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 the Upstate. A steady share of that work is new-construction insulation for builders and general contractors: production homes in Greer and Simpsonville, custom builds in Clemson and Seneca, commercial projects in Spartanburg and Anderson.
This post is about how spray foam fits into a new build — what we spray and when, why it outperforms batts, and how the assembly holds up at inspection. If you frame houses for a living, this is the practical version.
New Construction Is When Foam Does Its Best Work
The build phase is the one time the entire envelope is open. Stud bays are empty, rafter and truss bays are fully accessible, and every wire, pipe, and duct run is still visible. Once drywall goes up, that access is gone for the life of the house — so what goes into the cavities now matters more than anything that comes later.
In the wall cavities we typically spray open-cell foam, which runs R-3.5 to R-4 per inch and fills the bay completely around wiring, plumbing, and blocking. Where the assembly calls for more R-value in less depth — rim and band joists, tight 2×4 walls, foundation walls on crawl-space plans — we switch to closed-cell, which runs R-6 to R-7 per inch and builds performance two or three inches at a time.
At the top of the house, we spray the underside of the roof deck itself rather than insulating the attic floor. That’s the unvented conditioned attic assembly, and it’s only practical to install while the rafter and truss bays are open — which is to say, during the build.
Why Spray Foam Beats Batts on a New Build
Fiberglass batts are the default bid on most new homes, and the problems are built in from the start. Batts sag in stud bays over time, leaving voids at the top of the wall. They get cut and stuffed around receptacle boxes, wiring, and plumbing runs, and every cut is a gap.
The bigger issue is air. Fiberglass doesn’t stop air movement at all — air washes through it and around it, so a wall can meet its R-value on paper and still leak at every penetration. Spray foam air-seals and insulates in one step: it expands into the bay, seals around everything that passes through it, and bonds to the framing. The insulation and the air barrier are the same pass, and foam doesn’t sag, settle, or drift.
Foaming the roof deck takes that further. The ducts and air handler end up inside the conditioned envelope instead of baking in a vented attic through a humid Upstate summer. For a builder, that means fewer comfort callbacks — bonus rooms and bedrooms over garages that actually match the thermostat.
How We Work Alongside Builders and GCs
Scheduling is where a subcontractor earns or loses the relationship, so here’s exactly where we land. We come in after rough-in inspections have passed — framing, plumbing, electrical, HVAC — and before your insulation inspection and drywall hang. The bays have to be open and rough-in complete before we spray, because once foam fills a cavity, nothing behind it is visible again.
One crew handles the whole envelope: walls, roof deck, rim joists, and the crawl space if the plan has one. You’re not coordinating a batt crew, a separate air-sealing sub, and a crawl space contractor against the same drywall date.
We coordinate directly with the superintendent, and when the schedule shifts — a failed rough-in, a late trade — we shift with it so the next trade isn’t standing around. We also perform insulation testing and evaluation as a standalone service, so if you need documentation of what went into the walls before they close, we can provide it.
Code Context: Climate Zone 3A in the Piedmont
The Upstate sits in IECC Climate Zone 3A — humid subtropical — in the Piedmont along the I-85 corridor. Inspectors across Greenville, Spartanburg, and Anderson counties check new homes against the Zone 3A envelope requirements: prescriptive R-values for walls and ceilings, plus air-sealing of the envelope.
A spray-foam assembly addresses both sides of that in one installation. The R-value comes from the foam’s per-inch performance, and because the foam itself is the air seal, most of the caulk-and-gasket punch list disappears with it. The unvented roof-deck assembly is a code-recognized approach, and it suits this climate — the attic and everything in it stay inside the conditioned space rather than exposed to outdoor air.
What New-Construction Foam Costs
Builders ask us for numbers early, and the honest answer is that we price per board foot — one square foot of coverage at one inch thick — so the total on any plan depends on the thickness applied and the area we cover. Open-cell runs $1.00 to $1.60 per board foot installed; closed-cell runs $1.60 to $2.60 per board foot installed. A 2×6 wall filled with open-cell is a different board-foot count than two inches of closed-cell, which is why we quote off the plan set or a site walk rather than over the phone.
Duke Energy serves most of the Upstate and runs rebate programs that change year to year, so confirm current amounts before you build them into a budget. And if your buyers ask about federal incentives: the 25C energy-efficiency tax credit expired December 31, 2025, and no federal insulation tax credit currently applies.