Just found out about this website load calc.net... Was wondering if anyone has used this or heard of it and if it is accurate
If it's this one; right click link & open in New TAB or New Window or it may not load!: http://www.loadcalc.net/ It is a whole lot better than guessing; it seems to compare close to my spreadsheet work on the same homes.
Use it to help you check equipment sizing - print the results as you can't save the calc you've done!
On a home that you will be optimally weatherizing, I’d use 0.4 ACH (Air Changes per Hour) be sure to add the (Air Changes per Hour) CFM into the ‘Fresh Air Recommended ‘line-slot, or it won’t figure the Infiltration & fresh air Btuh.
If your contractors don't do load calcs, suggest the free Whole House LoadCalc to them; they need to be doing them; plus the room by room calcs, that are just a little more work for checking on ductwork sizing!
A room needing 3,000-Btuh / by 30 is 100-CFM to that room, I'd probably use 105-CFM as there will be duct losses.
12,000 / 400-CFM airflow Per Ton of cooling is 30.
12000-Btuh / 450-CFM airflow per/ton is 26.6.
A 3000-Btuh room / 26.6 is 113-CFM to that room.