Aschak Damani | GreenShield on September 2019 As our populations migrate from rural interiors to urban cities for better opportunities and life improvement, there is tremendous amount of up-scaling happening in our cities. There is more urbanization, more buildings – residences, offices, factories, malls, schools, colleges, hospitals, transport hubs – metros, bus, rail, airports, roads. All of these developments are significantly changing the landscape across the city. Open lands, trees, water bodies are being replaced with concrete, stone, glass, metal and bitumen – all of which increase the heat absorption and retention within the cities.
As urbanization increases, our populations in the city face several issues. A prominent one is the phenomenon of Urban Heat Island Effect (UHIE).
UHI is a city area where temperatures are higher vis-à-vis a less dense, more open rural area. During the day, the cities are warmer by around 5oC whereas at nights the difference is as high as to 12oC, in comparison to surrounding rural areas.
Prominent causes for UHI are:
- Increased urban densification: Use of impermeable, high emissivity surfaces such as concrete, asphalt that absorb & retain heat and radiation. Roofs of buildings, which form almost 60 – 80% of a city ground cover, are concrete or metal that high heat absorbing surfaces.
- Building height and gaps: Higher height, smaller gaps, narrower roads lead to higher heat and radiation entrapment and reducing wind tunnel effect.
- Reduced Green Cover:Declining Green Cover & lower water permeation reduces evapotranspiration effect which lower humidity levels and thus lowers the natural cooling effect
- Increased anthropogenic heat: Increase in vehicle pollution, air conditioning, fossil fuel burning, increased GHG emissions all lead to increased heat entrapment within the cities.
Effects of UHI are:
- Deterioration of living environment: Increased pollution & haze results in health risks – heat strokes, asthma and breathing issues, increased mortality rate, worsening quality of life.
- Increased energy consumption: Studies across Indian cities have shown that a 0.5oC increase in ambient temperature leads to 2% rise in energy consumption – fans, coolers, air conditioners, refrigerators.
- Increased ground level ozone.
- Reduced pedestrian and cycle riding activities – increase in vehicular traffic and thus pollution.
- Reduced water permeation: As permeable land is replaced with impermeable concrete and asphalt – ground water recharge reduces – leading to shortages in water over longer time.
- Deterioration of infrastructure: As ambient temperatures rise and with overall climate change, infrastructure deteriorates. Roads melt (Delhi, May 2015), Electronics overheat, power outage frequency increases, depleting water levels (Chennai, June 2019)
Changing weather pattern 2019:
Climate change is now an integral part of our lives. Periodicity of seasons have changed. In 2019, we witnessed one of the longest heat waves in recent history. High heat was observed for over 30 days across the country. Chennai witnessed acute water scarcity. We also observed one of the longest prolonged rain season in almost 2 decades – where there was excess rains and flooding across Maharashtra, Kerala & Karnataka and deficiency across East, North- East &North-West parts of India.
These changes put further pressure across our cities as increased impermeable surfaces and without proper drainage systems, water run-off and ground water seepage is a problem.
Techniques to reduce severity of UHIE:
- Albedo (Solar Direct Reflectance): Increasing the SDR of surfaces, primarily roofs, will help reduce heat absorption and subsequent radiation.A TERI (2017 Report) estimated that implementing white roofs across Bangalore City, can reduce energy consumption by 1642 MWh/mtr2/year resulting in savings of Rs. 1,034 crores / year.
- Cool Roofs: Rooftop Gardens – Lawns, Shrubs, Kitchen Garden, can lower heat absorption through the roof and also help in reducing water run-off.
- Vegetation: Roadside Trees, Parks, Vertical Gardens, Rooftop Gardens will help increase green cover across cities. This increase the evapotranspiration effect – which increases humidity levels of the city and in turn increases cooling effect combined with wind. Besides this, vegetation also provides shade across pavements, reducing heat absorption
- Wind Circulation: Increasing height to width ratio between buildings, will enable higher wind circulation patterns which will also help reduce ambient temperatures within the city.
While increasing wind circulation through higher height to width ratio is not possible across existing developed areas in our cities, this can be planned in new development and must become part of the DP of cities. With regards to point 1, 2 and 3 above, combined efforts of city municipality, developers, builders and citizens can help achieve this easily. Additionally, using the right materials that provide long lasting effects is equally critical.
GreenShield™ TPO Roofing membrane is one such product,
that was specifically designed to help mitigate UHI, while protecting buildings
from water leakages at the same time is a sustainable and recyclable product.
GreenShield™ TPO Roofing works in 3 specific ways:
1: Increasing solar reflectance and reducing the absorbance and transmittance of heat below into the roof, resulting in a cool roof that reduces temperatures in and around the building.
2: It is a solid impermeable membrane, thus helping drain off the water from the roof, now allowing anything to leak into the slab
3: Due to high tear and root penetration resistance, it is most ideal for creating vegetative roofs with gardens, shrubs, small plants and trees – enhancing the cooling effect.
GreenShield™ TPO Roof Membrane:
- Solid, impermeable, flexible sheet manufactured and supplied in rolls of:
Thickness: 1.5 mm | Width 2 mtrs | Length 20 / 30 mtrs
- Heat Shielding:SDR: 0.7961 | Emissivity: 0.909 | SRI: 100
- Surface Temperature: 40 oC – high wind conditions, whereas, concrete is at 65oC
(Values as tested at CEPT)
- Easy to install – 10,000 sq.ft. of installation is typically completed within a week*
- Heat Insulation: Due to high SRI, the system provides up to 8oC drop in temperature; lowering HVAC related energy costs
- Weather & Water Proof: Resists UV, Ozone, heat, cold, wet & dry spells of nature – is a barrier against water & moisture
- Protects from corrosion – resistance to chemicals, acids, bases, alkalis, fungi
- Enhances life of roof, protecting it from weathering forces and increasing durability.
- LEEDS / Green Points – Sustainability: Towards, design, construction, operation, maintenance. This sheet is 100% recyclable
- Complies to ASTM D6878, meets US EPA Energy Star requirement, Cool Roof Rating Council (CRRC)
- It is the only system that heat shields and waterproofs at the same time.