I recently read an article by David Richardson from the National Comfort Institute where he said, “If you want to start a fight among HVAC contractors, ask them how to design a duct system. On one side of the discussion, you’ll have those who follow duct design rules of thumb that came from previous generations. Those “rules” probably came from their dad or someone else who taught them as they came up in the trade. To this group, disrespecting those rules is like spitting in the face of tradition and on the same level as insulting their mom…On the other side is the duct design die-hards who follow industry-approved standards.”