With the latest update to the Infrared Web App, users can now assess outdoor thermal comfort with two new tools: Thermal Comfort Index and Thermal Comfort Statistics. These features help designers, planners, and researchers better understand microclimatic heat conditions in urban spaces—and ultimately support more livable cities.

In this tutorial, we will walk through how to use both tools, explore what the results mean.

Why Thermal Comfort Matters

Thermal comfort analysis helps evaluate how hot or cool outdoor spaces feel to people, based on factors like air temperature, radiation, humidity, and wind. These analyses support critical design decisions, especially in dense cities where heat stress can severely impact walkability, health, and quality of life. Use cases include:

• Designing plazas, courtyards, or parks that remain usable in summer
• Identifying heat-stressed zones during specific time periods
• Testing how urban form and shading influence outdoor temperatures
• Comparing seasonal or hourly comfort levels across multiple design iterations

New to infrared.city?

If this is your first time using the infrared.city, we recommend reading our running your first simulation guide where we explain how to set up a project, import your geometry, and run your first simulation.

Step 1: Add Your Analysis

Start by opening your project in infrared.city. You can analyse the existing city environment or import your own 3D design geometry to test how your proposal performs under different thermal comfort conditions.

Then click “Add Simulation” and choose either:

Thermal Comfort Index

The simulation helps you assess how hot or thermally comfortable outdoor spaces feel at a specific moment, based on the Universal Thermal Climate Index (UTCI). The UTCI integrates multiple environmental factors—including air temperature, humidity, wind speed, and radiation—into a single value that reflects human thermal perception.

Goal: You can use this analysis to evaluate stress categories and optimize outdoor spaces like plazas, courtyards, streets, or schoolyards for thermal comfort during critical periods of use.

Especially useful for testing design options where comfort during specific times of day matters—such as outdoor dining zones, waiting areas, school recess spaces, or evening promenades.

Thermal Comfort Statistics

The simulation provides a deeper understanding of how frequently specific thermal conditions occur in outdoor spaces over time. Rather than analyzing a single point in time, this tool evaluates patterns across an entire season or the full year, helping you answer critical questions like:

• How often is this space comfortable to use?
• Is heat stress a recurring problem in summer?
• Do certain areas consistently provide thermal comfort throughout the year?

By calculating the percentage of time a location experiences various UTCI-based thermal comfort or stress levels (e.g. Cold Stress, Heat Stress, Thermal Comfort), the analysis highlights microclimatic risk zones and supports long-term design strategies for public health, safety, and livability.

Goal: The aim is to design year-round usable outdoor environments. Use this simulation to guide decisions on vegetation, shading, and building orientation, ensuring that your interventions reduce heat risks, extend outdoor usability, and support healthier public spaces in both hot and cold seasons.

Especially valuable for long-term urban planning, climate adaptation strategies, and outdoor programs that require reliable comfort across time.

Step 2: Set Time and Season for Your Simulation

Thermal Comfort Index

Use case: This analysis is ideal for point-in-time assessments, allowing you to test thermal comfort during specific months and hour blocks such as morning, noon, afternoon and evening. For example, you might want to understand heat stress on a summer afternoon, or explore comfort levels on a winter morning in a shaded public space.

Thermal Comfort Statistics

Use case: This simulation is ideal for climate-resilient design and seasonal planning. You can use it to evaluate how well a public space performs not just during one hot afternoon, but throughout an entire summer or year. It helps designers and urban planners identify chronically exposed or consistently comfortable zones—whether for schoolyards, parks, plazas, streetscapes, or courtyards.

You can run the simulation using Full Year settings to get a holistic view of the thermal behaviour across time. This is especially useful in early-stage planning, where you need to identify long-term performance trends and make strategic decisions based on usage frequency rather than momentary conditions.

Step 3: Review the Results

After adding your simulation and selecting the desired month and hour range, click Run All Simulations to start the analysis. Once completed, you can view the output by expanding the Results panel.

Thermal Comfort Index

As a result of the simulation, August afternoons (14:00–18:00) place the site within a UTCI band of roughly 28.4–31.1 °C. The histogram shows a clear concentration in the 29.2–29.6 °C bins, with a secondary spread through 29.9–30.5 °C, and only small tails below 28.8 °C or above 30.9 °C. In other words, most of the public realm clusters around warm-neutral conditions, with fewer pockets at the hotter extreme.

On the map, deep violets and purples (≈ 28.5–29.5°C) identify shaded corridors and building footprints that remain comparatively cooler, often aligning with tree-lined routes or narrow passages. These areas suggest natural microclimatic buffers where pedestrians could find relief from heat stress. In contrast, orange to yellow patches (≈ 30.5–31°C) highlight sun-exposed plazas and open street sections, particularly around south-facing facades and wider junctions, where heat accumulation is more pronounced.

Thermal Comfort Statistics

The result of the simulation visualises how often each point on the site experiences heat-stress conditions during summer afternoons (June–September, 14:00–18:00). The legend spans roughly 47% to 58% of the time, meaning nearly all public spaces face frequent exposure.

The histogram peaks around the 52–55% bins, showing that most of the site experiences heat stress on more than one in two afternoons. Only a small share of surfaces fall into the lower ranges below 50%, while fewer areas reach the upper extreme of 57–58%.

On the map, lighter oranges (≈ 48–51%) highlight semi-shaded pockets and narrow passages where nearby buildings or tree cover reduce direct solar load. By contrast, darker reds (≈ 55–58%) cluster in wide, sun-exposed plazas and open street canyons, marking the most critical hotspots.

These variations indicate that while heat stress is widespread, targeted shading strategies, reflective paving, or cooling interventions in the darkest red zones would substantially improve comfort, while lighter areas may already benefit from urban form and can be reinforced with vegetation continuity.

The overall outcome confirms that heat stress is not an isolated occurrence but a frequent condition, with much of the site exposed on more than half of summer afternoons. While some shaded pockets perform slightly better, the persistence of 52–55% heat-stress frequency across most surfaces highlights the urgency of mitigation. Introducing additional shading, reflective or cooler paving materials, and strategic vegetation would help reduce the intensity of the deep-red hotspots and shift everyday outdoor conditions toward greater comfort and livability.