Sussex County, DE Insulation Payback
Attic insulation payback for Sussex County, DE
DOE classifies Sussex County as climate zone 4, mixed-humid — a genuine mix of cold winters and humid summers, with neither one dominating the bill. Its recommended attic R-value for bare joists is R-60. Topping up a typical 1,000-square-foot attic from bare joists (R-2) to R-60 runs an estimated $3,480, and saves about $1,312 a year in heating and cooling — a payback around 2.7 years. Hard to find a home improvement with a faster payback than this.
Where the savings come from
Of that, about $1,088/year comes from reduced heating and $224/year from reduced cooling load through the ceiling. Sussex County beats 39% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 825 counties DOE places in zone 4, Sussex County ranks 559th. Against Delaware's own average of $1,363/year, Sussex County runs 4% below that.
Where these numbers come from
Sussex County's climate figures — 4,070 heating and 1,396 cooling degree days a year — are read from GEORGETOWN SUSSEX CO AP, DE US, 1.6 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Sussex County sits at the 39th percentile nationally. DOE also classifies Sussex County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
The smaller top-up scenario
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $191/year saved — roughly 11.9 years to break even. It is close - the payback only just fits a reasonable timeframe.
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 Sussex County's estimated $1,312/year on the line.
More on how this was built
Nothing here is a guess: the methodology guide names the DOE climate map and NOAA station data behind every number on this page. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.