Global warming is impacting our rainfall patterns. “It is crucial that we manage rainwater wisely,” says Bart Dufour, Senior Project Developer at Antonissen. “Since 3 October 2023, the new regional rainwater regulation requires Flemish people to install larger rainwater tanks and use the water they harvest for domestic applications.” The rules are not entirely new. Regulations from 2004 and 2013 also already enacted rules in terms of the storage, reuse and infiltration of rainwater. “This regulation tightens and expands the previous regulations. New-build homes and total renovations, as well as smaller redevelopment and refurbishment projects must now also comply with the stricter conditions. Which makes perfect sense. If we want to ensure that people can continue to live in Flanders in the long term, everyone needs to make a concerted effort.”
Until recently, a 5,000-litre rainwater tank was sufficient in newbuild and renovation projects. Today, this is the bare minimum. Larger rainwater tanks are one of the most important pillars of the new rainwater regulation. “Depending on the area of your roof, your tank should have a capacity of 5,000, 7,500 or 10,000 litres.” Rainwater reuse is also becoming even more important. “In 2004, one tap was enough, usually an outdoor tap for the garden. In 2013, rainwater tanks needed to preferably also be connected to a toilet. Now, the law states that rainwater tanks must be connected to the toilet, a garden tap, as well as the washing machine. Every drop that is harvested, reused and thus does not flow into the sewer counts.
Harvesting rainwater is one thing, but to prevent waterlogging, the soil must also be able to retain more water. This prevents sewers from overflowing during extreme rainfall. Tighter rules for building in flood-prone areas will also help prevent this. “The building permit application will have to clearly prove that the project will not have a negative effect on the local water system. A certified expert will prepare a science-based report (such as a SIRIO report) showing how the impact on sewerage is reduced. Water channels or above-ground buffer zones that allow water to penetrate slowly into the soil before overflowing into the local sewer system are also worth considering. In hot periods, the water evaporates, lowering temperatures locally and preventing heat islands. A win-win solution.”
Regulations for green roofs are also becoming stricter. “Green roofs can retain about 50% of all rainwater, releasing it back into the atmosphere. This helps cool down the surroundings, in addition to relieving the burden on the sewer system. Under the new rainwater regulations, runoff from green roofs may no longer be discharged directly into the sewer system. It must be buffered or discharged into the soil as much as possible. Above-ground infiltration systems are preferred where this is feasible. In large construction projects especially, keeping underground pipes free of mud and silt requires considerable maintenance. Water channels are an interesting solution here and tie in perfectly with the Flemish climate adaptation plan. This advocates ‘green-blue infrastructures’, where rainwater is harvested in open water features, embedded in greenery. This approach also has aesthetic benefits. “The result is a lovely experience garden, with greenery and water features. In winter, you may even be able to skate on the water, if you’re lucky.”
“Everyone has a part to play in creating a liveable climate. Want to invest in real estate? Choose a climate-neutral building. Harnessing free geothermal, wind or sun energy is now widely accepted as the way forward. However, making smarter use of rainwater is an important next step to arm ourselves against extreme weather conditions. Antonissen's newbuild apartments already meet the climate objectives for 2050. That way, you are fully prepared for the future, giving you a competitive edge in the current property market.”
Do you have questions about the new rainwater regulations or want more information about our developments? Our experts are happy to provide personal advice. Contact us.
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