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Modifying the built environment for global warming—R&D issues
October 2015 became the hottest one on record. Again irrefutable evidence that global warming is a reality. What would be the impact of this on the built environment?
In T&T, there is no need for space heating, being a tropical country, but space cooling has become fairly standard for both residential and commercial buildings. In places like Florida, a semi-tropical climate, the houses are designed for central air conditioning. The same does not apply here and, further, the kind of building materials we use here might not be optimal for energy efficiency.
Most houses here, are constructed using either clay or concrete blocks. A cross-section of any typical wall will be a layer of dried mortar on a layer of clay or concrete followed by an air space and then layers of clay/concrete and mortar respectively.
Air is an insulator and thus once the building heats up, it takes a very long time to cool down. The heat energy contained in the walls contribute significantly to the cooling load and hence a higher electric bill.
To bring this point home, readers are asked to put their hands on the inside of the western wall of their house in the evening. They would be surprised by how hot the wall is. This problem can be exacerbated by the type of paint used.
As the outer wall heats up, the heat flows inwards along the cross section of the wall heating up the trapped air and the inner wall. The inner wall is cooled by both the cool air from the ac unit and the environment outside which is cool at night. The air in the wall, being an insulator, retards heat flow.
In colonial times, to prevent the inner wall from heating up, walls were made of quite thick solid rocks, thick enough for the temperature drop from the outer wall to the inner one to be large enough so that the inner wall was not heated up at all or minimally so. This design meant that the inside of the house was not heated up, it remained cool. This is not the case with the existing hollow bricks that we now use.
If we are to develop energy efficient houses to mitigate the effects of global warming and also to minimise the electric cooling bill, then R&D work must be done to determine the optimal geometric dimensions of bricks required to reduce the heating of the inner wall.
The kind of paint used also has significant bearing on how much the wall heats up from the sun’s rays. Paints that have a low absorptivity will mean that the wall does not absorb much of the solar energy striking it, resulting in a reduced temperature on both the outer and inner sides of the west facing wall. There are many paints on the local market from both local and foreign producers. The thermal parameters of these paints must be available to the public as a matter of course.
Heat transfer is an integral part of any mechanical engineering programme and the determination of the thermal properties of building materials forms an essential component of any energy conservation programme. To design buildings that are energy efficient requires detailed studies to arrive at suitable construction materials and designs for our hot and humid climate.
None of the local universities have any active R&D programme in this area and hence one is needed. It would of benefit to Powergen, T&TEC and the manufacturers of concrete and clay bricks to be involved in and, indeed, to sponsor research in this area.
Some good public education has been done on appraising the public on the merits of switching from incandescent bulbs to fluorescent ones. A similar programme should be embarked upon to educate the public of the benefits of making their homes thermally efficient.
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