Time to replace my aging (18 years) AC systems in our 2 story house. Down stairs unit has stopped cooling completely and upstairs unit cannot keep up with demand, both are 2 1/2 ton Carrier units. I have received a couple of quotes and a Manual J was performed by one of the contracters, the other just eye balled everything and made recommendations.

My question is after reading so many posts on here, is it necessary to do a Blower Door test and Duct blaster in order to properly size the new units? None of the contactors I called, including some of the larger businesses here in Orlando, offer this service or think its necessary for proper sizing.