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, the entire site falls within a fairly tight UTCI band of roughly 28.4°C to 31.1°C. The colour gradient, therefore does not depict a full cold-to-hot scale; instead, it ranks locations relative to one another, with deeper violets marking the coolest pockets (≈ 28 – 29°C) and pale yellows highlighting the warmest spots (≈ 31°C). The histogram quantifies this distribution, showing that most of the public realm clusters around 30.8 – 31°C, while only a small fraction drops below 29°C.

The map reveals meaningful variations: violet zones indicate cooler, potentially shaded areas that could be ideal for seating, walking paths, or gathering spaces. In contrast, yellow zones highlight sun-exposed facades and ground surfaces where additional shading elements, high-albedo materials or improved airflow could enhance comfort.

Thermal Comfort Statistics

The result of the simulation visualises how often each point on the site experiences heat-stress conditions during summer afternoons. In the legend this spans roughly 47% to 60% of the time. Pale oranges (≈ 47 – 52%) mark locations that encounter heat stress on roughly one out of two summer afternoons, whereas the deep reds (≈ 58 – 60%) highlight zones that are hot almost three days out of five.

The bar chart quantifies the map: the tallest bars sit in the 56 – 60% bins, confirming that a large share of pedestrian surfaces is heat-stressed on more than half of summer afternoons. Only a few bars appear in the lower-percentage ranges, indicating that relatively few areas experience heat stress infrequently during peak afternoon hours.

The darkest patches concentrate in wide, sun-exposed plazas and along unobstructed street canyons, signalling areas most in need of shade, high-albedo materials, or other mitigation methods such as evaporative cooling. Slightly lighter zones can be seen behind taller buildings, showing where shade and limited sky exposure help reduce heat levels.

The overall result shows that heat stress is widespread rather than occasional: on most summer afternoons, much of the site crosses the heat-stress threshold. This baseline makes a strong case for design measures—such as adding shade structures, re-orienting buildings to catch cooling breezes, or planting more vegetation—to lower the frequency of those deep-red hotspots and create cooler, more livable outdoor areas.