Johnson County, TX Insulation Payback
Johnson County, TX: what topping up your attic actually costs
Johnson County, Texas is zone 3 under DOE's climate map (Hot-Humid), which means humid heat for much of the year, with cooling running far more than heating ever does. An uninsulated attic there should be built up to R-49. For an attic around 1,000 square feet, closing the gap from R-2 to R-49 costs around $2,820 and saves an estimated $1,044 a year — payback in roughly 2.7 years. That's about as fast as attic paybacks get.
Heating vs. cooling in Johnson County
The estimated savings split roughly $648/year heating, $396/year cooling. Out of every 100 US counties tracked here, Johnson County's savings potential beats roughly 20 of them. Within zone 3 specifically, it ranks 373rd of 690 counties by estimated savings. Texas averages $1,035/year across the counties tracked here; Johnson County comes in 1% higher.
Johnson County's actual weather, not a national average
The heating and cooling degree days behind this estimate — 2,442 HDD and 2,484 CDD (base 65°F, 1991-2020 normals) — come from CLEBURNE, TX US, the nearest NOAA station with published normals, 5.1 miles from Johnson County's center. Combined heating and cooling load puts Johnson County in the 24th percentile of this 3,162-county dataset. Johnson County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
The smaller top-up scenario
If Johnson 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 $141/year — payback about 11.5 years. This one is a genuine toss-up, not a clear yes.
Quotes and materials for this job
Real bids depend on how easy the attic is to reach and whether old insulation needs removing first, so treat $2,820 as a starting estimate for a Johnson County job, not a quote. Expect at least a $600 minimum charge from most contractors.
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.