Dorchester County, SC Insulation Payback
Dorchester County attic insulation, by the numbers
Dorchester County sits in IECC climate zone 3 (Hot-Humid) — humid heat for much of the year, with cooling running far more than heating ever does. For a currently uninsulated attic, DOE and ENERGY STAR recommend building up to R-49. Going from R-2 to the recommended R-49 costs roughly $2,820 installed for a typical attic (about 1,000 sq ft), and pays for itself in about 3 years at an estimated $950/year saved. Topping up the attic pays for itself fast here.
The breakdown behind the number
Split it out and it's roughly $633 a year on the heating side, $317 on cooling. By estimated insulation savings, Dorchester County lands in the 13th percentile nationally. Zone 3 alone covers 690 counties in this dataset, and Dorchester County comes in 574th by savings. South Carolina averages $1,016/year across the counties tracked here; Dorchester County comes in 6% lower.
The climate data behind this
Dorchester County's climate figures — 2,385 heating and 1,988 cooling degree days a year — are read from SUMMERVILLE 4W, SC US, 10.5 miles away, NOAA's nearest 1991-2020 normals station. Combined heating and cooling load puts Dorchester County in the 8th percentile of this 3,162-county dataset. One local detail the R-value alone won't tell you: Dorchester County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
If the attic isn't bare
Already have a few inches up there? Topping R-11 up to R-38 runs about $1,620 for about $128/year saved — roughly 12.7 years to break even. Call this borderline rather than a clear win.
Getting it done in Dorchester County
Actual quotes will vary by attic access, existing debris, and whether the job needs air sealing first. Treat the $2,820 figure above as a planning number for Dorchester County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Where these figures come from
Dorchester County's R-49 target and its degree-day figures both come from named federal sources - see the methodology guide for exactly which ones. The guide to what R-value actually means explains why R-49 is the target here specifically.