We’re South Carolina Spray Foam Insulation, a family-owned insulation company with more than 15 years of residential and commercial work across Greenville and the rest of Upstate South Carolina. The attic insulation Greenville SC homeowners call us about usually comes down to the same problem: the attic is outside the home’s thermal envelope, but the ductwork, air handler, wiring, and ceiling penetrations are all sitting inside it.
Greenville sits in IECC Climate Zone 3A, a humid subtropical zone where summer heat gain and moisture move together. In the Piedmont, up against the Blue Ridge foothills, roof decks take a hard afternoon load from late spring through early fall. Homes along the I-85 corridor through Greenville, Greer, Spartanburg, Anderson, Mauldin, Taylors, Easley, Simpsonville, Clemson, Seneca, and Rock Hill often have vented attics with fiberglass or blown insulation on the attic floor. That setup can work on paper, but only when the ceiling plane is perfectly air-sealed and the ductwork is not losing energy in the hottest part of the house.
Our attic work is built around spray foam insulation and air sealing. In most Upstate roof-deck applications, we install open-cell spray foam to create an unvented, conditioned attic assembly. Closed-cell spray foam has its place when thickness is limited or moisture resistance is the deciding factor, but open-cell is the common attic specification because it fills irregular framing, seals air movement, and costs less per board foot.
Why Upstate Attics Run So Hot
An attic under dark shingles can run far above the living space on a July afternoon. That radiant heat does not stay politely above the ceiling. It heats the ductwork, the air handler, the ceiling drywall, and every small gap around can lights, bath fans, plumbing chases, and top plates.
When the attic floor has batts or loose-fill insulation, the insulation is only protecting the ceiling plane. The attic above it remains a hot, vented buffer zone. If ducts run through that space, your HVAC system has to push conditioned air through an environment it was never meant to fight.
We see this across Greenville and Spartanburg homes built with traditional vented attics: upstairs rooms that never settle, supply air that warms before it reaches the register, and air conditioners that cycle longer even after the thermostat is set correctly. The insulation is not always missing. Often it is simply the wrong assembly for the way the house is built.
Roof-Deck Foam vs. Batts on the Attic Floor
Fiberglass batts and blown insulation can provide R-value when they are dry, evenly installed, and protected from moving air. Most older Upstate attics fail at least one of those conditions. Gaps around framing, compressed batts, wind-washed eaves, and unsealed penetrations all lower the real performance below the label.
Spray foam changes the control layer. Instead of insulating only the attic floor, we apply foam to the underside of the roof deck and seal the attic into the home’s thermal envelope. Open-cell spray foam runs roughly R-3.5 to R-4 per inch and expands into the seams, corners, and roofline changes that batts cannot fill. Closed-cell spray foam runs roughly R-6 to R-7 per inch and adds a denser air and vapor-resistant layer where the assembly calls for it.
That matters because air leakage is as much of a problem as R-value. A leaky attic floor lets conditioned air escape upward and pulls humid outdoor air into the house to replace it. Foam and air sealing address both sides of that loss.
Unvented, Conditioned Attic Assemblies
An unvented attic is not just a vented attic with foam sprayed in it. The roof deck, gable ends, penetrations, and transition points have to be sealed as one continuous assembly. Once that is done correctly, the attic becomes a semi-conditioned space instead of an outdoor chamber above the ceiling.
That is the reason roof-deck foam is so useful in Upstate homes with ductwork in the attic. Ducts and air handlers work better when they are inside a tempered space. They lose less heat in winter, gain less heat in summer, and are less exposed to humid air that can condense on cold surfaces.
We evaluate the roof, ventilation layout, existing insulation, and access before recommending the assembly. Some projects call for removing old attic-floor insulation so the house can dry and perform as one system. Some new-construction insulation projects start clean, which gives us more control over the air barrier from the beginning.
What We Install
We install open-cell and closed-cell spray foam, air sealing, vapor and moisture barrier work, crawl space insulation, new-construction insulation, and insulation testing and evaluation. For attics, the usual scope is open-cell foam at the roof deck plus targeted air sealing where the roofline, framing, and mechanical penetrations need it.
Closed-cell foam may be the better fit in tight spaces, transition areas, or assemblies where added vapor resistance matters. We do not quote that from a distance. We inspect the attic first, look at the roof deck, framing depth, access, and mechanical layout, then recommend the foam type and thickness that fit the building.
Attic Spray Foam Cost in Greenville and the Upstate
Spray foam pricing is measured per board foot: one square foot at one inch thick. Open-cell spray foam runs $1.00 to $1.60 per board foot installed. Closed-cell spray foam runs $1.60 to $2.60 per board foot installed. Thickness changes the math, so a five-inch open-cell application is priced very differently from a one-inch pass, even over the same square footage.
Access, roof pitch, attic height, old insulation removal, and how much air sealing is needed all affect the final quote. That is why we price attic insulation after an on-site insulation evaluation, not from a total project figure guessed over the phone.
Duke Energy serves much of the Upstate and may offer rebates for qualifying insulation and air-sealing work. Those programs change annually and the amounts vary, so confirm current amounts before planning your project. The federal 25C energy-efficiency tax credit expired December 31, 2025, so we do not present it as an active insulation credit.
Attic Spray Foam Insulation in Greenville, SC: Should You Seal the Roof Deck?
We're South Carolina Spray Foam Insulation, a family-owned company that's spent more than 15 years insulating homes and commercial buildings across Greenville and the rest of Upstate South Carolina. When homeowners ask us about attic insulation, the real question underneath is usually this one: leave the fiberglass batts on the attic floor, or seal the roof deck with spray foam? In Climate Zone 3A, with ductwork overhead and months of radiant heat coming through the shingles, our answer is usually the roof deck. Here's the reasoning.
The traditional assembly puts fiberglass batts between the ceiling joists and vents the attic above them, on the theory that outdoor air will flush the heat out. The batts are asked to separate your living space from the hottest part of the house — and in a Piedmont summer, that attic is brutal. From late spring through early fall, the sun drives roof surface temperatures well past the outdoor air temperature, and the deck radiates that heat down onto everything below it.
When we spray foam to the underside of the roof deck, the thermal and air boundary moves from the ceiling plane up to the roofline. The attic becomes an unvented, conditioned space — inside the envelope of the home rather than outside it. The soffit and ridge vents get sealed off, because the assembly no longer depends on outdoor air flushing the attic.
Seal the roof deck and the ducts end up in semi-conditioned space, so cooled air arrives at the register close to the temperature it left the air handler. For a lot of the homes we evaluate in Greenville, Greer, Mauldin, and Simpsonville, the ductwork argument alone justifies the assembly — the comfort improvement on the second floor is that direct.
The product we install most often at roof decks is open-cell spray foam. It delivers roughly R-3.5 to R-4 per inch, so a typical application of five to six inches at the roofline gets the assembly where it needs to be, and it expands into the rafter bays and around every nail and penetration for a continuous air seal. It's also the lower-cost option per board foot.
We'll be honest about the exception. If the attic holds no ducts and no air handler, the ceiling plane is tight, and the existing batts are deep and dry, the roof-deck case gets weaker. That combination is rare in the houses we see from Easley to Clemson — most Upstate construction puts the HVAC overhead — but when we find it, we say so. In those cases, air sealing the ceiling plane is sometimes the higher-value first step, and it's work we perform as a standalone service.
