Currently, we have 14" main flex duct and 8" flex duct for outlets. Measurements were taken from outside sides so probably the inside airflow diameters are little smaller. We are doing an addition and the ac contractor said that we need a 4 ton after doing computer calculations. He also said that the existing duct is not big enough. We are on a tight budget.
Is the existing duct enough for a 4 ton ac?