Heat insulation has often been seen as something you only do in the cold northern countries and perhaps in the mountains, to minimize the need for heating energy during the cold season. However, experiences from the world’s northern regions have demonstrated that heat insulation also works against summer heat, reducing the need for cooling energy. Therefore, it might be a good idea to add some heat insulation to the walls and roofs of homes and office buildings in the tropics, also.

A few decades ago, it would have been different, because all kinds of electric appliances produced very high loads of waste heat. A single heat bulb consumed 80 – 100 watts of power, instead of the 8 watts which is typical for a modern LED light. A fridge consumed 500 – 1 000 watts, instead of the present 70 – 80 watts. An old-fashioned electric stove consumed two times more electricity than an induction stove.  In other words: adding efficient heat insulation to tropical buildings would have fried the people inside them.

Today so little waste heat is produced by electric appliances that buildings predominantly heat from outside and not from the inside. Human bodies, of course, produce some heat, but it only amounts to an average of 80 watts per adult when a person is resting. In strenuous physical work or exercise the amount of heat produced by a human body can rise to more than 1 000 watts, but most people do not exercise inside their homes during extreme heatwaves.

In the world’s present situation, it would make sense to add some heat insulation to both already existing buildings and new houses.  Hydrophobic insulation materials that could be glued or otherwise installed on the outer surfaces of roofs and walls, ideally under the photovoltaic panels, deserve special attention. One centimetres of simple silica aerogel mat could provide as much heat insulation as three or four centimetres of glass wool.  Simple silica aerogels are becoming very affordable through mostly Chinese mass production, because 99.7 or 99.8 per cent of them consists of air and the rest (0.2 or 0.3 per cent) is silica, which is one of the world’s most common raw materials.

Professor Halimaton Hamdan of the Universiti Teknologi Malaysia was the first to develop high-quality silica aerogels whose raw materials were produced from rice husk at the village level, by rural women’s associations, with special burning chambers designed by professor Hamdan. According to professor Hamdan it would be possible to produce high-quality silica aerogel with the price of 200 euros per cubic metre, using rice husk, containing a lot of silicon, as the resource base. Some mass-produced Chinese aerogels are already getting even cheaper than this.