Long Read, but I’m trying to paint a picture for the think tank here.

Has anybody ever used something like a Fiberglass Acoustic Board (Certainteed AcoustaBoard Black R in this case) for a continuous exterior insulation underneat a rainscreen set up?

I’m in the planning / material acquisition process for the reconstruction of my 1934 home, Zone 2 (Central FL), and I’m looking to do this as low cost as possible (i.e. doing all work myself, no loans, renovating as cash flow from my day job comes in).  There’s a lot of construction projects going on in this area, so there is a decent selection of surplus building materials available for a fraction of Retail pricing.  I Plan on retiring in this house, so I’m looking to get best ROI to live without a mortgage and keep future costs as low as possible.  I also am well aware of the Good/Fast/Cheap equation, and I’m okay with eliminating the Fast option.

I have an opportunity to pick up enough 4×8 Certainteed AcoustaBoard Black R 4.3, https://www.certainteed.com/products/technical-insulation-products/acoustaboard-black-toughgard-facing) sheets for my project, and to soundproof interior walls between rooms, at an incredibly low cost (like 15-20 bucks a sheet, leftover from a commercial project.)

Pertinent Details: ~1000 sf Pier and Beam Wood Frame Construction, which will pretty much be rebuilt to meet FBC 2023 Codes, due to 90 years of Termite damage thoroughout on a completely open crawl space – no walls (plan on using a foil faced insulation underneath floor joists at R-5, taped at all seams, with joist cavities insulated with mineral wool to prevent critters from getting too comfortable;   (2×4 walls planned, thinking Mineral Wool in Stud Cavities, Regular OSB Sheathing, with Prosoco R-Guard Cat5 Rain Screen or R-Guard Spray Wrap Rain Screen liquid applied WRB/Air Barrier + R-Guard Liquid Flashing System, Continuous Exterior Insulation, PT 1×4 Rain Screening, and either Hardy or LP Smartside lap siding.

Questions that are keeping me up at night as I plan the project in my head, below:

—-Am I asking for trouble by using a Fiberglass Board for Continuous Exterior insulation? I’m trying to get my head around vapor transmission rates, but this stuff looks like unfaced (no aluminum or kraft paper, etc) duct board.  It’s fiberglass bonded with a thermoset resin, so I don’t think there’s any mold / rot issue being up against the liquid WRB with a 10-15 Perm Vapor Rating

—Is even pursuing Continuous Exterior Insulation / Thermal Bridging Prevention juice even worth the monetary squeeze where our coldest winter conditions are measured in hours rather than days consisting of mid 30’s-40’s at night.  I’m on the coast (3-4 miles inland from ocean), and we get into upper 90’s on the hottest summer days. Mean Annual Temperature is 75 degrees F, and we get about 45 inches of rain per year.

     I understand air sealing is pretty important, and I’m pretty concerned about moisture rot, which attracts termites, etc.  Lots of PT lumber being used throughout this build, termite shields, soil treatment around piers and any ground contact areas, followed up with a Borate Treatment of all wood (belt and suspenders) prior to closeup of walls.  You can probably get that I hate termites at this point.

Thanks!