Physics instead of chemistry: facade care without washable biocides

Blog Fassadenpflege

Builders and owners attach great importance to the facade of their properties. After all, it is not just a means to an end, but the calling card of the house. Who wants to constantly look at algae growth, lichen and gray haze? But on modern, contemporary insulated facades, these undesirable microorganisms are particularly keen to spread. From time to time, comprehensive facade care is therefore necessary. Builders want an economical solution that remains nice over the long term. In addition, many owners increasingly attach importance to eco-friendly and health-friendly materials.

Saint-Gobain Weber’s AquaBalance technology optimally meets these requirements. Its hydrophilic principle of action naturally protects the facade from algae and fungi – without washable biocides. In this article you will learn everything about the unpopular facade vegetation as well as about hydrophilic top coat renders and renovation paints that help you to get to grips with this problem – without polluting the environment.

Chapter overview

  1. Algae and fungi on the facade - a growing problem
  2. How to protect your new building
  3. Simple renovation for existing buildings
  4. Conclusion: there are durable solutions against algae and fungi - even without a chemical mace

1. Algae and fungi on the facade - a growing problem

Facades are the first thing you notice about a building. Whether the property is rendered in classic white, creamy pastel colours or in a trendy colour, such as taupe or anthracite: every carefully-selected shade is distorted by gray-green veils on the facade. Behind the dirty facade is the growth of algae and lichens in combination with settling dirt from the surrounding air. First, the only remedy: a facade renovation.

Where do the unwanted stains come from?

The causes of the annoying micro-organisms are quickly found: algae as well as fungi, lichen and bacteria are present in the ambient air and naturally settle on the facade. They adhere to the surface without penetrating it and algae feel particularly well in damp places. They need nutrients to think and to grow. Damp facades with nutrient-rich air are a paradise for them. This is also the key to combating the annoying squatters: dryness and warmth. Algae and fungi avoid areas with long, strong sunlight, so they are rarely found on the south side of buildings.

Therefore, you should eliminate algae growth

An unbalanced moisture balance is the perfect breeding ground for proliferating algae. As a rule, algae growth is not directly harmful to health. Even the render is not affected by the presence of algae alone, as they settle only on the top layer of the facade. The vegetation is still unsightly, but above all it provides an ideal breeding ground for fungi. Fungi infestation, in turn, can grow into a health hazard depending on the fungal stem, because fungal spores also migrate into the interior of the building. Therefore, consider algae and fungi infestation as an early warning system for moisture, which can cause massive damage to the building structure.

2. How to protect your new building

Homeowners are proud of their property, but with conventional renders and colours, the facade remains attractive for only a few years. After a short time, the facade loses its radiance, and gray veils form in some places. Especially on corners, edges and the socket part of the facade, gray-green spots appear increasingly, which become larger with time. If you already consider a few things when building your property, you can save yourself this worry later.

Location: does country air make facades green?

Not every house is equally affected by algae, and an imbalanced moisture balance on the facade is decisive for their growth. In principle, the risk of living micro-organisms in areas with a lot of fog and precipitation is higher than in dry regions. The proximity to trees and shrubs as well as to standing or flowing waters makes it likely that more regular facade care or a facade renovation must be carried out. However, these factors occur both in rural regions and in cities - so country air alone does not make facades green. Apart from location factors, there are other causes that facilitate algae growth:

  • No or too small roof projections
  • Leaky connections or rainwater drainage
  • Insulation with a thermal insulation composite system
  • Insufficient waterproofing of the house
  • Diffusion behaviour of facade coating

Material selection: top coat renders with hydrophilic active principle

A safe detail formation, for example in roof and parapet borders, reduces the risk of algae infestation, but does not provide safe protection on its own. For a long time, therefore, the addition of biocides in top coat renders was considered the most effective method of killing algae and fungi. However, this has two serious disadvantages: render surfaces with biocidal film preservation demonstrably lose their protective effect after a few years. In addition, the water-soluble biocides are washed out of the facade by the rain over time and thus reach the surrounding soil and groundwater.

The AquaBalance renders of Saint-Gobain Weber combat the growth not chemically, but physically. The facade renders are hydrophilic, which means that they temporarily absorb moisture and after a short time release it back into the air. Dew or raindrops on the facade evaporate particularly quickly and the moisture balance management of the property remains equilibrated.

Dry facades provide no breeding ground for algae and fungi: The hydrophilic principle of action ensures effective, eco-friendly and lasting protection against algae and fungi. Especially in new buildings, owners can already largely prevent the formation of algae and fungi by choosing a suitable top coat render.

3. Simple renovation for existing buildings

When buying an existing property, the facade should always be checked carefully to detect algae infestation as early as possible. If the infestation is already advanced, a new coat of paint is not enough for facade renovation. Where a strong fungal infestation is detected, the facade is often already damaged by moisture. In this case, the facade render must be removed and renewed. For cases with less severe infestation, a renovation paint with a likewise hydrophilic facade paint is sufficient: weber.ton reno AquaBalance which is friendly to environmentally and weather-resistant and also works on the basis of the hydrophilic principle of the AquaBalance technology. The paint should be applied in at least two full-surface layers. There should be at least 12 hours of drying time between the intermediate and the top coat.

4. Conclusion: there are durable solutions against algae and fungi - even without a chemical mace

More and more people are paying attention to a low-emission, healthy environment. Authorities and public institutions are also becoming increasingly aware of issues relating to environmental protection. Some municipalities in Germany already link the allocation of subsidies to the use of biocide-free products.

Beyond state requirements, environmentally friendly renders and paints contribute to an ecological footprint of new and existing buildings. For comparison, a bucket of conventional facade render contains up to 80 grams of biocides. Scientists assume that in Germany alone up to 450 tons of harmful biocides are released into the ground and thus into groundwater every year. These damage water organisms; some substances are suspected to be mutagenic or carcinogenic for humans.

Over 10 years ago, Saint-Gobain Weber developed the renders with the natural principle of action against the formation of algae and fungi. Since then, more than 15 million square meters of facade have been treated with AquaBalance renders. Saint-Gobain Weber has already received several awards for this far-reaching innovation. Among them the "Bundespreis ecodesign" (2012), the "Innovationspreis Klima und Umwelt" (2013) and the "Greentec Award" in the category "Bauen und Leben" (2016). Since 2020, suitable renovation paint for existing buildings has also been available.

All the benefits of AquaBalance technology at a glance:

  • Effective and long-lasting algae protection for new buildings
  • Suitable for facade renovation of existing buildings
  • Easily applicable on old renders and paints
  • Environmentally friendly: free of harmful, biocidal film preservation
  • Significant extension of time intervals between facade renovations
  • Dirt-repellent, solvent-free and weather-resistant
  • Open diffusion behaviour: permeable to water vapour and hydrophilic

Further information on Weber’s unique AquaBalance technology can be found here.