Cool roof waterproofing - Urban heat islands and sustainable cities

Cool roof waterproofing - Urban heat islands and sustainable cities

The phenomenon of urban heat islands is found in cities and describes the temperature difference between urban and rural areas which sometimes reaches up to 4°C. Studies cite that earth’s average temperature will increase between 2 and 4 degrees Celsius within this century. One of the main reasons that contribute to this phenomenon, is the concrete infrastructure and high density-materials found in urban environments and which absorb higher amounts of heat compared to rural areas.  A key factor is the low solar reflectance of urban environments which leads to the absorption of thermal energy and is released later as heat in the environment.

In addition, the use of vehicles, air-condition units and other leads to a further increase in the thermal energy exerted and thus leading to temperature increases. In fact, the use of air-conditioning units is one of the drivers of the worldwide growing energy demand and increases energy consumption at a massive scale in the residential and commercial sectors.

Cool roofs

Roofs are one of the most exposed structures in buildings absorbing a lot of heat. In this respect, cool roofs are considered one of the most sustainable and cost-effective solutions to reduce heat island effect in cities and create at the same time the right thermal comfort in buildings.   

Cool roofs is the term used for roofs that reflect over 65% of the sun’s rays compared to conventional roofs which repel less than 15%. Cool roofs are able to repel heat because the materials used to coat them, offer high solar reflectance.

Studies have shown that the average energy-saving effect of cool roofs ranges from 15% to 35.7% in different climatic zones and the average roof surface temperature reduction is possible from 1.4 ˚C to up to 4.7 ˚C.

The creation of a cool roof improves the energy efficiency of buildings and supports the development in urban sustainability for cooler and healthier environments with better air quality, mitigating the urban heat island phenomenon.


How is the efficiency of cool roofs measured:


The ability of the roofing material to reflect solar radiation.

Thermal Emittance

It shows how long a roof holds onto the energy when the sun heat the roofing material. The thermal emittance ranges from 0-1.


The SRI is calculated based on solar reflectance and thermal emittance in conjunction with ambient air temperature, sky temperature and wind factors. The solar reflective index is reported as a value from 0 to 130 ranging from least reflective at 0 to most reflective at 130.

ALCHIMICA’s advanced roof waterproofing system with reflective materials based on the HYPERDESMO® System offers a SRI value of 102 tested according to ASTM E1980-01 and offers all the benefits of cool roofs.

Thanks to its high solar reflectance the HYPERDESMO® System contributes to the reduction of air conditioning usage which can lessen energy costs up to 15%. Reduction of the urban heat island effect in cities and suburbs, minimizing thermal impact on the microclimate and local environment. High thermal emissivity to release the absorbed heat. Minimizes heat gains inside buildings, improving occupant comfort. Enhances the durability and the appearance of roofs by significantly lowering material temperatures and extending their life cycle.

Explore our system here!


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