The flat roof of the building is exposed to the hot summer sun for the longest time of the day. It is natural for the roof to be heavily heated. As the heat is transferred below, the rooms below them also become unbearably hot. How can we avoid or reduce this kind of heat?

This is the logic of the cause and the remedy. Concrete is a very dense material. When concrete is heated, it retains heat for a long time. When the surrounding environment gets cooler, this heat will radiate into the room at night. Since the air under the roof is still, the air in the room also becomes very hot. A ceiling fan rotating under the roof pushes the warm air downward. Needless to say the discomfort.

Prevent the roof from getting hot

Insulate the roof from above

Insulate the roof from below

Avoid heat transfer from the roof to the room

Use some methods to cool the roof

Extract the hot air collected under the roof

Extract heat from the roof before heat transfer

If the heat of the sun cannot stand, we stand under a tree or open an umbrella to shade it. We also experienced that the temperature in a house shaded by trees is very low and pleasant, even in summer. We parked the car under a tree to prevent it from getting hot. Similarly, if sunlight is heating the roof, use a lightweight roof made of GI Sheet, Mangalore Tiles or canvas for shade. The shading prevents the roof slabs from heating up. The shelter can also be used for gatherings.

The roof can also be shaded by a shading function like a pergola. Vines can be planted on the pergola to add shade.

The high walls or lattices around the roof can also cover the roof. However, this will be a costly thing.

Plants are the best material for sheltering the roof. Unlike tin roofs, plants are not heated. They absorb heat and light. Put potted plants on the roof, shade the roof and enjoy the vegetables they produce. Make a terrace garden.

The top floor of the apartment is the service floor, which contains overhead water tanks, pressure pumps, elevators, electrical panels, CCTV cameras, access control monitors, fire safety equipment, water tanks, etc. It doesn't matter whether this floor is heated or not. It can definitely prevent the last living floor from getting hot.

The terrace garden will prevent heat absorption. Plants and grass shade the roof. The earth will insulate the roof. The humidity in the mud will definitely cool the roof. However, if the roof can carry the garden load, please consult your structural engineer and consult a landscape architect to design an easy-to-maintain garden.

Traditionally, "Surkhi" is a weatherproof layer made of bricks, lime, maravajra (natural binder) and Antvalakai (chewing gum) to prevent the roof from heating up. Due to lack of skills and know-how, it is not popular now. Weather-resistant clay boards are usually used for insulation. Each clay panel has three tubular holes.

This gap helps to avoid heat transfer. In addition, clay does not absorb and retain too much heat. It is laid on the concrete roof with cement mortar.

Foamed concrete slabs can be used in a similar way instead of the above-mentioned clay slabs. The spongy perforations in the lightweight concrete block prevent heat transfer to the roof slab.

A layer of 40 mm gravel (railroad jelly) on the roof can effectively prevent the roof from heating. Gravel shelters the roof during the day. The polygonal surface of the gravel has minimal contact with the roof. This can prevent heat transfer. At night, the gravel releases heat into the cool air. The disadvantage of this remedy is that we cannot walk comfortably on the roof to use the terrace.

In Jodhpur, Rajasthan, the roof is painted white with lime. White lime reflects a lot of heat, which would otherwise be absorbed by the roof. However, the top must be painted almost every year.

Many manufacturers use the same technology and provide roof coatings that can last for many years. Although some coats are white, others are silver to improve reflectivity. The supplier claims that the heat has been reduced by 5 degrees.

An asphalt board with a silver coating on one side can be used for the top insulation of the roof. They not only reflect heat and heat insulation, but also prevent roof leaks.

They are about 8 mm thick and have a silver coating on the exposed side. They stick to the roof with bituminous liquid. The silver coating reflects heat and the asphalt is insulated.

In buildings under construction, insulation materials can be installed on the roof. Hollow clay slabs and lightweight foamed concrete slabs can be used as roof fillers. This type of roof is called a "filled board" roof.

This technique has 3 advantages. The amount of concrete is reduced, the load on the structure is reduced, and the increase in heat on the roof is controlled.

(The author is a practicing architect in Bangalore)

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Printable version | December 8, 2021 at 2:11:54 AM | https://www.thehindu.com/life-and-style/homes-and-gardens/keeping-your-house-cool/article17441767.ece

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