What roof is better?
Usually, choosing than to cover the new house, owners pay attention to a design of a roof and a roof material. But according to the American researchers, color is not less important. Esthetic appeal of the dwelling, a condition and life cost depends on it in it.
Estimating economic expenses and benefits from three various types of roofs, scientists from Berkeley Laboratory (Lawrence Berkeley National Laboratory) tried to find out, what of them are suitable for construction and accommodation more. The attention of researchers was involved by black, white and green (vegetative) roofs.
As it appeared, at a 50-year cycle of operation roofs of white color are most economically effective. At the same time, though high cost of arrangement turns them into «expensive pleasure», ecological and household advantages of green roofs partially compensate financial loading.
In the report published on the Internet «Economic comparison of white, green and black flat roofs in the United States» researchers presented direct economic comparison of the listed types. According to one of coauthors, the honourable commissioner of the Californian power commission Arthur Rosenfeld (Arthur Rosenfeld): «White roofs win, proceeding from purely economic factors, production of black roofs should be stopped».
In the report 22 commercial projects of flat roofs in which not less than two types of a roof are used are considered. Researchers analyzed 50-year life cycle, including term of operation of white and black roofs to equal 20 years, green – 40.
Green roofs which often call vegetative, or roofs gardens, become in recent years more and more popular choice of the Americans, based on esthetic and ecological advantages. For example, such roofs provide effective management of storm drains, helping to avoid sewerage overflow, cool a surface of overlappings and clear air. Besides, green roofs are a source of esthetic pleasure, please the eye and cheer up inhabitants.
Researchers recognize that the listed advantages were not considered at work on the report. «We left open possibility of that other factors can make green roofs more attractive and more favorable options under certain conditions, – the coauthor of the report Benjamin Mandel (Benjamin Mandel) told. – The relation of expenses and benefits actually changes in accordance with the circumstances».
In the general opinion of researchers, green roofs do not compensate climate changes, unlike white which reflect approximately three times more sunlight that promotes smaller absorption of energy by a planet surface. Absorbing less light, than green or black, white roofs partially compensate effect of warming as a result of effect of hotbed gases. «White and green roofs well do the part, cooling buildings and air in the city, but white roofs are three times more effective in fight against climate changes, than green roofs», – Rosenfeld argues.
As to black roofs, scientists consider them dangerous not only for climate, but also for human health. In hot weather they become a major factor of risk for inhabitants of the top floors.