Portsmouth city, VA Insulation Payback
Portsmouth city, VA: what topping up your attic actually costs
Portsmouth city, Virginia is zone 4 under DOE's climate map (Mixed-Humid), which means heating load in winter and cooling load in summer, both worth taking seriously here. An uninsulated attic there should be built up to R-60. For an attic around 1,000 square feet, closing the gap from R-2 to R-60 costs around $3,480 and saves an estimated $1,161 a year — payback in roughly 3 years. That's about as fast as attic paybacks get.
The breakdown behind the number
The estimated savings split roughly $903/year heating, $258/year cooling. Out of every 100 US counties tracked here, Portsmouth city's savings potential beats roughly 29 of them. Within zone 4 specifically, it ranks 783rd of 825 counties by estimated savings. Virginia averages $1,342/year across the counties tracked here; Portsmouth city comes in 13% lower.
Where these numbers come from
The heating and cooling degree days behind this estimate — 3,378 HDD and 1,608 CDD (base 65°F, 1991-2020 normals) — come from NORFOLK S, VA US, the nearest NOAA station with published normals, 7.1 miles from Portsmouth city's center. That combined heating-and-cooling load ranks Portsmouth city 2364th nationally by total degree days — the 25th percentile. Portsmouth city 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 Portsmouth city's attic already has 3-4 inches of old insulation (about R-11) rather than bare joists, the recommended target drops to R-49. That smaller top-up costs around $2,280 and saves an estimated $169/year — payback about 13.5 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 Portsmouth city's estimated $1,161/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-60 is the target here specifically.