Heat in the city

During the so-called research phase, different parties, together with residents, mapped out the heat issues in Nieuwegein, Amersfoort, Utrecht and Veenendaal. The residents took note of the air temperatures in their own residential and work environments three times a day during a hot summer week in August 2012 (heat measurement) and filled in a questionnaire (perception survey). A total of 150 people took part, using the accurate thermometer and measuring protocol they received. The perception survey revealed that 30% of people sometimes suffered from the heat outside, while 47% said that they suffered little from the heat. Inside the home, people suffered from the heat mostly during the night, i.e. in the bedroom. Many people were able to find a cool environment in the immediate vicinity of their house during the day, but 44% of them had to travel more than a kilometre to find such relief from the heat.

During the same summer, Wageningen University & Research Centre conducted an intensive scientific study into the UHI effect in the city of Utrecht. With a carrier tricycle full of equipment, the researchers cycled around the city and took measurements. They also took photographs of the buildings and green vegetation in the surroundings. The measurements provided greater insight into the urban heat island effect, particularly with respect to the effect of green vegetation on the results.

A third component of the research phase was conducted in parallel to the aforementioned measurements: crisscrossing the cities – from one edge to other – several more systematically set-up series of measurements were taken via amateur weather stations that were hung on the houses of volunteers. This research was conducted in Utrecht and Amersfoort. In this series of measurements, the air temperature, air pressure and rainfall were continually measured and, insofar as possible, related to other relevant data (such as wind, particulate matter, and suchlike).

Results

The measurement study showed that the difference in temperature inside and outside the city of Utrecht could be as much as 5 degrees. In the city, too, the temperatures can differ sharply. In Utrecht the urban heat island effect develops on sunny days that have little wind. At locations with a lot of brickwork and little vegetation, the temperature doesn’t drop much at night. The city of Utrecht, in fact, radiates so much heat that when the wind is blowing in a certain direction it affects the temperature in De Bilt.

The Roerplein in Utrecht’s Rivieren neighbourhood

The Roerplein was a small, paved square with small pitiful-looking trees and a couple of dirty benches. The residents took the initiative of introducing plants to the district. By participating in the project, neighbourhood residents got involved with the square and created a management group. Working with children from a school nearby and neighbourhood residents, a landscape architect drew up a landscape plan. The plan was then approved by the residents and the municipality of Utrecht. Implementation of the landscape plan began in the spring of 2014.

Lessons learned

The Heat in the City project has been successful both in terms of content and communication. The combination of factual and perception studies seemed to work well. It inspired involvement and produced insight. For many people living in brick-and-pavement urban districts, the summer is occasionally very hot – too hot. Too much brick, too much asphalt, too little vegetation, houses that were not designed for high temperatures: everyone occasionally experiences the urban heat island effect.

This project makes it clear that action needs to be taken in the Netherlands. Other projects in other urban areas in the Netherlands are also making this clear, just as the New Urban Developments & Restructuring Delta Programme, the Climate-Resilient City Manifesto, etc. Various municipalities in the Netherlands, including Utrecht, are reflecting on this issue and are beginning to develop policies to create a climate-resilient city and, especially, to combat the summer heat.

Such a project could easily be repeated somewhere else in the Netherlands in a similar manner. Residents like to be involved in their neighbourhood. Let people take the measurements: although the measurement data of residents is not perhaps 100% “scientifically accurate”, it does provide a good picture, and involving residents increases their awareness. The principle that applies to energy-saving efforts also extends to temperature perception: knowledge is power. It prompts people to take measures such as shutting windows and doors during the hottest times of the day or sitting at rest in the shade. Yet for urban designers, urban planners and municipal authorities, too, the urban heat island effect has gradually become an identifiable phenomenon that must be taken into consideration. This means more green vegetation and water gardens. But it especially means no longer building large squares containing nothing but paving.

Contact person

Marcel Blom
Natuur en milieu Utrecht
marcel.blom@nmu.nl