Long winded question I need advice on.
I just purchased a 3/2 home in miami, fl with a 1 car garage. The house is currently under 1324 SF of air conditioned space. The house is a cookie cutter model built in 1988 with the original 2.5 ton split system a/c. The house needs a new a/c before I move in and I will be going with a 14 SEER model.
I will be adding an extra bedroom inside the garage which will increase the area under a/c to 1468 square feet.
I performed the calculations in Manual J to figure out what size a/c I will need for the house with the additional room. As of right now, my figures tell me that I need a 3.34 ton system.
The advice that I need is this. If I were to install an a/c based on 3.34 tons, would I go with a 3.5 ton system? I also plan on building a covered patio on the back of the house where most of the large sliding glass doors are. Once these sliding glass doors get shaded from the patio roof structure, Manual J reduces my a/c requirement to 2.93 tons. Should I get the 3 ton in anticipation of the patio or the 3.5 ton?
What would happen if I went with the 3.5 ton and a year from now, the patio gets built shading the windows? What negative impacts should I anticipate?
Thanks in advance for any advice.