A practical approach towards designing heat resilient cities

Since January 2020, heat stress is officially part of policy and design of public space in The Netherlands. Nevertheless, how to design in a heat resilient way is still open for interpretation. Municipalities struggle with design rules and regulations that help to make cities heat resilient. Together with over 45 municipalities the AUAS developed and tested three design guidelines for heat resilient urban spaces. The first two guidelines focus on creating enough cool spaces locally with a comfortable temperature during the day. The third guideline aims to lower the air temperature throughout the city.
The first guideline, distance to a cool space, states that every home is within 300 meters of an attractive, cool place in the outdoor area. This guideline helps in the search for strategic locations that function as an attractive, cool place to stay and that are within walking distance for residents of the neighbourhood. It is in line with the guidelines of the WHO (2016), recommending a maximum walking distance of 300 meters. This distance can be easily walked within five minutes, even for elderly. A location is considered suitable when it is sufficiently cool, has seating in the shade and is designed as an attractive place to stay.
The second guideline, shade on walking areas, directs at a minimum of 40% shade on important walking routes at the hottest time of the day, to reduce the perceived temperature . This guideline focuses on essential slow-traffic routes, so they remain comfortable during hot days. It is important that the shadow is well distributed over the walking route.
The third guideline, percentage of green, ensures that there is sufficient green space in neighbourhoods. Greenery cools the air: an increase in vegetation cover by 10 percentage points lowers the air temperature by approximately 0.5°C (Steeneveld et al., 2011). The guideline expresses the amount of green space required in a lower limit and a target value differentiated per neighbourhood type. Values have been chosen on the basis of an analysis of the current green in all neighborhoods of four cities. For example, historical city centers have 16% of green on average. This we defined as the lower limit. Whereas, the examples show a potential of 32% of green (average + standard deviation). This we defined as the target value.
The three design guidelines are developed in such a way that you can easily check whether spatial plans meet the objectives for a heat-resilient outdoor space. Municipalities, provinces, designers and developers already use and implement the guidelines in their regulation and everyday practice. In the paper we will explain how the guidelines are being implemented and what further actions are needed.