Tile roofs have become increasingly common in Finland over the past 30 years. While tile roofs are known for their durability and quietness, their protective coating typically lasts only about 20 years. After this period, the tiles are prone to accumulating moss, which can lead to frost damage in winter and even cause the tiles to crack. Many Finnish tile roofs are now at an age where rain alone is no longer sufficient to keep them clean, leading to moss growth. As a result, roofs have started to be cleaned with strong chemicals. Although safety data sheets warn about the toxicity of these substances and the dangers of them reaching water bodies, the reality often differs. Roofs are typically pressure washed, and then chemicals are applied and left to be washed away by rain. This practice leads to the chemicals eventually ending up in waterways, causing significant harm, especially in small streams where the water flow is low and the chemicals do not dilute properly. The smaller the water flow, the greater the harm.
In Finland, roof cleaning companies have advertised their cleaning agents as biodegradable and even environmentally friendly. Nearly all chemicals are biodegradable, but this claim alone doesn’t guarantee safety. The environmental friendliness of chemical roof cleaning is highly questionable and, in many cases, a misleading claim. Safety data sheets instruct users to avoid the release of these substances into water bodies at all costs. While some may claim that the chemicals evaporate into the air after application, the truth is that they are eventually washed into nearby water systems by rain, causing ecological and fisheries damage, especially in the smallest streams.
One commonly used moss removal product in Finland is Novo Clean from the Danish company Nowocoat Industrial A/S, as well as BioComb from Sokeva Oy. In Sweden, a popular product is Grön-fri. The homeowners’ association in Sweden recommends cleaning tile roofs every two years, whereas in Finland, it is recommended to clean them every 5-10 years. Chemical roof cleanings are performed not only on tile roofs but also on metal roofs. It is crucial to be aware of the risks associated with the use of these roof-cleaning chemicals, especially in areas where homes are located near small streams.
Although environmental protection laws aim to prevent environmental contamination and fish deaths, the consequences can still be severe if the risks are not recognized or understood. In the smallest trout spawning streams, there are often only first-year fry, which are typically 3-6 centimeters in size and easily go unnoticed. In recent years, mysterious fry disappearances have been observed in such streams in Finland, and monitoring led us to identify this risk. Only afterward did we notice the notice from the Finnish Safety and Chemicals Agency (Tukes), which strongly recommends cleaning roofs mechanically without the use of chemical agents. If chemical agents are used, it is crucial to exercise extreme caution and minimize the runoff into waterways—easier said than done.
All roof cleaning products are biocidal preparations that can only contain active substances approved within the EU. However, the health and environmental risks associated with these substances are still under evaluation. In the future, the marketing of such products in Finland will require approval from the Finnish Safety and Chemicals Agency (Tukes). Currently, companies selling these products are responsible for ensuring that they contain only approved active substances and that their use, according to the instructions, is safe.
When marketing products that contain hazardous or harmful substances, the properties of these substances must be accurately presented. The Chemicals Act prohibits the use of misleading or incorrect safety claims in advertising. However, the Finnish Safety and Chemicals Agency has found that products containing harmful ingredients have been incorrectly advertised as ”non-toxic to humans and animals,” for example.
Text & photo: Henrik Kettunen, doctoral researcher
Links:
https://www.villaagarna.se/radgivning-och-tips/utomhus/tak/mossa-pa-tak/