The snow removal on a roof in Niigata prefecture

Works on the snow removal on a roof in heavy snow district in Niigata prefecture were reviewed. Now, several methods have been carried out for snow removal on a roof. Above all, snow-sliding method has been widely spread. In order to slide down snow, the houses are roofed with galvanized iron sheets and have less friction with snow cover on them, and therefore, snow cover on them is naturally slided down. However, the sudden falling of an amount of snow has been frequently observed and is very dangerous, after a large amount of snow had been accumulated on the roofs by the freezing between roof surface and snow cover. The coefficient of friction between the roof surface and snow cover is estimated from the accident of the snow-sliding and is smaller than 0.1. The preventive measure against such an accident is to raise the temperature on the roof, for example using planer heaters. Underground warm water is often sprinkled for melting snow cover on a roof, though the water is required to flow uniformly over the roof surface. Also, the circulating system of water, which is collected and warmed by the use of a boiler after sprinkled onto the roof surface was examined. These methods is almost obliged to be interrupted in a few years, because all the houses was damaged by the sprinkled water. It is gradually being popularized to remove snow on a roof with roof heater, so called ′planer heater’. In 1979, roof heaters are attached to the about 60 houses in Nagaoka city, 18 houses in Tokamachi city and 15 in Muikamachi town. It is wasteful and expensible to melt snow cover on the whole surface of the roof, though snowfall is immediately melted even at heavy snowfall. UsuaIly, snow cover on the roof is melted partly. It is the most effective that roof heaters is utilized to let snow slide down. Recently the roof with the korean stove system was built in Tokamachi city and the snow cover on the roof has been removed easily by the korean stove system