We’re South Carolina Spray Foam Insulation, a family-owned company, and we’ve spent more than 15 years insulating homes and commercial buildings across Greenville and the rest of Upstate South Carolina. The spray foam insulation Greenville property owners call us about usually starts with the same handful of complaints: rooms that won’t hold temperature, energy bills that climb every summer, or a crawl space that’s been damp since the day the house was built. In our experience, the insulation itself is usually part of the problem — and the right foam, installed in the right places, is how we fix it.
Greenville sits in IECC Climate Zone 3A — humid subtropical — in the Piedmont, up against the Blue Ridge foothills. From late spring through early fall our air carries real moisture, and the red-clay soil under most of the Upstate doesn’t dry out quickly; it releases dampness steadily toward anything built above it. Most homes along the I-85 corridor through Anderson, Greenville, Greer, and Spartanburg — and plenty more in Easley, Mauldin, Taylors, Simpsonville, Clemson, Seneca, and Rock Hill — were insulated with fiberglass batts and left to breathe through gaps and vents. That assembly was never designed for this humidity. Spray polyurethane foam insulates and air-seals in a single pass, which is why we install it every week in crawl spaces, attics, walls, and rim joists across the Upstate.
The Two Foams We Install: Open-Cell and Closed-Cell
Open-cell foam expands to many times its liquid volume and cures soft and flexible, at roughly R-3.5 to R-4 per inch. It’s vapor-permeable, which makes it the right product for attic roof decks and interior applications where you want assemblies that can dry — and it’s the lower-cost option per board foot.
Closed-cell foam is dense, rigid, and delivers roughly R-6 to R-7 per inch. At two inches or more it acts as its own vapor retarder, so it’s what we spray on crawl space foundation walls, rim joists, and any surface with direct moisture exposure. It bonds hard to block and poured concrete, closing the mortar gaps and voids we find in older Upstate foundations.
Plenty of projects use both — closed-cell below, where the moisture lives, open-cell above, where budget and drying potential drive the decision. The two products aren’t interchangeable, and part of every insulation evaluation we perform is walking the property and deciding which foam goes where.
Where We Install Spray Foam in Upstate Homes
Crawl spaces. This is where Zone 3A humidity concentrates. We air-seal the foundation vents and the obvious gaps, spray two to three inches of closed-cell foam on the foundation walls and across the rim joists, and finish the ground plane with a heavy-duty vapor barrier, overlapped and sealed at the piers and walls. Crawl space insulation done this way cuts the space off from outdoor humidity instead of trying to fight it with fiberglass under the floor.
Attics. An unconditioned Upstate attic in July is brutal on anything inside it — especially ductwork. Open-cell foam on the underside of the roof deck pulls the attic inside the conditioned envelope, so ducts and air handlers stop losing capacity to the temperature differential.
Rim joists. The perimeter framing where the floor system meets the foundation wall is typically the leakiest strip in the house. Two inches of closed-cell here seals a major infiltration pathway in one visit.
New construction and commercial work. Builders across Greenville, Spartanburg, and Anderson call us for new-construction insulation — wall cavities, roof decks, and crawl spaces — and we serve commercial clients as well as residential.
Why Foam Outperforms the Alternatives in This Climate
Fiberglass batts resist conducted heat at their rated R-value in lab conditions, but they don’t air-seal. Every gap around a pipe penetration, every batt that’s sagged away from the subfloor, is an open path for humid Upstate air — and fiberglass loses effective R-value as it absorbs moisture, which happens reliably in Zone 3A crawl spaces and attics.
Blown-in products on an attic floor are inexpensive and do what they do, but the ducts above them are still sitting in unconditioned space, and every unsealed top plate and recessed light undercuts the assembly. Rigid foam board has its uses, but it doesn’t conform to irregular framing and leaves gaps at penetrations. Spray foam fills those gaps as part of the installation — the air sealing and the insulation happen in the same step.
What Spray Foam Insulation Costs in Greenville
Spray foam is priced per board foot — one square foot of coverage at one inch thick — so the honest answer on cost always depends on the thickness applied and the square footage we cover. Open-cell runs $1.00 to $1.60 per board foot installed; closed-cell, the product we recommend on foundation walls and rim joists, runs $1.60 to $2.60 per board foot installed. Two inches of closed-cell costs roughly double the single-inch rate before any prep or old-batt removal. Access, wall height, and existing conditions all move the number, which is why we quote only after an on-site insulation evaluation — never sight unseen.
Duke Energy serves most of the Upstate and offers rebates for qualifying insulation and air-sealing work. The amounts vary by measure and change annually, so confirm current amounts before you schedule — we’ll point you toward the right program during your estimate. As for federal incentives: the 25C energy-efficiency tax credit expired December 31, 2025, and no federal insulation tax credit currently applies. Any contractor still advertising one is working from outdated information.
