Recommended R-values in zone 1
These follow US Department of Energy and ENERGY STAR recommended levels for existing homes. Local building code may require more — check before you start.
Attic
R-49
Minimum R-30
Unlimited depth — the cheapest R-value in the house
Walls
R-13
Capped by framing depth
Floors over unconditioned space
R-13
Matters most over vented crawl spaces
Crawl-space walls
Not required
For sealed, conditioned crawl spaces
Where zone 1 is
States whose most populous area falls in zone 1:
Representative cities: Miami, FL · Key West, FL · Honolulu, HI.
Several states span three or more zones — California, Texas, Nevada, Arizona, Oregon, Washington, New York, New Mexico, and Idaho among them. Altitude matters as much as latitude. If you are near a boundary,check the map or confirm with your building department.
What insulating costs in zone 1
A 1,240 sq ft attic taken from bare joists to R-49 with blown cellulose, in this zone:
DIY total
$780–$1,400
Material, air sealing, blower, safety gear
Professional
$2,150–$4,250
Includes a 1.00× regional labor adjustment
Material needed
56 bags
14" of cellulose
Generated by the same engine as the calculator. Our assumptions.
What matters in this climate
- Radiant barriers are worth considering here, unlike most of the country
- Keep ductwork out of the attic if you possibly can — it is the hottest space in the house
- Ventilation and moisture control matter more than extra depth