What are thermal walks?

As developed at the University of Applied Sciences Amsterdam, "A thermal walk is a research method that is used to map out the heat measured and perceived in a particular area, and to obtain answers to questions such as: how heat-proof is a particular walking route in the city, a shopping street, a residential area, the area around a train station, or a market square? A thermal walk maps out which planning layouts are hottest, coolest, most pleasant, and most unpleasant. One of the determining factors is the perceived temperature. Is a location situated in direct sunlight or is it shaded? In addition to air temperature and perceived temperature, the thermal walk considers thermal perception, i.e., how is a particular location perceived in terms of heat? The psychological effect is another important factor in heat-proof spatial planning."

What this means in practice is that a researcher team uses both sensors and participants' experience to determine how heat is experienced in different areas. These results can be used to determine the performance of urban green infrastructure in terms of reducing the urban heat island effect. For the sensor part, two devices are used that register temperature, humidity, wind speed and direction, and importantly, the Wet Bulb Globe Temperature. The device in question we apply is the Kestrel 5400 heat stress tracker. 

 

For participants a questionnaire is held at each location to be tested. Questions relate to topics such as clothing worn, experienced comfort level, and desired changes in environment. At the same time, the sensors calibrate to each environment which takes some 10-15 minutes. If locations are within 2 km, up to 5 locations can be tested in an hour, making thermal walks a practically effective method for measuring the performance of urban green infrastructure. For warm days, the practice is now well established. It is of course crucial to ensure participants are not exposed to extreme heat so temperatures up to 25 degrees are preferred. What would be interesting is how effective this method is during colder days, and what would be an acceptable minimum temperature for thermal walks during winter. Our current students are testing thermal walks for heat in Hengelo, and we hope to test winter conditions as well.