The use of rainwater can be a practical way of reducing a building’s running costs. Although it is still not a widespread solution in Poland, it allows for a significant reduction in water consumption from the mains – in office buildings by as much as approx. 40 per cent of annual consumption. However, proper design, metering, regular servicing and tailoring the system to the property’s actual needs are crucial.
The importance of rainwater retention, recovery and utilisation systems is growing as climatic conditions change. According to the latest report from the World Meteorological Organisation (WMO), ‘Global Annual to Decadal Climate Update 2026–2035’, the years 2026–2030 may be among the warmest on record. Global temperatures are expected to be between 1.3°C and 1.9°C higher than the pre-industrial average during this period, and there is a 91 per cent probability that at least one year will exceed the 1.5°C threshold.
Every additional fraction of a degree increases the risk of heatwaves, droughts, heavy rainfall and other extreme weather events. For industrial buildings, this means the need for a more flexible approach to water management. Longer periods without rainfall increase the pressure to reduce water abstraction from the mains supply, whilst heavy downpours require more effective retention, storage and utilisation of rainwater when it is available. In this context, rainwater becomes not only an environmental resource, but also a factor in managing costs, technical infrastructure and the operational resilience of the building.
In industrial facilities, rainwater can support selected technical processes, such as cooling, provided that technological, sanitary and design requirements allow for this. In suitably selected facilities, such solutions can reduce water abstraction from the mains by up to approximately 40 per cent of annual consumption. We have had such experiences with office buildings. However, it is crucial to analyse in advance where drinking water is essential and where water with different parameters can be safely used. The assessment should also cover the technical capabilities relating to the collection, filtration, storage and distribution of rainwater. Only on this basis can it be reliably determined whether the implementation of such a system will be technically and economically viable – emphasises Dorota Włodarczyk-Strugalska, project group manager at SPIE Building Solutions.
Water intended for consumption remains essential at tap points, in kitchens, staff facilities and in systems requiring a specific quality. However, it does not need to supply every technical or operational process.
From consumption analysis to investment decision
The potential for rainwater utilisation depends on the parameters of the specific building. Factors such as roof area, local rainfall totals, available space for storage tanks, the layout of the system and the actual demand for water for non-potable uses are all significant. The situation is different in an office block with a large roof area and extensive green spaces, different again in a service facility in a densely built-up area, and yet different in an industrial plant.
In practice, the decision to invest should be preceded by a technical and economic assessment. The property manager should compare the potential volume of reclaimed water with the cost of installing the system, fitting metering equipment, maintenance and any necessary modification of the existing infrastructure. In new developments, it is easier to incorporate such systems at the design stage. They are also possible in older buildings, but usually require more extensive work on the existing installations.
Water quality is also important. Rainwater should not be regarded as ‘inherently clean’ water. Its parameters depend on the collection site, the type of surface from which it runs off, weather conditions and the method of storage. Water collected from clean, flat roofs with metal cladding, channelled via a guttering system fitted with filters and stored in watertight tanks, preferably in a shaded location, usually has the best parameters. Water intended for watering greenery will have different requirements to that used for flushing toilets, and yet others for water used in technical processes – adds Dorota Włodarczyk-Strugalska.
The best results are achieved with solutions tailored to the building’s function, implemented alongside consumption monitoring and measures to minimise wastage. In logistics and office buildings, rainwater can be stored and used, amongst other things, for watering green spaces, flushing toilets or – provided the relevant requirements are met – for fire-fighting purposes. In industrial facilities, the range of applications can be even broader and include selected technological processes, such as concrete production, cooling units or supplying cooling towers. In this model, rainwater is not an additional eco-friendly system, but an integral part of the building’s comprehensive water management.
Savings for the building, benefits for the city
Office blocks, service facilities and commercial buildings are often situated in dense urban areas, where a high proportion of hard surfaces limits natural water infiltration. In such conditions, rainwater retention and utilisation at property level are important not only for the water consumption balance within the building itself, but also for its surroundings.
Systems that retain or slow down the runoff of rainwater can reduce the volume of rainwater entering the sewerage system in a single event during heavy rainfall. This reduces the risk of overloading urban infrastructure and causing localised flooding. At the same time, water retained on the property can be reused, for example, for watering greenery, flushing toilets or specific technical processes.
Such solutions support more sustainable water management: they reduce pressure on drinking water resources, increase water retention and help mitigate the effects of extreme weather events. For building owners, they mean better control over utility consumption, greater operational resilience and the opportunity to reduce some operating costs.
Rainwater can reduce water abstraction from the mains supply and support environmental objectives, but only if it forms part of a broader water management strategy for the building. Key factors include: minimising wastage, metering the most important circuits, regularly analysing consumption and ensuring the system is properly maintained – points out Dorota Włodarczyk-Strugalska.
Although the use of rainwater is not yet standard practice in Poland, its potential for savings and its importance for the efficient maintenance of buildings will become increasingly difficult to ignore. It will be crucial to plan the system well, select its scale appropriately to the building’s needs, and carry out a cost and payback period analysis prior to the investment. In such cases, rainwater harvesting can bring measurable financial and environmental benefits, whilst also becoming an important element of effective resource management within the building.
