollution-repellent render, can be hand or machine-applied. It features unique nano-crystalline and non-organic additives which result in significant surface reduction of pollution compared to other coatings, leaving a building protected and looking clean and bright. The microscopically smooth surface of Baumit Nanopor render and paint offers a façade a unique protective barrier against pollution, as dirt particles have nothing to cling onto. 

Breathe easier 

It is estimated poorly-insulated homes account for 25% of emissions released in the UK, hence the need for a focus on improving the thermal performance of our new and existing properties. Airtight buildings are important, but they must also be able to breathe. Think about what goes on inside of a house – washing, cooking, bathing…even breathing. All that moisture has to go somewhere – ideally out of the building. However, with some topcoats and renders, it’s like placing a plastic bag over a home’s exterior. Sure, the building’s better-insulated, but it’s also trapping escaping moisture which can result in damp and mould growth, and lead to health issues for occupants. 

Baumit’s topcoat and colour product range contains a “nanoporous” structure, which allows buildings to breathe – keeping them warm in winter and comfortably cool in summer whilst eliminating the potential for moisture retention and damp.

The development of self-cleaning top coats and renders has given a whole new lease of life to building facades. By focusing as much care and attention to the array of available technically-advanced, high-performance materials we apply to the outside of a building, will help ensure a more comfortable and healthy environment for those on the inside.