Project Details

Mitigating the Urban Heat Island Effect

 

 

Material Selection and Assessment

 

In selecting solutions to reduce the urban heat island effect, HPBS developed a material assessment framework based on Solar Reflectance Index (SRI) and Solar Reflectance (SR, albedo) values.

 

These indicators became the foundation for material selection:

• minimum reference SRI/SR values were established for roofs, pavements, and architectural elements (aligned with LEED v4 principles);
• recommended value ranges were defined for different surface types, including concrete, natural stone, permeable pavements, wood-plastic composites, rubber surfaces, and others.

 

Analysis of the Client’s Material List

 

Each material provided by the client was analysed in detail:

• thermal performance characteristics were assessed, including SRI/SR values and weathered performance after climatic exposure;
• advantages and limitations were identified in relation to Tashkent’s climate;
• critically unsuitable materials - those with low reflectance and high heat capacity that intensify overheating - were excluded.

 

Prioritisation of Surface Types

 

The recommendations highlighted several priority solutions:

• light-coloured concrete pavements and tiles as a primary tool for reducing surface overheating;
• locally sourced light-coloured natural stone (limestone, travertine, dolomite, light granite);
• permeable pavements (eco-pavers, paving with wide joints and light infill) as «2-in-1» solutions combining cooling and water permeability;
• green and cool roofs with high SRI values; shading structures - pergolas and canopies, including those integrated with solar panels - as a complementary measure to surface materials.

 

 

 

 

 

Heat Island Reduction Modelling: New Tashkent Block

 

HPBS performed a comparative analysis based on the master plan of one of the New Tashkent blocks, assessing several scenarios:
•     baseline conditions dominated by dark asphalt surfaces and roofs;
•    scenarios with partial replacement of surfaces with light-coloured materials;
•    combined scenarios integrating high-reflectance roofs, light external surfaces, and greenery (trees and lawns).

 

The modelling demonstrated that:
•    heat island reduction targets (analogous to LEED requirements) can be achieved without total replacement of all surfaces, through a combination of reflective roofs and greenery;
•    the most effective approach is integrated: partial replacement with light or permeable surfaces, reflective or green roofs, and additional shading from trees and canopies;
•    this strategy reduces thermal stress while optimising project costs. 

 

Key Conclusion on Urban Heat Island Mitigation

A city does not need to «paint everything white».
A far more effective approach is to define reasonable target SRI/SR values, identify critical overheating zones, and selectively replace materials, complementing them with greenery and shading solutions.
This approach has been embedded in the urban design code as a system of requirements and checklists. 

 

 

Biodrainage Systems and Green Infrastructure in an Arid Climate

 

International stormwater management practices were adapted to the climatic conditions of Central Asia and Tashkent.
HPBS considers green infrastructure - combining green spaces with engineering solutions such as permeable pavements, rain gardens, bioswales, and related systems - as a core element of a sustainable master plan, rather than residual landscaping. 

 

 

 

 

Analysis of Biodrainage Solutions

The report provides a systematic review of key biodrainage systems, including:

bioswales and biofiltration slopes;
rain gardens, bioplato systems, bioponds, and constructed wetlands;
phytofilters;
permeable pavements and underground systems for runoff retention and filtration;
building-integrated greenery, including green roofs, as part of the overall system.

 

 

 

 

Adaptation to Tashkent’s Conditions

 

Considering the arid climate and high level of urbanisation, several key conclusions were reached:

• not all «classic» green solutions widely used in Europe and North America (such as certain types of rain gardens and wetlands) are equally effective in Tashkent;
• green roofs contribute to microclimate improvement and runoff retention, but their role as primary biodrainage systems is limited - and this is transparently acknowledged;
• the most suitable solutions for arid, highly urbanised areas like Tashkent include:

o    filtration (biodrainage) slopes;
o    biodrainage channels;
o    permeable pavements and subsurface filtration layers;
o    phytofilters with carefully selected vegetation.
 

 

 

 

HPBS also defined criteria for selecting appropriate biodrainage systems:
•    engineering and geological conditions;
•    groundwater levels;
•    type and concentration of pollutants;
•    required treatment performance and the feasibility of infiltration or runoff detention.
 

 

 

 

 

 

Design Checklists for Practitioners

A key project outcome was the development of practical design checklists, covering:
•    layout principles and integration into street and road networks;
•    plant selection requirements for arid climates;
•    operation and maintenance considerations;
•    recommendations for coordination with surface materials and landscaping.