“Eco-friendly” is not a regulated term in exterior cleaning. Any company can print it, and most do. So it is worth knowing what these treatments actually contain, what the law genuinely requires of them, and which precautions do the real work of protecting a garden — because those are procedures, not adjectives.
An unregulated word
There is no certification scheme that grants an exterior cleaning contractor the right to describe their treatments as eco-safe, and no standard defining what it would mean. In practice the phrase gets used for at least four different things:
- A product that breaks down quickly in the environment.
- A product that is less harmful to aquatic life than the obvious alternative.
- A method that uses less water, or no chemicals at all.
- Nothing whatsoever — marketing copy attached to a standard product.
Those are genuinely different claims, and only the first three are worth anything. Since the words do not distinguish them, the useful questions are about the product and the procedure instead.
What is actually in a moss and algae treatment
Almost all effective roof and render treatments in this trade are biocides: products designed to kill living organisms — moss, algae, lichen, biofilm. That is not a scandal, it is the mechanism. Growth that is only removed mechanically returns quickly, because the spores are already everywhere and an Irish climate is ideal for them.
The families in common use, in broad terms:
- Quaternary ammonium compounds. The workhorse of roof and render treatments. Applied at low pressure and left on the surface to work over weeks, with no rinse-off. Effective, long-acting, and harmful to aquatic life in concentration — which is why the runoff plan matters more than the product choice.
- Sodium hypochlorite — household bleach chemistry, at working strength. Fast and visually dramatic, which makes it popular for before-and-after photographs. It also kills planting on contact, corrodes metal, can bleach fabric and paving, and does much less to prevent regrowth than its immediate effect suggests. Its speed is the reason to be cautious of it, not a recommendation.
- Surfactants and detergents, which help a product wet and cling to a surface rather than run off it. Usually the least concerning component.
The honest summary: a treatment that genuinely prevents regrowth is doing so because it is biocidal. Anything marketed as both completely inert and long-lasting deserves a question about which of the two it actually is.
The rules that do apply
The word “eco” is unregulated. The products are not. Biocidal products are controlled across the EU, and Ireland applies that framework:
- A biocidal product must be authorised for sale and use here, for the specific purpose it is sold for, under the EU Biocidal Products Regulation. An unauthorised product is not a grey area.
- The label is legally binding. Dilution, application method, protective equipment and precautions are conditions of use, not suggestions.
- A safety data sheet exists for every product, and it is a document you can ask for. It states the hazards, the ecological effects and the disposal requirements in plain, if dry, terms.
- Water pollution is a separate matter of law. Letting a biocide reach a watercourse is an offence regardless of whether the product was correctly authorised, and “it went down the drain” is not a defence.
This is the substantive reason to prefer a contractor who will name their product: an authorised biocide used to its label is a controlled activity with a paper trail, and anything else is somebody guessing on your property.
What actually protects the ground underneath
Nearly all the environmental risk on a domestic job is in the runoff rather than in the product, and it is managed by procedure. In rough order of how much difference each makes:
- Know where the drains go. A surface water gully generally discharges to a watercourse; a foul drain goes to treatment. Which one the driveway drains into changes what may be allowed to reach it. On the older parts of Dublin and Cork city the two are often combined, and are not always where you would assume.
- Cover or block gullies during application, and let the first flush go to a contained area rather than straight to the grating.
- Sheet and wet down planting before starting. Wet foliage takes up far less of anything that lands on it, and a physical sheet is worth more than any amount of care with the lance.
- Ponds get covered, without exception. Fish and amphibians are the most sensitive things on a domestic site by a wide margin, and a garden pond has no dilution to fall back on.
- Dilution and dose to the label. Over-dosing does not clean better; it puts more active into the ground for no gain.
- Mind the wind and the neighbours. Spray drift onto a neighbour’s planting, car or washing is the most common complaint on this kind of work. On exposed Atlantic sites — much of Galway — the wind decides whether a treatment can be applied safely on a given day at all.
- Keep pets and children off treated surfaces until the label says otherwise. This is the question most customers actually want answered, and the label answers it.
The genuinely gentler options
There are methods that reduce or remove the chemistry, and they are real — with real trade-offs:
- Hot water alone. Heat kills growth without any biocide. It works, it costs more in fuel and time, and it has little residual effect, so growth returns sooner.
- Steam. Effective on hard surfaces and on delicate stone where pressure is not an option. Slow, and slow means expensive on a large area.
- Mechanical removal only. No chemistry at all. Entirely reasonable if you accept that the moss will be back on a much shorter cycle — see how roof cleaning works for why the treatment stage is what buys the years.
- Lower pressure with more dwell time. Not an alternative to chemistry so much as the way to use less of everything, and it is the basis of soft washing.
- Deal with the cause. The most environmentally sound intervention is the one that does not need repeating. Cutting back the overhanging branch that keeps a patio in permanent shade, or clearing the gutter that keeps a wall wet, reduces how often anything has to be applied at all.
What to ask before work starts
Five questions. Any competent contractor can answer all of them on the phone:
- What product are you using, and can I see the safety data sheet?
- Is it authorised for this use in Ireland?
- What are you doing about my drains, my planting and the pond?
- How long should pets and children stay off the treated surface?
- What happens to the material you remove?
Those questions are worth more than any label on a van. If you would rather ask them of us, the same information applies to roof cleaning and render and house washing, and we will put the answers in writing before anything is scheduled.