SPEER, South-central Partnership for Energy Efficiency as a Resource (SPEER) provided a great HVAC video explaining size and ducts today, webinar. The video is now on their you tube channel, https://www.youtube.com/watch?v=YmBvkn-3SGs&t=1372s. The explanations were geared to those of us that are not Professional Mechanical Engineers. Each region of the USA has their own group like SPEER. They are a great Energy inspection resource. You also get 1 hour ICC credit for each webinar. Hope this helps ya’ll.
Thanks for posting, James. Very Informative