Smith County, MS Insulation Payback
Smith County, MS: what topping up your attic actually costs
DOE classifies Smith County as climate zone 3, hot-humid — summers that stay hot and humid while winters barely register on the energy bill. Its recommended attic R-value for bare joists is 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 2.8 years at an estimated $1,013/year saved. That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $725/year heating, $288/year cooling. Out of every 100 US counties tracked here, Smith County's savings potential beats roughly 18 of them. Within zone 3 specifically, it ranks 441st of 690 counties by estimated savings. Mississippi averages $1,022/year across the counties tracked here; Smith County comes in 1% lower.
Smith County's actual weather, not a national average
Smith County's climate figures — 2,733 heating and 1,808 cooling degree days a year — are read from RALEIGH 6N, MS US, 9.2 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Smith County sits at the 13th percentile nationally. Smith County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
Already have some insulation?
If Smith County's attic already has 3-4 inches of old insulation (about R-11) rather than bare joists, the recommended target drops to R-38. That smaller top-up costs around $1,620 and saves an estimated $136/year — payback about 11.9 years. This one is a genuine toss-up, not a clear yes.
Quotes and materials for this job
Get more than one quote before committing. Attic access and any needed air sealing move the price around, and most contractors won't take a job below roughly $600 regardless of size - worth asking upfront given Smith County's estimated $1,013/year on the line.
Nothing here is a guess
Every figure on this page traces to DOE/IECC climate zones and NOAA degree-day normals, documented in the methodology guide. The guide to what R-value actually means explains why R-49 is the target here specifically.