The SI unit for period is the second. For counts per unit of time, the SI unit for frequency is hertz (Hz), named after the German physicist Heinrich Hertz; 1 Hz means that an event repeats once per second.A previous name for this unit was cycles per second (cps).or each dot, f is the frequency in hertz (Hz) â meaning the number of times per second (i.e. cycles per second) that it flashes â while T is the flashes' period in seconds (s), meaning the number of seconds per cycle. Each T and f are reciprocal.
Photo: CertainTeed. Economical to produce, relatively easy to install and widely available, asphalt shingles are todayâs most popular roofing materialânot only because theyâre less costly than wood, wood shakes, tile, metal or slate, but also because their guaranteed life span pits them favorably against competitors.
Composite roofing. Most people are familiar with composite roofing, one made up of an arrangement of composite shingles. Easy to install and available in various brands, materials and colors, composite shingles are a very popular choice for home builders.ome back and see us again soon! With roofing prices shooting sky high, it's no surprise that homeowners want to make the most informed decision before investing. While many roofing materials exist, a common debate in residential roofing is that of metal roofing vs. composite roofing.