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NOTES:
1. The term k refers to the amount of heat transferred through insulation 1-inch thick. It is Btu per hour, per square foot, per degree F temperature difference, per inch of thickness of insulation. Temperature difference is the difference between the temperature on one side of the insulation and that on the opposite side of the insulation.
2. The term C (conductance) refers to the amount of heat transferred through the total thickness of insulation. It is Btu per hour, per square foot, per degree F temperature difference, per specified thickness of the insulation.
3. The difference between k (conductivity) and C (Conductance) has to do with insulation thickness. C has the same value as k when the insulation is 1-inch thick.
4. R-values refer to the resistance to heat transfer, which is just the opposite of conductance. The R-value for 1 inch insulation is 1 divided by k. The R-value for total thickness is 1 divided by C. (R-values are commonly known as reciprocals of k and C and shown as 1/k and 1/C).
5. All values shown above are for a mean temperature of 200°F. This is the appropriate mean temperature for asphalt stored at 300°F. Please note that values of conductance (k and c) do vary significantly with mean temperature. Those values are smaller for lower mean temperatures and larger for higher temperatures. So, it is essential to know the correct mean temperature and use the same temperature for all comparisons. Moreover, since R-values are calculated as reciprocals of k and C, they too relate to a specific temperature. This means that R-values cannot be compared with each other unless all are based on values of k and C for the same temperature. Otherwise R-values are meaningless.
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