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(ˈyuˌvæl yu)

a measure of the flow of heat through an insulating or building material: the lower the U-value, the better the insulating ability. Compare R-value.
[1945–50; U, symbol for internal energy]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
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Figure 3 plots the Standard 90.1 maximum roof U-value over the period during which Standard 90 has been in effect.
Windows are assigned a "U-value" measuring how much heat is
Case Study Building Envelope and Mechanical System Descriptions (IP Units) Case Wall Roof Glazing SHGC Mechanical No: U-Value U-Value U-Value System Case 0.053 0.040 0.37 0.45 Packaged 1 Rooftop Air Conditioning Units with Gas Heat Case 0.075 0.052 0.35 0.67 4-Pipe Central 2 System with Variable Air Volume Units Case 0.111 0.091 0.50 0.48 Split System 3 Cooling with Gas Fired Boiler Heating Case 0.053 0.045 0.37 0.45 Variable Volume 4 Terminal System with Packaged Rooftop Units 1.
Analysis of logarithmic mean temperature differences (LMTD) (approach temperatures at inlet and outlet) and overall heat transfer coefficient (U-value) shows that the performance of the EA cooler has improved.
For each linear or point thermal anomaly (slab, shelf angle, parapet, beam, etc.) the thermal transmittance for the whole assembly (U-value) was compared to the thermal transmittance without the thermal anomaly (clear field value, [U.sub.0]).
Cavity bays are filled with fiberglass insulation to a U-value of 0.115 W/[m.sup.2]*k (R-value of 49.2 h.[ft.sup.2.0] F/Btu).
* Window U-value [less than or equal to] 0.8 W/[m.sup.2]/K (0.14 Btu/h/[ft.sup.2]/ [degrees] F)
ENERGY STAR sets standards for windows based on a maximum U-value, an "Energy Rating" (ER) alternative and a maximum air leakage rate.
The U-value of the exterior wall is 0.166 W/([m.sup.2]*K) (thermal resistance, R = 34.1 h*[ft.sup.2]*F/BTU) and the roof has a U-value of 0.496 W/([m.sup.2]*K) (R = 11.5 h*[ft.sup.2]*F/BTU).