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.
  • Measures air movement adequacy for pollutant dispersion and thermal regulation
  • Prevents the creation of stagnant microclimates that compromise air quality and health
• 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.
  • Quantifies the spatial extent of optimal wind conditions for pedestrian activities
  • Determines the usable area percentage where wind enhances rather than hinders outdoor experience
• 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.
  • Identifies wind speed thresholds that separate comfortable from hazardous conditions
  • Prevents the creation of wind tunnels that could cause pedestrian accidents or injuries

You can find references

,

,

,

.

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.
  • Defines zones suitable for stationary activities requiring minimal wind disturbance
  • Determines whether outdoor spaces can support sedentary social and commercial activities
• Transient Use Area
  • Goal: To measure the percentage of an area within acceptable comfort range for short-duration activities.
  • Why It’s Performed: To assess the overall suitability of urban spaces for general pedestrian movement and brief outdoor activities. The assessment applies comfort bin limits that vary by standard, ensuring compatibility with internationally recognized wind comfort criteria.
  • User Benefit: Ensures that pedestrian pathways, plazas, and public spaces remain comfortable for everyday activities like walking, brief stops, and general circulation throughout the year.
  • Measures the baseline wind comfort necessary for general pedestrian circulation
  • Ensures that movement through urban spaces remains pleasant rather than physically challenging
• Pedestrian Safety Area
  • Goal: To measure the percentage of an area not exposed to high-risk wind conditions.
  • Why It’s Performed: To ensure the urban environment is free from dangerously high wind speeds that could pose safety risks to pedestrians. This assessment identifies and excludes unsafe wind condition bins (typically the highest wind speed categories in each standard, such as the last 1-3 bins depending on the criteria used).
  • User Benefit: This critical safety measure protects users from potential injury due to strong winds that could cause loss of balance, difficulty walking, or create hazardous conditions for vulnerable populations including elderly individuals and children.
  • Quantifies protection from wind speeds that could cause loss of balance or control
  • Critical for ensuring vulnerable populations can safely navigate outdoor urban environments

You can find references here.

Thermal Comfort Index

Thermal Quality Assessment

These KPIs evaluate the thermal quality and spatial consistency of outdoor environments using temperature-based metrics that assess uniformity, optimization, and livability conditions.

• Spatial Variance Reduction Index
  • Goal: To assess temperature uniformity with dynamic baseline variance analysis.
  • Why It’s Performed: To measure how effectively the design reduces temperature variations across the space, ensuring optimal thermal consistency.
  • User Benefit: Users experience more predictable and comfortable thermal conditions without dramatic temperature fluctuations between different areas of the space.
  • Represents acceptable temperature uniformity (≤3°C standard deviation)
  • Determines whether users can move freely through the space without encountering thermal barriers
• Livability Gradient Index
  • Goal: To measure the percentage of area within optimal temperature ranges with graduated scoring.
  • Why It’s Performed: To assess coverage within the optimal 18°C-26°C temperature range while providing graduated scoring for near-optimal conditions.
  • User Benefit: - Ensures that most of the space provides thermally comfortable conditions suitable for extended outdoor activities and general use.
  • Indicates good coverage of optimal temperature range (18-26°C)
  • Directly correlates with how long people can comfortably remain in outdoor spaces
• Temperature Uniformity Index
  • Goal: To describe temperature uniformity using standard deviation approach for enhanced sensitivity.
  • Why It’s Performed: To quantify how well the design distributes heat and reduces temperature variations across the area.
  • User Benefit: Prevents the formation of uncomfortable hot spots, creating a more evenly distributed and pleasant thermal environment for all users.
  • Shows acceptable temperature uniformity using standard deviation approach
  • Eliminates thermal inequity that could exclude certain user groups from portions of the space

You can find references

,

.

Thermal Comfort Statistics

Thermal Comfort Performance

These KPIs provide statistical analysis of thermal comfort conditions, focusing on consistency, opportunity, and average comfort performance across time and space.

• Range-Based Comfort Score
  • Goal: To assess comfort performance using range penalty analysis.
  • Why It’s Performed: To evaluate overall comfort performance while penalizing excessive variability for reliable thermal conditions.
  • User Benefit: Ensures that comfortable conditions are not only achieved but maintained consistently, providing users with predictable thermal comfort.
  • Indicates comfort levels consistency
  • Prevents thermal discomfort that could limit space accessibility and usage duration
• Average Condition Comfort
  • Goal: To describe comfort consistency with adaptive tolerance based on performance level.
  • Why It’s Performed: To assess how consistently comfortable conditions are maintained across different areas and times for stable thermal environments.
  • User Benefit: Provides assurance that thermal comfort is reliable and consistent, allowing users to plan activities without concern for thermal variability.
  • Shows sustained thermal comfort performance
  • Measures the difference between theoretical comfort and lived thermal experience
• Comfort Opportunity Index
  • Goal: To measure fine-sensitivity occupancy-weighted comfort.
  • Why It’s Performed: To evaluate comfort opportunities for users while rewarding high-performing designs that exceed standard thresholds.
  • User Benefit: Identifies spaces that not only meet comfort standards but provide exceptional thermal conditions, enhancing overall user satisfaction and space utilization.
  • Represents high-opportunity comfort scenarios
  • Maximizes the potential for extended outdoor occupancy and social interaction

You can find references here (Link 1), here (Link 2), here (Link 3), here (Link 4), here (Link 5).

Heat Stress Management

These KPIs specifically address heat stress conditions, evaluating protection strategies and thermal resilience in warm climate conditions.

• Heat Range Optimization
  • Goal: To assess heat stress reduction with enhanced sensitivity to temperature variations.
  • Why It’s Performed: To evaluate how effectively the design minimizes heat stress exposure while maintaining consistency across different areas.
  • User Benefit: Protects users from excessive heat exposure, making outdoor spaces more usable and safer during warm weather conditions.
  • Indicates heat stress consistency
  • Prevents heat-related health risks that could render outdoor spaces unusable during peak temperatures
• Average Heat Condition
  • Goal: To describe heat condition consistency using adaptive assessment methods.
  • Why It’s Performed: To ensure that heat stress levels remain manageable and consistent throughout the space for safe thermal conditions.
  • User Benefit: Provides reliable protection from heat stress, ensuring that users can safely use outdoor spaces even during warmer periods.
  • Shows sustained heat stress mitigation
  • Critical for maintaining outdoor space functionality during increasingly frequent heat events
• Heat Vulnerability Reduction
  • Goal: To assess heat vulnerability reduction across all percentage ranges of heat exposure.
  • Why It’s Performed: To quantify how well the design protects vulnerable populations from heat stress for inclusive thermal safety.
  • User Benefit: Ensures that outdoor spaces are accessible and safe for all users, including children, elderly, and those with health sensitivities to heat.
  • Indicates effective heat vulnerability mitigation
  • Focus on protecting vulnerable populations

You can find references here (Link 1), here (Link 2), here (Link 3), here (Link 4), here (Link 5).

Cold Stress Protection

These KPIs evaluate cold stress conditions and protection strategies, ensuring thermal safety and comfort in cooler climate conditions.

• Cold Range Optimization
  • Goal: To assess cold stress reduction using high-sensitivity analysis.
  • Why It’s Performed: To evaluate how effectively the design minimizes cold stress while maintaining thermal consistency for cold weather resilience.
  • User Benefit: Enables year-round use of outdoor spaces by providing protection from cold stress and maintaining comfortable conditions during cooler periods.
  • Indicates cold stress consistency
  • Prevents outdoor spaces from becoming seasonally inaccessible due to thermal hostility
• Average Cold Condition
  • Goal: To describe cold condition consistency with improved adaptive requirements.
  • Why It’s Performed: To ensure that cold stress levels are minimized and remain consistent across different areas for reliable cold weather protection.
  • User Benefit: Provides predictable protection from cold stress, allowing users to comfortably utilize outdoor spaces throughout different seasons.
  • Shows sustained cold stress mitigation
  • Prevents hypothermic conditions that could pose serious health risks to users
• Cold Protection Index
  • Goal: To assess cold protection using balanced sensitivity analysis.
  • Why It’s Performed: To evaluate comprehensive cold weather protection while rewarding designs that provide exceptional cold stress mitigation.
  • User Benefit: Ensures robust protection from cold-related discomfort and health risks, making outdoor spaces welcoming and safe during cold weather conditions.
  • Represents excellent cold protection performance
  • Higher target reflects severity of cold exposure impacts

You can find references here (Link 1), here (Link 2), here (Link 3), here (Link 4), here (Link 5).