The heat island in The Hague doesn’t just cool off

You feel the few degrees more immediately. Walk from The Hague Central, where it’s always cold and shaded by the ministerial towers, along the tree-lined canal to the south. Around the corner, onto Hillebrant Jacobsplein.

Large mansions and a tower surrounding two ponds. In the large pond there are six listlessly spouting fountains, creating a clear water circle in the thick green algae layer. The square consists of a lot of stone and little shade. On summer days like today it can get a few degrees warmer here than elsewhere in The Hague. And at night it cools down considerably less.

But it is already a bit cooler on Hillebrant Jacobsplein than it was a few years ago. A plant border has been created around the small pond, a small birch has been replaced by three lime trees. Façade gardens have been laid out in front of thirty houses, and façade plants are crawling against some walls. “It helps on a small scale,” says resident Otto Thors. “There is more shade.”

In 2012, TNO presented research that showed that The Hague had the largest heat islands in the Netherlands: petrified places where road surfaces, facades and roofs absorb heat, retain it and radiate it to the environment. Residents on this square in the Rivierenbuurt set up the website heat-eilanden.nl to draw attention to heat stress.

From later research by TU Delft it turned out that the heat in The Hague was no worse than in the other cities, but the seriousness of those high temperatures had already penetrated administratively in the court city. Because in a city that already has the most densely populated neighborhoods in the country, where additional buildings have to be built for a growing and aging population, the inhabitants are vulnerable during hot summers. There were already summers with more deaths than the average in the Netherlands.

Also read: Every city has its heat islands

A number of solutions were also proposed in the 2018 TU Delft research: less bitumen flat roofs that retain heat, while renovating old homes not only pay attention to retaining heat in winter, but also to the keep cool in summer. And above all: less stone and more green.

Since then, the municipality has distributed a thousand trees every year, the ’tiling tile’ championship has been held, and there are subsidies for greening roofs. The 2018 and 2019 coalition agreements promised “to tackle the ten most urbanized areas in every neighborhood” and a “square approach”, in which residents could redesign and green their neighborhood squares together with municipalities.

Trees and flower boxes

It depends on who you ask whether it also had an effect. The municipality points to all kinds of initiatives: trees have been planted throughout the city and squares have been redesigned. 120,000 tiles were replaced with greenery, and 130,000 square meters of roof will be greened in 2020 – the target this year is 260,000 square meters. A Cruyff field has been given an infiltration crate (underground water storage) under the concrete benches, the petrified square near the Julianakerk in Transvaal now has a bed in the middle with butterfly bushes.

These initiatives are often initiated or tackled by residents themselves. Such as on Hillebrant Jacobsplein. The square, which won urban renewal awards in 2007, was simply too hot, says resident Otto Thors.

“You could see trees in the architect’s drawing, but only the buildings were completed. Trees on top of the parking deck were not possible, the bearing capacity was not strong enough. In fact, as a neighborhood we are now repairing problems in public space that the municipality did not notice during construction twelve years ago.”

They have done a lot themselves: the facade gardens, the beds around trees. They cut through 24 centimeters of reinforced concrete to accommodate plants. Not everything is possible: Thors says that the water in the large pond can be “twenty to thirty degrees”. But it is too shallow to grow plants. “So we’re looking forward to a green endive soup.”

He talks about the neighborhood cooperative GroenDruk, which they have set up – to mobilize residents and “keep the pressure on” in the district. Because although “administratively everyone thinks greening is important, the pace at which it is being achieved is slow,” he says. “We have enough neighbors here with perseverance. After hearing ‘it can’t’ ten times, most others would say ‘never mind’.”

“It really can be better,” says PvdA councilor Janneke Holman about greening the city. She tells about the tree mirrors (beds around trees) that residents of The Hague build and then are ‘mown’ by the parks service, about someone who was fined for a facade garden against an electricity box. And about a playground where two municipal departments and a housing corporation pointed to each other: “The residents see a dilapidated square.”

Holman sees that all kinds of residents’ initiatives are emerging in the more affluent neighbourhoods. “The most urbanized neighborhoods – Transvaal and Schilderswijk – are also home to the most vulnerable residents. That is where an impulse is needed.” 10,000 euros has just been made available for the Transvaal to plant trees there.

The Party for the Animals also sees ‘restraint’ in the approach to squares. “The idea is now often: put down a tree somewhere and then it is ready. A tree equals ten air conditioners, but only in a certain environment. If it is tiled, the water will evaporate at the roots,” says council member Robin Smit.

Improvements are ‘very slow’

The big question is whether The Hague has become cooler. It is difficult to see whether the measures have had an effect, says Frank van der Hoeven of TU Delft, who conducted the heat study in 2018. “The KNMI measures outside the city. We measured by having residents measure themselves on their balconies. That made them aware, but you get huge differences from place to place. It matters whether someone measures on the north or south side, on the ground floor or higher.”

He expects the improvements to be “very slow”. “A tree here and there. It takes ten to twenty years before you have a crown such that the tree provides good shade.”

In addition, says Van der Hoeven, “most people mainly live in buildings. There is often air conditioning in commercial buildings. Vulnerable people, children up to 3 years old and people over seventy, are at home.” And not everyone has “a mature tree for the home that has good foliage,” nor a home that is insulated.

Using the data from 12,000 smart Toon energy meters in homes in The Hague (which were received aggregated from producer Quby to protect the privacy of residents), he was able to see what happens indoors during a heat wave. “What you see is that the temperature increases towards the center of the city, that the proximity of the Zuiderpark and the Haagse Bos seem to help little, and that the North Sea brings coolness.” He saw peaks of up to 40 degrees in the warm summers of 2018 and 2019.

“It’s nice if the temperature on the street is comfortable or if a small park is not too paved,” says Van der Hoeven. “But that is not the place where you look for cooling in a week like now.”

The municipality of The Hague has all independently living people over 75 sent a letter with heat tips. When the heat lasts longer, “cooling centers” open: religious buildings, libraries, and government offices.