R- Value: Thermal Resistance
The measure of the ability of
a material to resist heat flow.
The higher the "R" Value the greater
the thermal efficiency.
V-Value: Overall Heat Transmission
Coefficient
A unit used to express heat passage
through a complete building section, including air films. U-Values
serve as a basis for determining transmitted heat loss. The lower the
U-Value, the higher the insulation value.
K- Value: Thermal Conductivity
A unit used to express the amount of
heat, in BTU's per hour, that passes through one square foot of
homogeneous material that is exactly one inch thick and has a
temperature difference of one degree Fahrenheit between its surfaces. As
the KValue decreases, so does the amount of heat permitted to pass
through the material.
C- Value: Thermal Conductance
A measure of the amount of heat
passing through materials of any thickness.
Calculated Thermal Values
The reciprocal of the calculated
U-Value. By definition it is the summation of all the R-Values for
each of the building's components. This method of calculation does not
consider the thermal short circuit effect of structural members,
fastener population or the compression of the insulation at its
structural members. It should also be noted that this type of
calculation often indicates heat loss values for building envelopes
that are lower than those actually found in the finished structure.
F: Surface Air Film Coefficient
The amount of heat flow in BTU per
square foot per hour between an exposed surface of a material and the
adjacent air. It is the measure of the conductance of heat through the
air film that clings to all surfaces.
