Key Performance Indicators (KPIs) are defined as spatial metrics used to evaluate and compare environmental conditions in urban areas, particularly outdoor thermal environments. Each KPI expresses a quantitative assessment of a specific environmental category, based on extracted values computed over a given spatial domain (e.g., a neighborhood, park, or plaza, depending on the site area).

All indicators are calculated by analyzing the percentage of surface area (in m²) that falls within specific metric thresholds—defined based on literature, referenced case studies, guidelines, and expert knowledge—which reflect comfort and discomfort conditions. Therefore, these percentages represent how much of the total urban area is exposed to beneficial (e.g., comfort zones) or harmful (e.g., heat-stress zones) environmental conditions. All KPIs have been normalized by converting diverse raw data into a standardized scale—typically 0–100%—to allow for fair comparison and a clear understanding of performance relative to a maximum possible value or ideal state.

This approach allows planners and designers to map, quantify, and compare the performance of different urban configurations or interventions in promoting thermal well-being.

Wind Speed

Ventilation Assessment

These KPIs are designed to assess the potential for natural ventilation and wind-related risks in urban environments. They provide quantitative measures of how different urban layouts influence air movement, which is critical for pedestrian comfort, air quality, and safety.

• Ventilation Assessment
  • Goal: To evaluate natural ventilation potential and identify areas of air stagnation.
  • Why It’s Performed: To ensure that the majority of an urban space has sufficient wind speeds (typically 0.3 m/s or higher) to prevent the buildup of air pollution and heat.
  • User Benefit: Users benefit from cleaner air and a more refreshing environment, especially in densely built areas, as this KPI helps avoid stagnant, stuffy zones.
• Comfort Wind Areas
  • Goal: To quantify the percentage of an area with optimal wind speeds for general pedestrian activities.
  • Why It’s Performed: To measure the portion of a space that falls within a comfortable wind speed range (e.g., 1.3 m/s to 5 m/s), which is ideal for a variety of activities without being disruptive.
  • User Benefit: This ensures that a large portion of the urban space is pleasant for users, providing a comfortable experience for activities like walking, standing, or simply being outdoors.
• Safe Wind Areas
  • Goal: To avoid safety risks by identifying areas where wind speeds exceed a dangerous threshold.
  • Why It’s Performed: To quantify the percentage of a space that remains below a high-risk wind speed (e.g., 10 m/s), thereby minimizing the risk of pedestrian falls or other wind-related accidents.
  • User Benefit: This KPI directly contributes to the physical safety of users by ensuring that urban design does not create hazardous wind zones.

You can find references here (Link 1), here (Link 2), here (Link 3), here (Link 4).

Wind Comfort

Pedestrian Wind Comfort

These KPIs quantify how suitable urban areas are for year-round pedestrian activity. They describe the percentage of an area that remains within acceptable thresholds for pedestrian comfort throughout the year, using criteria that combine both occurrence frequency and exceedance probability. The goal is to provide a long-term assessment of comfort and safety based on established standards.

• Extended Use Area
  • Goal: To measure the percentage of an area suitable for prolonged outdoor use.
  • Why It’s Performed: To determine the proportion of urban space where long-term sitting and leisure activities are viable based on year-round wind conditions. The assessment uses specific wind speed thresholds (e.g., below 1.5-2.0 m/s) with a very low exceedance probability (e.g., 5-10%).
  • User Benefit: Provides assurance that spaces intended for extended, stationary use will be comfortable and enjoyable for a significant portion of the year.
• Transient Use Area
  • Goal: To measure the percentage of an area within an acceptable wind comfort range for general activities.
  • Why It’s Performed: To assess the overall long-term suitability of a space for a wide range of pedestrian movements and activities. This applies wind speed thresholds such as 3.0-5.0 m/s with a moderately low exceedance probability (e.g., 10-15%).
  • User Benefit: Ensures that major pedestrian thoroughfares and public spaces remain comfortable and functional throughout the year.
• Pedestrian Safety Area
  • Goal: To measure the percentage of an area not exposed to high-risk wind speeds.
  • Why It’s Performed: To ensure that the design provides a safe environment free from dangerously high wind speeds throughout the year. This uses high wind speed thresholds, often above 15 m/s, with an extremely low exceedance probability (e.g., < 0.1%).
  • User Benefit: This is a critical safety measure that protects users from the risk of injury due to dangerously strong winds.

You can find references here.

Thermal Comfort Index

Thermal Sensation

These KPIs evaluate the thermal quality and homogeneity of a space using the Universal Thermal Climate Index (UTCI), a key metric for assessing human thermal sensation in outdoor environments.

• Comfort Relief Score
  • Goal: To represent the percentage of an area that provides positive thermal comfort relief.
  • Why It’s Performed: To measure how much of the space falls within the optimal thermal comfort range of 18∘C ≤ UTCI ≤ 26∘C.
  • User Benefit: Users can find areas that are thermally pleasant and comfortable, which is especially important on hot or cold days.
• Thermal Stability Score
  • Goal: To minimize transitional thermal areas, indicating stable thermal conditions.
  • Why It’s Performed: To avoid zones where the UTCI falls between 9∘C ≤ UTCI < 18∘C or 26∘C < UTCI ≤ 32∘C, which represent fluctuating and unstable thermal environments.
  • User Benefit: Ensures a more predictable and consistent thermal experience for users, preventing abrupt changes in temperature perception.
• Thermal Safety Score
  • Goal: To identify the percentage of an area that is free from extreme thermal stress.
  • Why It’s Performed: To ensure that the space avoids dangerous temperature zones where UTCI < 9∘C or UTCI > 32∘C.
  • User Benefit: This protects users from potentially dangerous cold or heat stress, contributing directly to public health and safety.

You can find references here (Link 1), here (Link 2), here (Link 3).

Thermal Comfort Statistics

Thermal Comfort Indexes

These KPIs provide a statistical overview of an urban environment’s thermal conditions, assessing consistency and protection from discomfort.

• High Comfort Exposure
  • Goal: To measure the percentage of an area that achieves a high-comfort-time target of 70% or more.
  • Why It’s Performed: To ensure that the space is designed to provide comfortable thermal conditions for a significant portion of the time.
  • User Benefit: Users can rely on the space to be thermally comfortable most of the time, making it a reliable and pleasant environment for regular use.
• Comfort Consistency Score
  • Goal: To describe the percentage of an area with low deviation from thermal comfort levels.
  • Why It’s Performed: To ensure that thermal variability is below a 30% standard deviation, indicating a stable and predictable thermal environment.
  • User Benefit: This prevents users from experiencing a “patchwork” of hot and cold spots, providing a uniform and predictable thermal experience.
• Low Comfort Protection
  • Goal: To measure the percentage of an area that avoids low comfort conditions.
  • Why It’s Performed: To quantify the percentage of an area that does not experience comfort conditions below a 25% threshold, thereby protecting users from consistently uncomfortable conditions.
  • User Benefit: Ensures a baseline level of pleasantness throughout the urban space, avoiding large, consistently uncomfortable zones.

You can find references here.

Cold Stress Indexes

These KPIs specifically quantify an urban environment’s exposure to cold stress conditions, providing critical insight for designing resilient and safe spaces in colder climates.

• Low Cold Exposure
  • Goal: To describe the percentage of an area with a mean exposure to cold stress below a 50% threshold.
  • Why It’s Performed: To ensure that the overall exposure to cold stress in a given area is minimal.
  • User Benefit: This helps minimize the time users spend in unpleasantly cold conditions, making outdoor spaces more usable in colder weather.
• Cold Resilience Score
  • Goal: To measure the percentage of an area with mean deviation from cold stress levels below a 75% threshold.
  • Why It’s Performed: To ensure that cold stress levels are not widely fluctuating, indicating a more stable and resilient thermal environment.
  • User Benefit: Users can expect a consistent thermal experience, reducing the risk of sudden drops in temperature that could lead to discomfort or health risks.
• Extreme Cold Protection
  • Goal: To describe the percentage of an area that avoids severe cold stress exposure above a 50% threshold.
  • Why It’s Performed: To identify and reduce the presence of dangerously cold zones for user safety.
  • User Benefit: This KPI is vital for public safety, as it ensures that extreme cold conditions are mitigated, protecting users from health risks like hypothermia.

You can find references here.

Heat Stress Indexes

These KPIs quantify an urban environment’s exposure to heat stress conditions, providing essential insight for creating comfortable and safe spaces in warmer climates.

• Low Heat Exposure
  • Goal: To describe the percentage of an area where the mean exposure to heat stress is below a 60% threshold.
  • Why It’s Performed: To ensure that the overall exposure to heat stress in an area is kept to a minimum.
  • User Benefit: Users are protected from consistently high temperatures, making outdoor spaces more functional and pleasant during hot weather.
• Heat Resilience Score
  • Goal: To measure the percentage of an area with mean deviation from heat stress levels below a 75% threshold.
  • Why It’s Performed: To ensure that heat stress levels are stable and do not show large fluctuations, indicating a resilient design.
  • User Benefit: A stable thermal environment prevents sudden spikes in temperature, which can be particularly dangerous and uncomfortable for users.
• Extreme Heat Protection
  • Goal: To describe the percentage of an area that avoids severe heat stress exposure above a 50% threshold.
  • Why It’s Performed: To identify and reduce the presence of dangerously hot zones for user safety and well-being.
  • User Benefit: This is a critical safety measure that protects users from the health risks associated with extreme heat, such as heatstroke.

You can find references here.