Why urban thermal comfort tools like ENVI-met and PET are critical for resilient city design

Rising heat across continents

Across Europe, a persistent heat dome has brought record-breaking temperatures from Portugal to the Balkans. Portugal registered its hottest June day at 46.6°C, while Spain, France, and Italy faced similar extremes. Cities responded with emergency measures: school closures, restrictions on outdoor work, and wildfire alerts. Even typically cooler regions such as the UK exceeded 33°C, with hundreds of suspected heat-related deaths.  In North America, New York, Toronto, and Washington, D.C. experienced highs of nearly 37°C, resulting in power outages and public transit disruptions. Meanwhile, northern India and Pakistan faced hazardous conditions as early as April, with temperatures reaching nearly 48°C.  These trends confirm what climate models have long predicted: heatwaves are becoming more frequent, more intense, and arriving earlier each year. Urban planners and designers must therefore integrate thermal comfort assessment into every stage of design to improve liveability and resilience.

ENVI-met: modelling the urban microclimate

ENVI-met is a 3D microclimate simulation software that models the interaction between air, surfaces, vegetation, and buildings. The tool supports data-driven design and helps quantify the impact of planning choices on thermal comfort at street level.

ENVI-met allows professionals to:

• Simulate airflow and heat exchange across densely populated neighborhoods.
• Model heat absorption and radiation from urban materials.
• Visualize the cooling effect of trees, green roofs, and shading structures.
• Quantify thermal comfort indices, such as PET (Physiological Equivalent Temperature) and UTCI (Universal Thermal Climate Index).

These capabilities make ENVI-met a practical choice for municipalities, engineering consultancies, and urban developers seeking to assess the thermal performance of open spaces before construction.

Understanding PET: human-centred heat measurement

To understand how people actually experience heat in cities, air temperature alone is not enough. Physiological Equivalent Temperature (PET) provides a human-centred metric that translates complex meteorological data into a single value in °C.

PET integrates:

• Solar and long-wave radiation
• Air temperature and humidity
• Wind speed
• Human factors such as activity level and clothing

This combination provides a more accurate reflection of perceived thermal comfort, enabling planners to design spaces that effectively mitigate heat stress. For instance, a PET analysis of Hyde Park, London, at 2 PM during the summer reveals how tree canopy density and material reflectivity influence visitor comfort levels (Figure 1).

Figure 1. Physiological Equivalent Temperature (PET) analysis of Hyde Park, London, at 2:00 PM during summer.

Applying ENVI-met and PET in urban design

Analyzing PET through ENVI-met enables professionals to:

• Identify heat-stress hotspots within new or existing developments.
• Test landscape and material alternatives before implementation.
• Demonstrate compliance with emerging thermal comfort regulations and green-building standards.
• Design more inclusive public spaces that ensure comfort for all users throughout the day.

In Madrid’s “Los Berrocales” development area, for example, 3D PET analysis with ENVI-met revealed how planting configuration and surface albedo directly influence pedestrian comfort (Figure 2). Such modelling guides design interventions that measurably reduce local air and surface temperatures.