1. a wall is made up of four elements, as follows: ½” wood siding r = 0.81 ½” plywood sheathing r = 0.62 3½” fiberglass insulation r = 10.9 ½” sheetrock r = 0.45 (units of r-value are ft2-hr-of/btu) a. what is the total r-value of the wall? b. what is the r-value if no insulation is installed? c. in which direction (in or out) would the heat flow when the outside temperature is 90of and the temperature inside is 70of?