Help needed to calculate the R value of a brick veneer wall (house built in 1958)?
The only way to know the R-value of your wall is to know everything that was used to build it. Some of the ways you can determine this include by drilling a hole in it or looking behind an electrical outlet. That said, if your house is typical Canadian construction, here's my rough estimate:


1/2" drywall or plaster and lath: R-0.5
2x6 cavity filled with fiberglass batt insulation: R-14 (R-19 batts x 0.75 due to thermal bridging by the 2x6 studs).
Plywood sheathing: R-0.5
1" cavity: R-0.75
Single-wythe brick veneer: R-0.75


So the all-inclusive "whole-wall" R-value of your wall, if it's like this one, would be R-16.5. However, typically when discussing R-values, you only include the insulation--taking into account thermal bridging by studs. In that case, we would describe this wall as an R-14 wall. If your wall has different cavity insulation, or only has 2x4 studs, or has been retrofitted with rigid foam or mineral wool outside the sheathing, then the numbers would be different.