waterproof wall panels for coastal house
I have a coastal house and am finishing out a ground-level room that may be subject to as much as 8 feet of water depth during a severe hurricane. I have used pressure treated 2x8 studs, treated 5/8 sheating, and red cedar shakes for the structure and exterior finish. For the interior finish I want it to be a high-quality, finished look like the rest of the rooms in the upstairs floors, but I do not want flood waters to result in damage and repair costs. I do not want to use any gypsum or tile backer product (drywall, denshield, durock, hardy backer, etc.) because the manufacturers say they will not handle the immersion without structural failure, paint peeling, etc. So I am just about ready to use Ipe' hardwood decking material as wall paneling. I plan to drill drain and vent holes in the paneling at the bottom and top of each stud cavity, along with vent holes in each stud to promote cross-talk ventilation and to try to stop mold and mildew growth. I do not plan to insulate the stud cavities since I am not aware of any material that would take the water and not promote mold and mildew.
Before proceeding with my Ipe' plans, I wanted to check with boat builders and boards like yours to make sure there's not a better, less expensive, and less time consuming way to do this. The Ipe will cost me about $3 per sqaure foot (1000 square foot wall and ceiling coverage) plus a ton of time drilling and screwing with stainless deck screws. Could I use some form of waterproof plywood or composite panels, whose joints could be finished with waterproof materials, smoothed down to hide the joints, then painted?
Thanks in advance for any help.