Additional heat in Dutch cities could be effectively reduced by reflective roofs

News - 07 December 2017 - Communication

Changing the colour of roofing tiles could considerably reduce extreme temperatures in Dutch cities. Introducing this idea is Leyre Echevarría Icaza, who will be awarded her PhD at TU Delft for her work on this subject on Friday, 8 December 2017.

Heat island

It is usually warmer in cities than in the surrounding countryside, primarily because buildings retain more heat. This is called the Urban Heat Island (UHI) effect. The phenomenon could have far-reaching consequences, particularly in cases of extreme heat. During the 2006 heatwave in the Netherlands, for example, the UHI effect resulted in an increase in recorded deaths.

Satellite imagery

During her PhD research, Leyre Echevarría Icaza investigated the most effective means of mitigating the UHI effect in Dutch cities. She argues in favour of using satellite images to chart and analyse UHI effects. ‘Alongside facilitating analysis of the heat island phenomenon in Dutch neighbourhoods, cities and regions, satellite imagery can also be used to help make recommendations. The analyses and recommendations are sufficiently accurate to be efficient and are also compatible with other urban planning considerations.’

Improving albedo

Echevarría Icaza investigated city centres including Delft, Leiden, Gouda, Utrecht and Den Bosch at neighbourhood level. These centres are characterised by their canals, red ceramic roofing tiles and stone paving. There are various ways of mitigating the UHI effect in these areas, but what complicates matters is that these city centres are full of listed buildings. The most straightforward measure to implement is improving the reflection (albedo) of roofs – by changing the colour of the roofing tiles, for example.

Orange tiles

‘At the end of their life cycle, the existing roofing tiles could be replaced by tiles in colours that reflect more solar radiation. Traditional roofing tiles have an albedo rating of between 18 and 22%, while certain orange tiles offer reflection of approximately 50%.

The effective improvement of all flat and sloping roofs could help to reduce temperatures in certain areas of the city by 1.4 to 3 degrees. This therefore appears to be an efficient means of reducing UHI effects in Dutch cities.’

More information

8 december 2017, vanaf 12:30 , Aula TU Delft
Promotion Ir. L. Echevarria Icaza, Urban and regional heat island adaption measures in the Netherlands
Promotors: A.A.J.F. van den Dobbelsteen en F.D. van der Hoeven (Bouwkunde)
Contact Leyre Echevarria Icaza:,
Frank van der Hoeven:, +31 15 2788462
Press Officer TU Delft: Sharita Balgobind,, 015 2781588