U-value notion

[takayori]

Hi guys,

How do you describe "U-value" in general terms?

Can I say "the energy that will flow in 1 second through 1 square meter of the material with a temperature differential of 1°C. "?

 

[bimr]

Thermal transmittance, incorporates the thermal conductance of a structure along with heat transfer due to convection and radiation. It is measured in the same units as thermal conductance and is sometimes known as the composite thermal conductance. The term U-value is another synonym.

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

 

[SlideRuleEra]

...also, the "R-value" which is commonly used to rate various insulating materials is actually the reciprocal of the "U-value".

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[concretemasonry]

The "U" or the reciprocal ("R" value) is a measure of the heat loss of a material through conductance.

For a wall or section there are calculation methods for specific configurations and radiant and convective loss can be added in accordance with recognized methods.

Be very careful with any calculated parallel heat flow loss can be very erroneous and unrealistic compared to tested wall sections. If there is a combination of materials with widely varying conductance (steel and insulation as an example), the series-parallel method gives far better agreement with actual tests. Because of the time and cost of actual wall or detail sections, calculations are frequently used to provide an estimate of the actual heat loss.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.