Definitions - u


U-value applies the factor of time to the heat-loss measurement. U-values measure heat that escapes per hour through a window. Windows typically have two U-values: one for the glass and one for the window, including the frame.

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Underfloor Heating

Underfloor heating is where the method of heating a room is provided through the floor. In essence a heating element, be it electrical or water based is embedded into the floor during construction. Then when heat is required in the room this is turned on to slowly heat the floor itself, which then raises the temperature in the room.

The big advantage with this approach is there are no visible evidence that the room is heated (i.e. vents, A/C units, etc) - keeping things very neat and tidy. The other big plus is with the floor being heated it is actually warm to walk on bare foot.

The downside is that you can only really do this well with tiled floors as you need a good heat conductor immediately above the elements. Also it is not 'instant' heat rather it will take a good hour to get up to temperature in most cases.

Although given the high thermal mass of such a floor, you can use this to your advantage by heating the floor during 'off-peak' times to then slowly release the heat during the following day.

If set up correctly in a well insulated property, underfloor heating can be quite cost effective. 

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Underground Injection

A method of land disposal in which liquid wastes are injected into known geological formations, generally at great depths.

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Unfinished Oils

All oils requiring further refinery processing, except those requiring only mechanical blending. Includes naphtha and lighter oils, kerosene and light gas oils, heavy gas oils, and residuum.

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Uniform Region

A territory with one or more features present throughout and absent or unimportant elsewhere.

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Upgradeable Product

The ability to increase a product’s performance or features without replacing the product.

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The upward flow of cold, nutrient-rich water toward the ocean surface as currents or seasonal winds draw warmer water away from a coast. Phytoplankton that feed in upwellings often support huge fish populations.

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Urban Heat Island
Buildup of heat in the atmosphere above an urban area. Often caused by an inversion with associated smog.

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