Q. Why should copper roofs be used?
A. Most of the roofs in Japan are made of copper. Historic evidence gives testimony to its durability. The beauty of copper roofs is appreciated in Japan and moreover it suits the climatic conditions too. With time, its beauty enhances.

Q. Copper roofs can be damaged by acid rains.
  .. But does acid rain really fall in Japan?
A. The rain absorbs the carbondioxide in the air which results in the formation of weak acids (pH approximately 5.6.). Rain with a higher concentration of such a pollutant is called acid rain. As per the result of investigations conducted from 1988 to 1992 by the environmental agency, the rains were said to have pH4.5~5.8.

Q. Are copper roofs safe against acid rains?
A. As acid rains have pH4.5~5.8, copper roofs should be totally safe for use in Japan. But even in european countries with stronger acid rains, the industrial buildings' copper roofs have shown no sign of any damage thereby giving evidence of its safe usage.

　
Copper abrasion inspection/Worldwide 48 places:
Average of 4 years from 1986-89
Tokyo 0.0006mm/year
Areas with high sulfuric acid concentration(3-14 times of Tokyo) 0.0014~0.0033mm/year
Okinawa ken 0.0023mm / year
Areas with high salt concentration(2-6 times of Tokyo) 0.0017~0.0031mm/year
Even if the maximum abrasion is 0.0033mm/year, for copper sheets that are
above 0.35 mm in thickness, durability period is more than 60-100 years.
　
　
Q. Do you know that though it is highly durable, its color turns blackish due to rain?
A. The chemical elements or smog in the air dissolve due to rain thereby promoting rapid oxidization of copper, which in turn blackens it. However, when the oxidized film is dark purple in color, on getting washed by the future rains, its color returns to a pleasing light brown after 3 to 6 months.
　
Q. Yet, we hear that bronze statues get damaged by acid rains.
A. Works of art such as bronze statues are complex structures made by unique alloys, external processing and have a combination of various colors. Thus the color becomes oversensitive and changes easily. On the other hand, copper roofs do not undergo color change easily as they are made of pure copper and their form is also simpler.
　
Q. We hear that copper roofs, which are a cultural asset, have also been damaged.
A. The Agency for Cultural Affairs had conducted several investigations in Japan regarding the important cultural asset structures. It was observed that only a few people were in favor of copper roofs. However, these people were those staying in tiled roof structures. Nowadays, the construction manuals are more prudent and there are hardly any technical problems.
　
Q. Concerns regarding acid rain have been vanquished but should we be worried about green rust or copper ions?
A. To say that copper is poisonous is a misconception. After repeated experiments, the Ministry of Health and Welfare has declared copper as harmless to the human body. On the other hand, copper has an anti bacterial effect on certain disease causing bacilli such as colon bacillus. This has been proved by the antigen effect of O-157. Further, copper ions prevent the outbreak of mosquito larva.
　
Q. Yes it is aesthetically pleasing, but the cost?
A. The cost varies as per the form. By calculating the average surface for roofs of general houses, for each construction of 1mｲ, the cost is approximately 15,000-16,000 yens for 0.35mm thick sheets?. Whether this can be termed as expensive is subjective, but, because it is durable and maintenance free, running cost is overlooked. In the long run, copper proves to be the most advantageous material.
　
Q. Who should be consulted for construction?
A. For construction, the designer at the building contractor's office should be consulted. For any further enquiries, please contact the Sheet Metal Industries Association situated in each administrative division of Japan or the Japan Copper Center.