• Shrinking plots, dense construction push traditional passive cooling features aside
• Concrete surfaces, poorly insulated roofs, western-facing windows intensify indoor heat
• Experts urge climate-responsive design, natural ventilation, stronger construction standards
• Loss of wetlands, mature trees, urban greenery strips cities of natural cooling systems
• Calls grow for mandatory green-space requirements in urban development
• Climate-resilient construction brings higher upfront costs but could reduce reliance on air conditioning

Sri Lanka’s cities and suburbs are becoming densely populated, with concrete structures, paved surfaces, and shrinking green spaces altering not only the appearance of urban areas but also their resistance to heat. 

As temperatures rise and extreme weather becomes a growing concern, questions remain as to whether the way modern Sri Lanka designs and constructs homes and cities is equipped to keep people cool and comfortable. 

Traditional Sri Lankan homes were designed with characteristics like verandas, courtyards, clay-tiled roofs, and thick walls, which suited Sri Lanka’s tropical climate. Natural ventilation and surrounding green spaces, such as trees, wetlands, and gardens, contributed to cooling the interiors. However, modern-day factors such as smaller land plots, rapid urbanisation, and modern building techniques are altering these traditional approaches to home design. 

Speaking to The Sunday Morning, experts from the environmental, architectural, and construction sectors highlighted the need to rethink urban planning, designing, and construction regulations to keep our cities and suburbs cooler and weather resilient.

Architectural lens: Old vs. modern houses

Sri Lanka’s traditional architectural features that help homes remain naturally cool are becoming increasingly difficult to incorporate as urbanisation, smaller plots, and a growing reliance on air conditioning reshape residential construction, according to PWA Architects Principal Architect Philip Weeraratne. 

Weeraratne explained that traditional Sri Lankan homes included various passive cooling elements, such as extended roof eaves, clay tiles, courtyards, thick laterite walls, and verandas, which helped protect structures from direct sunlight and facilitated natural ventilation. 

“Traditionally, we had eaves, where the roof extends over the wall and extends out to protect the walls from the direct effect of sunlight,” he said. 

He noted that traditional clay-tiled roofs also helped reduce heat entering homes, while central courtyards were designed to facilitate cross-ventilation. “Traditional Sri Lankan houses had centre courtyards where the wind could blow through the house. There was a lot of thought given to cross-ventilation, so that the wind would blow through the house and go out through the courtyard.” 

According to Weeraratne, the use of thick laterite walls and verandas further contributed to thermal comfort by limiting the amount of heat reaching the interior of homes. He said that the larger plots available in the past also allowed homes to retain more vegetation, while past cities had fewer paved and concrete surfaces that contributed to heat accumulation. 

“Because the plot sizes were bigger, each house had much more greenery and trees around. The cities were not so full of tarred roads and concrete, so the heat levels were low. There were many trees that captured the breeze and they provided a lot of shade to houses,” Weeraratne said. 

However, he added that rapid urbanisation had significantly reduced the amount of greenery surrounding houses, with gardens increasingly being replaced by buildings. As a result, he noted that the ability to incorporate traditional passive cooling approaches had become increasingly restricted. 

“We are now forced to adopt more modern methods of construction,” Weeraratne said, adding that architects were increasingly relying on measures such as insulation, appropriate window orientation, and verandas where space allowed. 

Still, he noted that such traditional approaches were becoming increasingly difficult to implement due to the shrinking size of residential plots, particularly in urban areas. “Unfortunately, in today’s day and age, we have to build on very tight blocks of land. Therefore, we are limited in our ability to construct eaves or centre courtyards,” he said. 

The increasing use of air conditioning has also influenced the way modern houses are designed, according to Weeraratne. Homes designed for air conditioning generally require more enclosed spaces to prevent conditioned air from escaping, limiting opportunities for natural ventilation. 

“When a home is being designed for air conditioning, very little consideration can be given for cross-ventilation because the house has to be completely sealed and almost airtight to prevent the conditioned air from escaping,” he said. 

Nonetheless, Weeraratne stated that architects may still incorporate climate-responsive elements into modern homes, including carefully considering the orientation of buildings and the positioning and size of windows. 

He identified windows exposed to the western sun, insufficient shading, and poorly insulated flat roofs as some of the key design challenges contributing to excessive heat inside homes. He further pointed out insufficient overhang above windows and the inability to construct sheltering spaces such as verandas or to allow functionally similar buffer zones between the interior and exterior as being among the challenges. 

Weeraratne also warned that uninsulated concrete roof slabs could allow substantial amounts of heat into homes. “Flat roofs and concrete slabs without proper insulation allow a massive amount of heat to penetrate the slab,” he said, noting that insulation was therefore increasingly being incorporated into modern residential designs in order to reduce heat transfer. 

Weeraratne also stressed the importance of greenery in and around buildings, stating that architects should attempt to incorporate vegetation wherever possible. “It is essential to have green spaces, so we try to bring in as much greenery into our projects as possible,” he said. 

He added that this may include interior gardens, vertical gardens, trees, and rooftop gardens, although the extent to which greenery could be incorporated ultimately depended on the preferences of individual homeowners. “We, as architects, definitely advocate a lot of greenery – horizontally, vertically, and on top of buildings.”

However, Weeraratne noted that some homeowners were reluctant to maintain vegetation due to concerns about mosquitos, falling branches, upkeep requirements, and a lack of gardening time. 

Moreover, he stated that professionally designed homes generally took heat and changing weather patterns into consideration, although challenges remained where buildings were designed by people without adequate architectural training. 

He added that the major limitation for architects remained the constraints imposed by increasingly dense urban environments. “The biggest constraint is working in an urban space. In such a scenario, there are limitations in relation to the number of things that can be done.”

Weeraratne also pointed to emerging technologies that might improve the thermal performance of buildings, such as heat-reducing glass, specialised paints, improved window systems, and natural cooling solutions. “There are several new technologies that have been developed. However, we will have to wait for a while until they become affordable enough to be used in our buildings as well,” he said.

Construction: Building against the heat

Although the materials used in Sri Lankan homes can have a big impact on indoor thermal comfort, construction experts advise that when building homes that can withstand rising temperatures, the design of the house, especially its ventilation system, should be taken into account, in addition to the choice of materials. 

Hello Builders Ltd. Managing Director Eng. Ranga Kasturi Arachchi noted that concrete remained the dominant structural material in Sri Lankan housing, but its thermal properties could contribute to heat entering buildings. 

“Almost 90% of house construction uses concrete. Concrete is a heat-conductive material. You definitely get enough and more heat from the environment through concrete,” Kasturi Arachchi said. 

He added that cement blocks were also increasingly replacing bricks for partition walls, largely due to the cost and availability of bricks. 

“Currently, most industries are moving towards using cement blocks, whereas two decades ago, for instance, most constructions including high-rise apartments used bricks. We no longer have enough bricks and the quality of bricks has also deteriorated due to increased costs. Therefore, cement blocks are most commonly used, but they have high thermal conductivity compared to bricks,” he explained. 

Roofing materials could also make a difference, Kasturi Arachchi said, noting that higher-budget and luxury homeowners often opted for clay-based tiles such as Calicut or Roman tiles instead of asbestos sheets because of their comparatively low heat conductivity. 

However, he stressed that homeowners should not focus solely on choosing construction materials when attempting to make a house more climate-resilient. “A house owner should [focus on having] a proper design rather than selecting the material.”

Kasturi Arachchi stated that proper cross-ventilation, natural lighting, and ventilation should be integrated into the design from the start, allowing residents better thermal comfort without relying entirely on mechanical cooling.

“My recommendation is that a house owner should hire a proper chartered architect or institution to build their house in a manner that ensures more natural ventilation and light, rather than selecting material, although material selection is important,” he said. 

Meanwhile, P.V.H. Perera of Mudannayake Construction noted that Sri Lankan construction generally used materials capable of withstanding the country’s hot weather, with bricks and blocks being the most commonly used materials for walls. 

He added that plastering also helped reduce the amount of heat felt inside a building. For roofs, Perera said there were several materials available that were meant to prevent heat from being transferred directly into a house’s interior, instead reflecting some of the heat away from the building. 

However, he added that certain construction practices could make homes more vulnerable to heat. “Using normal asbestos sheets for the roof is not good,” he said. 

Perera also suggested maintaining a gap between the roof and the rest of the house and using thicker wall construction where possible. “The walls should ideally be wider and thicker. If possible, it is better to build the walls using two layers of bricks,” he said, explaining that this could reduce the amount of heat entering the home. 

However, he added that the higher cost of bricks was one reason why they were not being used as frequently. 

Both construction professionals agreed that building a more climate-resilient home could involve higher upfront costs compared to conventional construction, noting that climate-resilient construction was more common in urban areas.

Cities losing natural air conditioning

Environmentalists have advocated for stronger urban planning measures to preserve green spaces, wetlands, and waterways as rapid urbanisation and expanding concrete infrastructure contribute to rising temperatures in Sri Lanka’s cities and suburbs.

Centre for Environmental Justice (CEJ) Chairman Hemantha Withanage stated that the rapid loss of wetlands around Colombo was one of the primary factors contributing to cities becoming increasingly hot. 

“Colombo is a wetland city. But unfortunately, instead of preserving these marshlands, we are destroying and filling them,” he said, pointing to areas including Maligawatte, Battaramulla, and Kolonnawa, which had once contained extensive marshlands. 

He stated that urbanisation had accelerated particularly around Battaramulla following the construction of the Parliament Complex, resulting in the rapid development of areas that had previously been wetlands. 

Withanage also pointed to the loss of mature trees along roadsides and in urban areas as a major concern. “You can still find large trees on Bauddhaloka Mawatha surrounding the United Nations office, but in most [other] areas, such big trees have disappeared,” he said. 

According to the CEJ Chairman, the increasing concentration of high-rise buildings, concrete structures, roads, and vehicles is contributing to heat accumulation in urban areas. “When you have concrete buildings, everything around them becomes very warm,” he said, adding that the growing number of vehicles also contributed heat and emissions to the urban environment. 

He explained how concrete and asphalt may absorb heat throughout the day and release it later, resulting in warmer surroundings, especially at night. “Concrete structures normally absorb heat and release it into the environment,” he said. 

Withanage added that alternative construction methods, such as hollow concrete blocks and other building technologies, could potentially help improve thermal conditions, but noted that their usage and adaptation remained limited. He said that green roofs and rooftop gardens could provide one possible solution as high-rise construction continued to expand.

“High-rise building construction cannot be stopped, but having trees or plants in these buildings and on rooftops is one solution,” he said, citing examples from European towns where vegetation had been incorporated into relatively modest urban places, including structures such as bus stops.

However, Withanage stated that Sri Lanka lacked proper planning for urban greenery and instead advocated a more scientific approach to tree management. He said that trees were often removed due to concerns about falling branches during severe rain and cyclonic conditions, rather than being properly maintained or pruned. “There should be a scientific approach to planting trees and cooling the city,” he said. 

At the policy level, the CEJ Chairman called for minimum requirements for green spaces to be incorporated into urban development and individual building projects. “There should be [adequate] green spaces compared to the population and the developed area, which cannot be converted into construction sites and building structures,” he said. 

He suggested that regulations or guidelines should obligate individual structures and buildings to maintain a certain amount of green space, noting that some green-building guidelines already included similar provisions, although questions remained over their implementation. 

Withanage also emphasised that improving urban resilience should not be limited to Colombo, noting that cities such as Kandy and Galle were also undergoing rapid urbanisation. However, he stated that cultivating greenery was not always practical for individual residents, particularly those who lived in densely populated areas. 

“It’s not possible for many people to plant a tree in their own home garden as it isn’t practical,” he said, arguing instead that residents should collectively demand the preservation and creation of small green spaces within urban areas. He added that such spaces did not have to be large parks, but instead could be small patches of greenery that supported birds, butterflies, and bees. 

Withanage also called for greater public responsibility in preventing vacant and green spaces from becoming dumping grounds. 

Another key concern, he said, was the condition of Colombo’s waterways and canals, which were increasingly affected by garbage and pollution. “If people are educated on such matters and the necessary laws and regulations are introduced to ensure [responsible] behaviour, Colombo can be clean and so can the water,” he said.

Ultimately, Withanage stated that creating cooler and more resilient cities would require both stronger planning and a change in public attitudes. 

“My advice is that the public must collectively demand green spaces in Colombo and all other major regions,” he said, adding that keeping waterways clean should also be viewed as “everyone’s responsibility, and not only of the local authority”.