The number of respondents (48) does not result in a statistically significant survey but does serve as a good indicator that may reflect commonly held beliefs of other contractors. Almost 38 percent of those who responded to the informal poll did not use any form of load calculation, and others implied they were not using industry-recognized procedures. It is likely that many more HVAC contractors did not wish to reveal the fact that they are not performing standard load calculations.
There are many reasons for contractors not to do them: "The methods are too complicated for residential applications, I can't do it without a computer, I don't trust the results, the results don't match the equipment you can get, I don't have time, the rules of thumb work well enough, I can't take time to go to the classes, my customers say they aren't comfortable with a smaller system," etc.