The roof of a building is exposed to direct sunlight, which raises the surface temperature more than expected.

The roof of a building is exposed to direct sunlight, which raises the surface temperature more than expected.
In summer, temperatures can reach 70-80°C, which reduces the cooling efficiency of the building's interior and increases energy consumption.
It also contributes to the heat island effect in large urban areas.
Rooftop greening is attracting attention as a means of improving these problems, but often requires renovation work due to waterproofing measures and building strength issues.
This is where highly heat-shielding paints come in.
Since Nagashima Specialty Paints began producing and selling high heat-blocking paints in 1997, we have steadily built up a track record in the field of high heat-blocking paints, from offices and factories, where energy conservation is required by the revised Energy Conservation Law, to roofing materials for general housing.
We have developed highly heat-shielding paints in line with our business development to date. It is said that the factor that causes the temperature inside a building to rise is the surface temperature of roofs and exterior walls heated by sunlight and transmitted indoors, which is greater than the effect of outside temperatures.
High thermal barrier paints contain inorganic ceramics and other materials in the paint that effectively block wavelengths in the thermal and infrared regions, preventing heat buildup on roofs and exterior walls.
First commercialized in 1984 by ThermoShield Corporation of the U.S., they have been sold in Japan since the mid-1990s, mainly through imports.
In 1996, Nagashima Specialty Paints formed a partnership with ThermoShield of the U.S. and developed its own highly heat-blocking paint.
Since its establishment, the company has consistently manufactured industrial specialty paints such as gasoline-resistant urethane paints, rubber and leather paints, luminous paints, and UW paints.
The company's motto is "to develop paints that improve the quality of painted products, reduce the environmental impact of the paints themselves, and do not impair productivity.
Noriyuki Fukae, Director and General Manager of the Functional Coatings Division, says, "Our theme is how to provide a variety of functions within the unit of micrometers.
Miracle, which combines excellent thermal barrier effects with cost competitiveness, is made of spherical ceramic grains (silicon hollow ceramic balloons) with a diameter of 20 to 100 microns and a nearly vacuum center, blended in the dry coating film at a ratio of 40 to 60% by volume.
Although easy to mix and hear, the specific gravity of ceramic grains is as light as 0.2, so special techniques are required to disperse them uniformly in the paint before drying and in the paint film after drying.
The company's know-how has made it possible to create a product that is as easy to pack and work with as ordinary paints.
Special coating equipment is not required, and installation costs, which are the most expensive part of the coating process, are the same as those for general paints.
In addition, when it comes to heat shielding, people tend to think that reflecting sunlight will suppress the temperature rise, but in reality, the long emissivity (the ratio of absorbed heat released to the outside) and heat conduction also have a great deal to do with it.
For example, aluminum materials used for roofing have a high reflectance of 90%, but its long-range emissivity is only 10%.
In other words, the 10% heat that cannot be reflected accumulates rapidly.
In the case of Miracleur, the reflectance varies depending on the color, but for example, the basic color, white, has a reflectance of 90%, which is as high as aluminum, and a long-wave emissivity as high as 94%.
The ceramic mixture creates fine bumps on the surface, which increases the surface area and thus the amount of heat emitted.
The hollow ceramic also suppresses heat conduction into the room.
The combination of these three effects of reflection, radiation, and conduction is the key to the high thermal barrier properties.
If compared in terms of life cycle, it is also cost-competitive compared to ordinary paints.
Currently, Miracle is available in two types of weather-resistant paints: Miracle S100, which uses silicone resin, and Miracle F200, which uses fluorocarbon resin for even greater weather resistance.
The price of Miracle S100 is 1.5 times that of ordinary silicone resin-based paint, and the price of Miracle F200 is 1.2 times that of ordinary fluoropolymer-based paint, so the price of the paint itself is still high.
However, installation costs are the same as for general paints, and cost reductions can be expected through energy savings.
Another advantage of this product is its longevity, which is higher than that of ordinary weather-resistant paints because the coating film does not deteriorate due to thermal contraction caused by reflection and heat dissipation.
There are high expectations for the product's expansion into the Southeast Asian market, with approximately 250 installations already underway.
At the moment, demand is mainly for use on warehouse roofs to improve the working environment inside buildings and to maintain the quality of stored goods.
Annual production of Miracleur is about 500 tons and is increasing at a rate of 1.5 times per year.
In the case of companies that have several factories, the number of cases where one factory has tried Miracle and found it to be highly effective is increasing, leading to the installation of Miracle on other factories as well.
One factory that decided to renovate its warehouse for chemical storage was considering installing air conditioning to prevent the room temperature from rising above 30°C (86°F).
However, by applying a high thermal barrier coating, the factory was able to reduce the number of air conditioners by half compared to the original plan.
As a result, not only were the purchase and running costs of the air conditioners reduced, but also cost benefits were gained, such as eliminating the need for additional power receiving equipment due to increased power consumption.
In addition, the system has recently begun to be adopted not only in Japan but also at Japanese-affiliated factories in Malaysia, Thailand, and other Southeast Asian countries.
The benefits are even greater than in Japan because of the strong direct sunlight throughout the year and the high cost of electricity compared to commodity prices.
Although there are still few examples of applications in general housing and condominiums, it is said that as a side effect, applying the coating to the floor of a balcony can bring reflected light into the room and reduce the amount of lighting near the window.
Furthermore, there are some interesting examples of applications, such as coating the roofs of buses and the Nozomi bullet train, and more applications are expected to come.
One of the applications we are focusing on is gas tanks," says Fukae.
Gas tanks have a double-layered structure and a large amount of insulation material is used inside because thermal contraction due to temperature rise can cause cracks in the joints.
High thermal barrier coatings could reduce the risk of cracking and reduce the amount of insulation used.
Similar principles are expected to be employed in fuel oil and chemical storage tanks.
In an experiment using a highly heat-shielding paint on a refrigerator designed to be a vending machine, it was reported that the paint reduced the refrigeration load by 10% on average over an hour.
There are approximately 2.6 million beverage vending machines installed throughout Japan, making it an attractive market.
Demand for these and other applications will no doubt continue to grow as a response to the Energy Conservation Law, which has expanded the scope of its coverage, and as an element of continuous improvement, which is becoming a growing concern for companies that have acquired ISO 14001 certification.
Although not as visually effective as rooftop greening, the range of applications is wide.