Want to add another A/C duct to existing system.

Hi guys. I have 7 round alu flexible ducts coming from my rectangular galv main works in the basement that serve the entire house with A/C and heat. One duct serves only the upstairs bathroom and goes up the wall between joists on what was an exterior wall but is now an interior wall in my new Florida room. I know everything is possible with enough money and engineering expertise, but how easily can I open the wall where the duct goes up and tap in to it for A/C and heat in the Florida room (12' x 14') and put a simple vent in the wall? And will it effect the entire system very much? Look forward to your advice. Cheers and best regards, Rughead.

That's a big room, and probably with lots of windows to use one duct to service it. And, the bathroom would likely not cool as well. With the added floorspace, you should probably redo the manual-j (heat loss cal) for your house and see first, if the thing can handle the additional load. Sometimes, yes, sometimes no. The only good thing about adding more load is that the thing will run longer, and if it wasn't already, it will pull more moisture out of the air, but may no longer reach the desired temp. You'd probably be better to tap off the main with a new run, than tapping off the existing single run to branch into that room.

Thanks Jim. I'll look closely at the main to see if I can make a new run. It's only a few feet. Cheers and best regards, Rug.