U-value


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U-value

[′yü ‚väl·yü]
(engineering)
A measure of heat transmission through a building part or a given thickness of insulating material, expressed as the number of British thermal units that will flow in 1 hour through 1 square foot of the structure or material from air to air with a temperature differential of 1°F.

U-value

A measure of the amount of heat that flows in or out of a substance under constant conditions when there is a 1-degree difference between the air within and outside a building. U-values are used in determining the performance of a glazing system or window assembly.

thermal transmittance, U-value

The time rate of heat flow per unit area under steady conditions from the fluid on the warm side of a barrier to the fluid on the cold side, per unit temperature difference between the two fluids.
References in periodicals archive ?
Figure 2 plots Standard 90.1's maximum wall assembly U-value for seven cities that represent the range of climate conditions in the continental U.S., from cold to moderate to hot-humid to hot-dry.
When comparing U-values, make certain the advertised rating is for the
Case Study Building Envelope and Mechanical System Descriptions (SI Units) Case Wall Roof Glazing SHGC Mechanical No: U-Value U-Value U-Value System Case 0.301 0.227 2.101 0.45 Packaged Rooftop 1 Air Conditioning Units with Gas Heat Case 0.426 0.295 1.987 0.67 4-Pipe Central 2 System with Variable Air Volume Units Case 0.630 0.517 2.839 0.48 Split System 3 Cooling with Gas Fired Boiler Heating Case 0.301 0.256 2.101 0.45 Variable Volume 4 Terminal System with Packaged Rooftop Units 1.
If needed the overall U-value of an enclosure area of interest can be calculated by dividing the heat loss for linear and point transmittances by the overall projected enclosure area.
Ceiling insulation is loose fill cellulose applied to the attic floor to a U-value of 0.0652 W/[m.sup.2]*K (R-value of 87 h.[ft.sup.2.0]F/Btu).
Two levels of labelling are required: (1) a permanent label, word mark, trademark or symbol from a Canadian Standards Council accredited certification organization or an NFRC accredited Inspection Agency that verifies that the product complies with the requirements, and (2) a temporary label setting out the U-value in metric units.
U-value = overall heat transfer coefficient, W/([m.sup.2]*K) (BTU/[h*[ft.sup.2]*F])
After a preliminary search, 14 variables are selected for data mining; they are building age, gross building area, area ratio of office to gross area, area ratio of retail to gross area, area ratio of hotel to gross area, U-value of windows, window glass tinted, cooling capacity, cooling primary energy efficiency, heating capacity, heating primary energy efficiency, building automation system, annual operation time of HVAC system, and total primary energy consumption, as listed in Table 1.
The final design of the building is a cross-shape structure, with light-colored well-insulated exterior walls having a U-value of 0.62 W/([m.sup.2] x K) (0.11 Btu/h x [ft.sup.2] x [degrees]F).