Evaluating Outdoor Thermal Comfort in Two Neighborhoods of Sulaimani City

A research study conducted by Chro Hama Radha and Mohammed Jalal Mohammed from the Department of City Planning at Sulaimani Polytechnic University evaluated outdoor thermal comfort in two residential neighborhoods of Sulaimani City: Nawroz and Nali.

The study examined how urban design elements, including street geometry, building arrangement, vegetation, pavement materials, shading, and exposure to the sky, influence outdoor temperatures during extreme summer conditions.

Using ENVI-met environmental simulation software, the researchers modeled both neighborhoods at 12:00 p.m. on 27 July 2021, which was identified as the hottest day of that year.

Why This Research Matters

Outdoor thermal comfort influences how people use streets, pedestrian routes, public spaces, and residential environments. In hot and dry cities such as Sulaimani, poorly designed neighborhoods may expose residents to excessive heat, reduce outdoor activity, and increase dependence on indoor cooling.

Urban expansion can also reduce vegetation and replace natural surfaces with concrete and asphalt. These surfaces absorb and retain heat, contributing to higher air and surface temperatures.

The research highlights the importance of including climatic and environmental considerations in neighborhood planning. Climate-responsive design can create healthier outdoor spaces, support urban activity, and potentially reduce the energy required to cool buildings.

Research Objective

The main objective was to compare the thermal performance of Nawroz and Nali and determine how differences in their urban design affected outdoor conditions.

The researchers examined:

• Street canyon depth and geometry
• Building height and spacing
• Vegetation coverage
• Pavement materials
• Shading patterns
• Sky view factor
• Air temperature
• Mean radiant temperature

Methodology

The two neighborhoods were recreated in ENVI-met using information about their buildings, streets, vegetation, open spaces, and construction materials.

Meteorological information was obtained from the relevant meteorological authority in Sulaimani. The simulations were conducted at midday on the hottest recorded day of 2021 to represent severe summer conditions.

Comparison of the Two Neighborhoods

Model Area Information

Key Results

The simulations showed that neither neighborhood provided fully comfortable outdoor conditions during the selected extreme summer period. However, Nawroz performed better than Nali.

Nali was approximately 0.83°C hotter on average than Nawroz. Although the numerical difference may appear relatively small, it reflected clear differences in neighborhood design and exposure to solar radiation.

The average temperature in both neighborhoods was also above the highest summer temperature range referenced from ASHRAE Standard 55:2010 in the study.

Why Nawroz Performed Better

Several design characteristics helped Nawroz achieve comparatively lower air and radiant temperatures:

• Deeper street canyons created more shade around buildings and pedestrian areas.
• Narrower spaces between buildings reduced direct solar exposure.
• Higher vegetation coverage supported local cooling and protected surfaces from direct sunlight.
• A lower sky view factor reduced the amount of visible sky and incoming solar radiation.
• High-albedo pavement materials absorbed heat more slowly and reflected more solar radiation.
• Compact building arrangements produced stronger and more continuous shading patterns.

By comparison, Nali had wider open spaces, shallower street canyons, less vegetation, and more low-albedo asphalt. These conditions increased the exposure of streets and surrounding surfaces to sunlight.

Mean Radiant Temperature

Mean radiant temperature represents the combined radiant heat received from the sun and surrounding surfaces.

The study found that shaded and planted areas near buildings had lower mean radiant temperatures in both neighborhoods. However, the highest values were observed in Nali.

This was associated with:

• Limited vegetation and fewer shaded areas
• Greater distance between buildings
• A higher sky view factor
• Wider streets
• More direct and reflected solar radiation
• Heat emitted from sun-exposed buildings and pavement
• Greater use of low-albedo surface materials

Main Research Findings

• Outdoor temperatures were lower near shaded buildings and planted areas.
• Large exposed spaces without vegetation absorbed and stored more heat.
• Street canyon geometry directly influenced shade and thermal performance.
• Aspect ratio and sky view factor affected the amount of solar radiation reaching streets and pedestrians.
• Vegetation coverage contributed to cooler microclimatic conditions.
• Narrow streets generally provided better shade than wide streets.
• Pavement and construction materials influenced heat absorption, storage, and transfer.
• Street orientation and canyon design could support airflow and improve outdoor cooling.
• Urban design strategies should be considered together rather than as isolated elements.

Implications for Urban Planning

Conclusion

The study concluded that neither Nawroz nor Nali achieved satisfactory outdoor thermal comfort under the simulated extreme summer conditions. Nevertheless, Nawroz demonstrated better thermal performance because of its deeper street canyons, more compact building arrangement, higher vegetation coverage, stronger shading patterns, and use of higher-albedo pavement materials.

The findings show that outdoor thermal comfort is strongly connected to the physical design of neighborhoods. Integrating vegetation, appropriate street proportions, suitable building spacing, reflective materials, and effective shading into urban planning can reduce heat exposure and create more comfortable outdoor environments.

The research emphasizes that climate-responsive planning should become an essential part of future urban development in Sulaimani City.

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