Zone 3A covers 637 counties in 12 states, home to about 46,704,373 people (FEMA NRI population). ENERGY STAR’s target for an uninsulated attic here is R49; with 3–4 inches already in place, add to R38.
Insulation targets for zone 3A
| Where | Guidance |
|---|
| Attic, uninsulated | R49 |
| Attic, 3–4 inches already | R38 |
| Floor over unheated space | R19 |
| Walls | When siding is removed: blow insulation into empty wall cavities, and add R5 insulative sheathing beneath new siding. |
| Basement or crawlspace walls | Add R5 insulative wall sheathing or an R13 batt. |
Homeowner retrofit guidance, not your local code. Your jurisdiction may enforce an older or amended IECC; ask the building department before a permit job.
What it means for upkeep
Most zone 3A counties fall in the mixed-humid Building America region. Real winters and humid summers: the house switches between heating and cooling twice a year, and freezes are short but real.
The “A” (moist) regime means humidity drives much of the care: drains, dehumidifying and keeping crawlspaces and basements dry.
See this month’s tasks for the mixed-humid region.
Largest counties in zone 3A
Wake County, NC1,128,357Mecklenburg County, NC1,114,693Fulton County, GA1,065,539Collin County, TX1,063,649Gwinnett County, GA956,460Shelby County, TN929,552Denton County, TX906,057Oklahoma County, OK795,336Cobb County, GA764,915DeKalb County, GA763,614Davidson County, TN715,485Jefferson County, AL673,766Tulsa County, OK668,481Guilford County, NC540,974Greenville County, SC525,347Virginia Beach City, VA458,853Richland County, SC415,644Charleston County, SC407,722Pulaski County, AR398,830Madison County, AL387,825Forsyth County, NC382,522Hamilton County, TN365,901Horry County, SC348,574Rutherford County, TN341,253Cumberland County, NC334,379Spartanburg County, SC327,446Durham County, NC324,580Clayton County, GA297,436Cleveland County, OK295,221Lexington County, SC293,888York County, SC281,543Cherokee County, GA266,412Forsyth County, GA251,239Chesapeake City, VA249,270Williamson County, TN247,523Henry County, GA240,522Norfolk City, VA237,884Union County, NC237,844Caddo Parish, LA237,695Smith County, TX233,253Berkeley County, SC229,449Montgomery County, AL228,847Gaston County, NC227,866Hinds County, MS227,510Tuscaloosa County, AL226,701Cabarrus County, NC225,772New Hanover County, NC225,344Shelby County, AL222,782Johnston County, NC215,586Muscogee County, GA206,469Richmond County, GA206,329Anderson County, SC203,620Onslow County, NC202,949Hall County, GA202,853Iredell County, NC186,589Newport News City, VA186,209DeSoto County, MS185,280Lee County, AL173,871Alamance County, NC171,316Pitt County, NC169,746 States in this zone: Georgia (118), North Carolina (79), Mississippi (76), Arkansas (63), Oklahoma (59), Texas (58), Alabama (58), South Carolina (44), Tennessee (34), Louisiana (27), Virginia (19), Missouri (2).