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U
U-Value: The
overall coefficient of heat transfer of an assembly measured in BTUs per square foot, per
degrees Fahrenheit difference in temperature per hour.
UBC: Uniform
Building Code.
UL: Underwriters
Laboratories, Inc.
UL Label: A
label that has been stamped on certain materials by authority of Underwriters
Laboratories, Inc. indicating that the material has met certain performance criteria.
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Ultraviolet
Light (UV): A form of luminous energy occupying a position in the spectrum of sunlight
beyond the violet, and having wavelengths that do not enter the visible spectrum. UV rays
accelerate deterioration of roof materials. Hence, the need for protective coatings.
Underlayment: A
material installed over the roof deck prior to the application of the primary roof
covering. Usually consists of fifteen (15#) or thirty (30#) pound organic felt but can
also be self-adhering such as an ice and water protection membrane.
Underwriters
Laboratories (UL): A non-profit agency which functions as the testing arm of the
National Board of Fire Underwriters. It maintains laboratories for the examination and
testing of various devices, systems, and materials to determine their safety against the
hazards of fire, wind, and accidents.
Uplift: See
Wind Uplift.
Upside Down
Roof: See Protected
Membrane Roof.
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