Whitewashing rooftop can take the edge off summer heat

By April 5, 2016General

Thiruvananthapuram: Since 1950s, reinforced cement concrete (RCC) roofs are common in Kerala. It continues so despite its major drawbacks of increased room temperature, corrosion and water leaking. In the scorching summer of Kerala, flat RCC roofs turn into a bane for dwellers as they absorb more heat, increasing the room temperatures beneath them.

In this context, experts at Centre for Innovation in Science and Social Action (CISSA) here suggests that a cheaper way to bridle the soaring temperature is to paint white your RCC rooftop’s flat surface exposed to sun. This can reduce room temperatures by 3 to 4 degree avows a team of experts at CISSA.

The total temperature felt inside a room is due to heat radiated from the atmosphere outside and living and nonliving objects inside, including body temperatures of people and burning bulbs. Out of these, the heat radiation due to atmospheric temperature can be controlled by white washing the terrace floor.

Albedo coefficient

Reflectivity of a surface is measured by a coefficient called albedo. If albedo is zero, no part of the sunlight falling on it is reflected back. Such surfaces accumulate heat. Whereas, surfaces with albedo value 1 has maximum capacity to reflect the sunlight, thereby minimizing the accumulated heat.

When the floor of the terrace exposed to sunlight is painted white, the albedo value increases and good part of the heat due to sunlight gets bounced back. Consequently, the roof’s heat conductivity is considerably limited.

Blackish surfaces have got near zero Albedo value, gathering radiations falling on it, turning the roof into a reservoir of heat. “This summer is precise time for us to first remove the dry algae that gives a blackish tint for our terrace floors. Clean it with a broom, wash it perfectly and paint the surface white for reducing the room temperature beneath by at least 4 degrees”, suggests Suresh Babu, energy consultant at CISSA who is an accredited energy auditor with bureau of energy efficiency, Ottotractions.

He himself has tried it out successfully at his office building in the city. Not over, he could inspire 20 more building owners to try out with the magic of white, to get recognised by Earth Day Network, an international movement for earth’s conservation.

Urban heat islands

With temperature of earth increasing due to multiple reasons, our urban pockets are becoming heat islands. “This means, if you take a thermal imagery of urban spaces, there will be many a number of islands serving as heat generators. Major reason is the structures that collect sunlight than reflecting it”, Mr. Suresh Babu says. Hence our efforts to cool the RCC roofs have got a significant environmental role, he adds.

“Reducing room temperature has got manifold benefits. First of all, your living comfort; then reducing the use of electrical appliances meant for regulating room temperature”, he reminds.

Coconut leaves not a solution

Experts caution that using coconut leaves for covering the exposed roof cannot be a solution. “First of all, as days pass, coconut leaves turn brownish and then blackish, adding to albedo effect. The issues of its availability and labour are extra”, say experts.  About people trying with collecting water on their roofs, experts warn that in the present climate it may prove detrimental to the roof’s sturdiness, producing blisters and cracks.

“Cleaning rooftop’s exposed floor and painting it white is something that must be manageable for the family members during their free time”, they say.  Experts at CISSA suggest that unless the roof has got severe breakage and probability of leakage, one should not go for costly surface coats. Cheaper white cement and primers are more than enough for protecting normal roofs this summer.

For free expert guidance in this regard, contact CISSA at phone 0471 2722151, 9447068747.White wash (1) White wash (2)

One Comment

  • Kannan says:

    If Rain water harvesting is done, will not the rain water carry chemicals from the painting to the sump or well, which is used a potable water?

Leave a Reply