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Glossary of Roofing Terms - U

UBC: Uniform Building Code.

UL: Underwriters Laboratories Inc. (which see).

UL Label: See UL Mark.

UL Mark: (From the UL website): The UL Mark on a product means that UL has tested and evaluated representative samples of that product and determined that they meet UL requirements. On roofing materials, the UL mark is typically found on a label that has been affixed to the material’s packaging.

Ultraviolet Light (UV): A range of electromagnetic radiation with a frequency higher than visible light, but lower than X-rays. UV rays contribute to the breakdown of chemical bonds, and thus can cause the deterioration of many types of roofing materials. Asphalt is at particular risk of UV degradation due to the length and instability of the molecular chains comprising the material. The prevention of UV degradation is the primary reason for the protective surfacing applied to bitumen-based roofing materials.

Undereave: See Soffit.

Underlayment: A sheet material applied directly over the roof deck before the installation of the roof system. Underlayments function in various roles, including air barrier, vapor retarder, protection against ice dams, and as a secondary water barrier.   

Underwriters Laboratories (UL): An OSHA-approved independent product safety certification organization. It operates laboratories devoted to the testing, evaluation, and certification of a wide range of commercial products, assemblies, systems, and materials.

Uplift: In the context of roofing, Wind Uplift (which see).

Urban Heat Island Effect: From the EPA website: “The urban heat island effect is a measurable increase in ambient urban air temperatures resulting primarily from the replacement of vegetation with buildings, roads, and other heat-absorbing infrastructure. The heat island effect can result in significant temperature differences between rural and urban areas.”

Urethane: See Polyurethane.

U-Value: A term used in building science to refer to the overall heat transfer coefficient of a building component, i.e., a description of how well the component conducts heat.

UV Degradation:  Damage done to a material at the molecular level by ultraviolet light.