Heat Transfer Values
The American Society of Heating, Refrigerating, and Air — Conditioning Engineers (ASHRAE) has conducted considerable research into the thermal properties of building materials, and these data are used in the calculation of heat loss and heat gain. Tables of computed values for many construction materials and combinations of construction materials are made available through ASHRAE publications. One table gives the design values (i. e., conductivity values, conductance values, and resistance values) of various building and insulating materials. These values are used to calculate the coefficients of heat transmission (U-values) for different types of construction (e. g., masonry walls and frame partitions). Examples of these two tables have been taken from the 1960 ASHRAE Guide (see Tables 3-1 and 3-2).
The four heat transfer values contained in these tables are: (1) the k-value (thermal conductivity); (2) the C-value (thermal conductance); (3) the R-value (thermal resistance); and (4) the U-value (overall coefficient of heat transmission). Each of these heat transfer values will be examined before their use in heating and cooling calculations is explained.