Cool Roofs is a green building technology that is  especially suited to the climate of the India. It is a relatively cheap  option with substantial benefits. Yet you may not be familiar with what  exactly the term means :) So let’s give you a quick primer on Cool Roof  Technology with a special emphasis on its suitability in the Indian  context.

Photo by Iga Palacz / Unsplash

How does a Cool Roof work?

The term itself provides a big clue to its meaning. Cool Roof is a  roofing system that helps keep a building cool. It manages to do this  via two methods

  • reflect away a percentage of the visible, infrared and ultraviolet  radiation from the sun. This reduces the heat gained by the building  itself and is called high solar reflectance.
  • emit away the heat retained by the building. This helps in the  building down quicker as compared to traditional materials and is called  high thermal emittance.

A traditional, dark material roof can reach temperatures of 65oC. Installing an appropriate cool roof technology can bring this down to under 40oC. This is a big difference and results in energy and money savings by using lesser air conditioning.

Great! Tell me more about these benefits.

The obvious benefits to the occupants of a building utilising cool roof technology would be

  • Reduction in electricity bills due to lesser cooling requirement and AC loads.
  • Better indoor comfort for non air conditioned spaces, such as garages, covered patios, garden sheds etc.
  • A possible increase in roof life due to it being subjected to lower than average temperatures.

Additionally, when a high percentage of buildings in an area utilise cool roofs, there are synergistic benefits

  • Reduction in local air temperatures. It can be thought of as the  reverse of the urban heat island effect (maybe call it the urban cool  island effect :P)
  • Lower peak electricity demand, which can help prevent power outages
  • Reduce power plant emissions, including carbon dioxide, sulfur dioxide, nitrous oxides, and mercury, by reducing energy demand.

Roofing solutions for India


Cool Roof Coatings

These can range from a simple limestone whitewash on the cheapest end  to good quality reflective coatings. The price ranges from under Rs 20  per sq ft (for whitewash) to Rs 80 per sq ft (for a good quality  reflective coating)

In addition to high reflectivity, certain coatings also provide  better UV protection and some protection from water and chemical damage.  These additional protections may prove useful if the climate is humid  as well as sunny.

Tiling solutions

Flat roofs can be covered with white or light coloured glazed tiles.  Other tiling solutions also exist for sloped roofs for ex cool shingle  tiles, slate tiles etc. These material may either be naturally  reflective enough to meet cool roof standards or may have coatings  pre-applied to them to increase their reflectivity.

Metal roofs

Metal roofs usually have high reflectivity but are very poor in terms  of thermal emittance. This can be improved by applying cool roof paints  and coatings on these.


Other options


Earthen pots Insulation system

Earthen Pot Roof

This is a traditional method used in India where the roofs (and  sometimes even walls) are covered with upside down earthen pots and then  cemented in place. This traps air between the original roof and the  final surface thus providing insulation. This method helps keep the  building cool in summers and warm in winters.

Green Roofs

By Sky Garden Ltd - Own work, CC BY-SA 4.0

You may choose to install a green roof for your building as an  alternative to cool roof. However the following should be kept in mind

  • They are suitable for urban building with flat roof surface.
  • They can be designed to have basic plant cover to a garden.
  • They are more expensive to implement (as compared to a cool roof solution) and require ongoing maintenance in most climates.
  • They do lower the need for heating and cooling since they provide good insulation and also reduce urban heat island effect.
  • However they are more successful in climates where the heat is not  intense enough to wilt the plant cover or otherwise require additional  protection from heat.
  • Water requirements and drainage is a concern as well and green roofs  may be more suitable in climates with frequent rains and storms.
  • Consulting a professional is highly recommended to get a better idea  of how suitable the building is for such a roofing solution.

Solar Panels

image: iStock

If the conditions on the rooftop are suitable to the installation of  solar panels, this may be considered as an option. However the cost to  install this is 10 to 50 times higher as compared to a cool roof  solution so it is usually only considered by institutions and industries  if at all.


Should I install a cool roof for my building?

The honest answer is that it depends on a number of factors. However  as a rough guide, given the long and very hot summers in the Indian  subcontinent, there is a good chance that you’ll benefit from a cool  roof installation. Some of the factors that you should still consider  are

  • What is the climate like? How much sun does the roof get? The greatest savings are seen in hot climates while cold climates might see an increase in their heating bill.
  • Humidity. In warm climates with a higher humidity,  cool roofs are more prone to mold and fungal growth due to lower  temperatures. Thus coating that protect against moisture and include  microbial protection should be selected. In cooler climates with high  humidity, cool roofs are more prone to condensation and thus proper care  must be taken with the roof design to mitigate these issues.
  • Is the building still in the planning phase or has already been constructed? There is more leeway in choosing a roofing solution if the building is  still in the planning phase. The solutions available for existing  buildings are somewhat restricted in comparison.
  • Condition of the roof. It makes less sense to go  for a cool roof solution if the existing roof is relatively new and in  good condition. This is because a big chunk of the cost comes from the  specialised material and labour involved in the installation. It may be  better to pick solution requiring more specialised labour and materials  if the roof requires repairs anyway so that the investment can be  defrayed against regular maintenenance.

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