Start from the Zone 2 R-value target. ENERGY STAR recommends R49 for an uninsulated attic floor in Climate Zone 2, and R38 if there are already 3 to 4 inches of insulation up there. Open-cell foam delivers roughly R-3.6 to R-3.8 per inch, so R49 takes about 13 to 14 inches. Closed-cell delivers about R-6.5 per inch, which puts the same target near 7 to 8 inches. Before you compare two bids, find out which R-value each one is priced to. A cheaper number almost always means thinner foam, and an inch shaved off a closed-cell roof deck is roughly R-6.5 of performance you paid for and did not get.
Humidity is why closed-cell keeps winning here. A U.S. Department of Energy Building America project in Louisiana used closed-cell spray foam in the attic, walls, and under floor specifically to build moisture- and flood-resistant homes. Closed-cell acts as an air barrier and a vapor retarder in one pass, which is what stops humid outside air from reaching a cool surface inside your wall or roof assembly and condensing there. That is the whole ballgame in Southwest Louisiana. Open-cell spray foam still earns its place on interior walls, for sound control, and on budget attic jobs where drainage and roof condition are solid, but on a Sulphur roof deck closed-cell is the default recommendation for a reason.
Your permit runs through Calcasieu Parish. The parish enforces the current code editions adopted by the Louisiana State Uniform Construction Code Council, including the International Residential Code and the International Energy Conservation Code, with the LSUCC 2023 amendments in effect since January 1, 2023. Ask who is pulling the permit before anyone mixes a drum. An installer who tells you a foam job never needs to be on record is telling you something about how they work.
If your ducts are in the attic, foam the roof deck. Most Sulphur homes built before the last decade have the air handler and ductwork sitting in a vented attic that hits 130 degrees on a July afternoon. Spraying the underside of the roof deck brings that whole volume inside the thermal envelope, so the ducts are no longer leaking cooled air into an oven. Attic spray foam done this way is an unvented assembly, which means the existing soffit and ridge vents get sealed and the job has to be detailed correctly. It is not a job to hand to a crew that has done three of them. Done right, it is the single change that moves a summer electric bill in this parish more than anything else short of replacing the system itself.
Raised floors and crawl spaces are the other Sulphur-specific job. Plenty of homes here sit on piers, and an open crawl space in this climate pulls ground moisture straight into the subfloor. Symptoms show up as cupping floors, a musty smell that never clears, and an HVAC system that runs long without ever feeling dry. Crawl space encapsulation plus closed-cell foam on the rim joists shuts that path down. Budget $1,500 to $3,200 for a typical 1,000 square foot crawl.
Metal buildings need foam, not batts. Shops, warehouses, and pole barns along the industrial corridor sweat on the inside of the steel every time a humid morning meets a cooled interior. Fiberglass hung against metal absorbs that condensate and sags within a couple of seasons. Closed-cell foam sprayed directly to the panel stops condensation at the surface because there is no gap for moist air to reach. Commercial spray foam on a metal building typically runs $4,000 to $14,000 or more depending on square footage and wall height.
Rebuilds and new builds get the cheapest version of this job. If you are still working through storm repairs, foam goes in easiest while the wall cavities are already open, and a retrofit at that stage costs a fraction of tearing finished walls back down later. On a new build, new construction spray foam is scheduled at rough-in after mechanicals and before drywall, so getting the installer on the calendar early matters more than the price per board foot.
What to do next. Get a written quote that shows square footage, foam type, target thickness, and total board feet, then price it against the ranges below. Our Sulphur, LA service page covers what local jobs look like and how scheduling works, and you can request a written quote with your square footage and the problem you are trying to solve. Ballpark numbers over the phone are fine for planning. Nobody should sign one.