1827sf Central Florida East Coast block one story on slab, lots & lots of single pane sliding glass doors and windows, open beamed family room, ducts sealed to within 6% total leakage, R30 added to attic, some windows tinted with 70% 3M film, average annual ACH of 0.40. Roof replaced in 2000 with Energy Star asphalt shinges (light grey).
I already had 3 different Manual J's, all recommending 3.5Ton based on combined sensible and latent cooling loads @ 0.75 SHR. I very much want to replace the old 1999 Rheem 3.5Ton with a 3Ton to save on electric, if it will keep me cool at design conditions. So when the last contractor came by on Monday to take measurements in preparation for his bid, I told him I really, really, would like the Manual J to prove to me that 3Ton is big enough. I shared with him the results of the blower door and infiltrometer testing and explained all I'd had done recently to improve the envelope, so his data would not be skewed towards a bigger unit. He even over-rated the shading on my glass doors in an attempt to "bump" the Man J a bit lower. I got the results awhile ago, and noticed he'd even lowered the size of my house by 100 square feet, maybe in error, maybe by design.
Regardless, this Man J also recommended 3.5Ton. Now I'm scared to undersize to 3Ton and skeptical about oversizing to 4Ton to take advantage of 2-stage. Since I'm "done" improving the envelope, I think I've pretty much got my mind made up to go with a single stage 3.5Ton. Leaning towards Broan equipment because parts are easy to get through RE Michel, but keeping an open mind.
Still need to find that "professional" installer who can convince me that he (or she) will do it right the first time. Someone who can use a manometer to take ESP and verify blower CFM against rated efficiency. Don't need someone looking to take my check to the bank hoping I won't notice the inefficiencies leading to higher than necessary electric bills until it's too late.