# thermal conductivity

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## thermal conductivity

n.
A measure of the ability of a material to allow the flow of heat from its warmer surface through the material to its colder surface, determined as the heat energy transferred per unit of time and per unit of surface area divided by the temperature gradient, which is the temperature difference divided by the distance between the two surfaces (the thickness of the material), expressed in watts per kelvin per meter.

## thermal conductivity

n
(General Physics) a measure of the ability of a substance to conduct heat, determined by the rate of heat flow normally through an area in the substance divided by the area and by minus the component of the temperature gradient in the direction of flow: measured in watts per metre per kelvin. Symbol: λ or k Sometimes shortened to: conductivity
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in periodicals archive ?
To make sure they make the most educated decision, homeowners can investigate the solar heat gain coefficient, U-factor, visible transmittance and light-to-solar gain.
[??] = A[DELTA]T/[[R.sub.inside] + [R.sub.insulation] + [R.sub.outside]] [??] = [(10 /t)(12 /t)(72[degrees]F-63[degrees]F)]/[0.5 [[ft.sup.2] hr[degrees]F/BTU] + 7[ft.sup.2] hr[degrees]F/BTU] + 0.5[ft.sup.2] hr[degrees]F/BTU] = 135[BTU/hr] Table 5: 2018 National Engineering Computation Challenge (Sample Question #4--correct solution underlined) Question: How does doubling the area of the glass in the window and frame affect the U-factor of the assembly?
U-Factor measures the rate of heat flow through the window.
U-factor for above grade assemblies was calculated following the "New Construction Guide" from New Buildings Institute (NBI 2015).
This allows It to achieve a U-factor of 0.58 BTU/hour-square foot-degree F., nearly half the thermal conductivity of a typical single pane window at 1.025 BTU.
Also, the windows selected were high performance, having a total unit performance U-factor of 0.17 and a solar heat gain coefficient (SHGC) of 0.24 with visible light transmittance of 43% for fixed glazing, and U-factor of 0.21 and a SHGC of 0.21 with visible light transmittance of 37% for operable awning windows.
Which of the following statements about U-factor and R-value are true?
The glass is a high performance Softcoat Low Emissivity (Low E) glass to achieve a lower U-factor (heat loss/gain) or Solar Heat Gain Coefficient (SHGC) The glass is sprayed with a coating of metal oxide particles that produce a higher heat reflectance.
To develop methods to compute light transmittance and solar heat gain coefficient (SHGC) at all relevant sun altitude angles, and thermal transmittance (U-factor) under given environmental conditions in commercial and residential buildings;
* Alpen High Performance products 9H and L series windows, averaging U-factor of 0.15.
Think about U-factor as the opposite of insulation R-values where the higher the R-value, the better the insulation.

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