URBAN FORM-BASED CODES

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Context

The escalating issue of heatwaves in Indian cities, particularly focusing on the challenges posed by rising temperatures and the two-fold threat faced by both large and small cities.

Details

• Rising episodes and increasing intensity of heatwaves pose a significant problem in Indian cities.
• The issue affects both big and small cities, necessitating different approaches for adaptation.
• Big cities struggle with the "heat island" effect and require retrofitting, while small cities need heat-resilient master plans.

Challenges and Solutions for Big Cities

• Big cities face challenges in adapting to changing climates and improving liveability.
• Retrofits to combat the "heat island" effect are essential.
• Parameters like urban morphology, aspect ratio, and blue/green infrastructure influence heat resilience.
• Open highrise, open midrise, and compact mid rise urban morphologies show lower land surface temperatures (LST).
• Low Rise buildings with sparse vegetation contribute to higher LST.
• Recommendations include using better roofing materials, reflective paints, and green roofs.

Strategies for Small Cities on the Brink of Growth

• Small cities experiencing explosive growth need "heat-proof" development.
• Heat-resilient master plans and by-laws are crucial.
• Urban form parameters impact heat resilience and liveability.
• Parameters such as aspect ratio, sky view factor, and blue/green infrastructure influence heat resilience.
• Higher aspect ratios lead to lower LST by reducing direct sun exposure.
• Sky view factor between 0.2 and 0.9 raises LST by 10°C.
• Effective vegetation cover (EVC) reduces LST; trees with canopy have the greatest impact.
• Cities must reconsider green area planning in master plans.

Key Urban Form Parameters and Their Impact

1.Urban Morphology:

• Different urban morphologies impact heat resilience.
• Open highrise, open midrise, and compact midrise morphologies have lower LST.
• Low Rise neighborhoods with sparse vegetation experience higher LST.

2.Aspect Ratio:

• Aspect ratio (building height to street width) influences heat trapping.
• Higher aspect ratios lead to lower LST by reducing direct sun exposure.
• Narrower streets decrease heat gain by shading surfaces.

3.Sky View Factor (SVF):

• SVF influences heat trapping and dissipation.
• Higher SVF values lead to increased LST, especially in highways and intersections.

4.Blue/Green Infrastructure (B/GI):

• Green spaces regulate temperature, air quality, and humidity.
• Effective vegetation cover (EVC) reduces LST; trees are most impactful.
• Trees with thick foliage result in significantly cooler temperatures.

5.Floor Space Index (FSI):

• High FSI corresponds to lower LST.
• Pune's FSI range (100-300) led to LST variation.

6.Street Orientation:

• Street orientation affects heat gain due to sun exposure and wind.
• North-south oriented streets have higher LST due to sun exposure.

Neighbourhood Planning and Contextual Cooling Solutions

• Urban form-based codes offer solutions tailored to cities and neighborhoods.
• Different zones could have cooling features, e.g., shaded walkways in markets, cool roofs in temple precincts, high EVC in business districts.
• Building by-laws and master plans need amendments to address specific drivers of heat gain.
• A 1°C temperature reduction can lead to a 2% decrease in the city's power bill.

https://www.downtoearth.org.in/news/governance/road-to-cool-cities-codes-based-on-unique-urban-form-can-be-helpful-91367