Quick duct design rules have been around for a long time and aren’t going anywhere in the near future. Multiple aspects of performance involving HVAC system components are being assumed with these rules. The effects these rules have on proper air delivery are often misunderstood.
The 0.10 friction rate is the most commonly used quick duct design friction rate for sizing ducts. The reason it is so widely used is that many slide duct calculators have a recommended residential setting on them of 0.10 inch of water column (wc). Just a word of advice, ignore this setting. If it is on the duct calculator you currently use, mark through it with a pen.