Northeast: energy calcs & Manual J.
The Jacksonville station’s 94°F and 32°F, outside Duval.
Clay, Nassau and Baker counties all take Jacksonville Cecil Field's design limits, 94°F cooling and 32°F heating, the hottest summer and one of the coldest winters in Florida's design data. Putnam uses Gainesville's 92°F and 33°F. All four are climate zone 2A, so heat-pump sizing needs a real heating check.
- Counties
- 4 countiesClay, Nassau, Baker and Putnam
- Departments
- Each county’s ownSeveral cities run their own · what we publish
- Code edition
- FBC Energy Conservation, 8th Ed. (2023)9th Ed. (2026) scheduled for Dec 31, 2026 · what changes
- Price
- $195 · $445 · $595Energy calc from · full package · sealed. Same in all 67 counties · price list
- Ready by
- 2–3 business daysExpedited: within 24 business hours, +$150. Clock starts when complete plans pass intake (3:00 PM ET cutoff) · how it works
Clay, Nassau, Baker and Putnam
Per-county table4 counties · zone, design °F, permits, housing
| County · stations | Zone | Design °F | Permits | Median built | Single-family | Mobile | Electric heat |
|---|---|---|---|---|---|---|---|
| ClayJacksonville Cecil Field (Manual J) · Cecil Field (ASHRAE) | 2A | 94° / 32° | 1,240 #29 | 1996 | 74.0% | 11.1% | 94.6% |
| NassauJacksonville Cecil Field (Manual J) · Cecil Field (ASHRAE) | 2A | 94° / 32° | 887 #32 | 2000 | 65.9% | 16.0% | 92.3% |
| BakerJacksonville Cecil Field (Manual J) · Cecil Field (ASHRAE) | 2A | 94° / 32° | 99 #49 | 1996 | 63.2% | 30.5% | 94.6% |
| PutnamGainesville Regional Airport (Manual J) | 2A | 92° / 33° | 91 #53 | 1985 | 48.8% | 43.7% | 87.1% |
What it means for sizing
2 paragraphs · design temperatures, housing stock, equipment
Cecil Field supplies Clay, Nassau and Baker with the same pair Duval uses, 94°F and 32°F; Putnam's limits come from Gainesville Regional, 92°F and 33°F.2 Zone 2A throughout.1 A 62°F swing between design summer and design winter is wider than anywhere south of Ocala, which in our reading makes the heat pump's low-temperature capacity the first thing to check in Manual S here.
Clay and Nassau have the larger houses in this group, with median room counts of 6.2 and 6.0, and Nassau's stock is newer: 49.5% built since 2000, and 8.6% in 2020 or later alone.4 Putnam is the opposite case, with a 1985 median and 43.7% mobile homes.4 Clay issued 1,240 one-unit permits in 2025, Nassau 887.3
Worked example
2,300 sq ft house in Clay County → 28,240 Btu/h, 2.35 tons · illustrative
Illustrative · not a Manual J
A 2,300 sq ft four-bedroom frame home at Clay's 94°F and 32°F limits; Clay's 6.2-room median supports the size.4 Compare the heating line with any South Florida example.
| House | new single-storey frame home, Middleburg area |
|---|---|
| Conditioned area | 2,300 sq ft, 1 storey, 9 ft ceilings |
| Bedrooms / occupants | 4 / 5 |
| Glazing | 14% of floor area (322 sq ft), U 0.3, SHGC 0.25 |
| Walls / ceiling | R-13 walls, R-38 ceiling under a vented attic |
| Air leakage | 5 ACH50 |
| Ducts | in the attic, 8% gain allowance |
| Outdoor design | 94°F cooling / 32°F heating (Clay County, sourced) |
| Indoor design | 75°F cooling / 70°F heating |
| Design grains difference | 40 gr/lb (assumption) |
Illustrative only. A simplified block-load estimate with the inputs shown, not an ACCA Manual J, and not for permitting. A real calc goes room by room with your plans, orientation and equipment data.
Building departments
How we publish department checklists
Every county here has its own building department, and several cities run their own. We publish a department's checklist, contacts and quirks only after reading them on its official page, and each county here gets its own page once that's done. Until then, check with the county building department before you submit. Ordering works statewide today.
Northeast questions
3 answers · What design temperatures apply in Clay County?
What design temperatures apply in Clay County?
Clay uses Jacksonville Cecil Field's limits: 94°F at 1% cooling and 32°F at 99% heating, the same as Duval, Nassau and Baker. Those are RESNET's maximum county design conditions. At 32°F, heat-pump output at the design temperature matters, so look at the manufacturer's extended data in Manual S.
Is Nassau County's housing mostly new construction?
More than most of Florida: 49.5% of Nassau's housing units were built in 2000 or later, and 8.6% in 2020 or later, according to the 2020–2024 American Community Survey. Its median home dates from 2000. Nassau issued 887 permits for new single-family units in 2025.
Why is Putnam County's design data from Gainesville?
Putnam has no design station of its own in RESNET's county table, so it takes the values assigned by proximity, Gainesville Regional Airport: 92°F cooling and 33°F heating. Bradford, Columbia, Union and Alachua use the same station. That's normal for rural counties in the table.
Nearby and related
Price
One statewide price in all 67 counties. Building departments decide what they accept; we don’t guarantee approval. Revisions for plan-review comments on the same design are free.
Sources
4 primary references · numbered to match the citations
- 012023 Florida Building Code, Energy Conservation (8th Ed.), Table R301.1, climate zones by countyup.codes
- 02RESNET / ENERGY STAR, Appendix A: HVAC Design Temperature Limits by State and County (v4, 2019)resnet.us
- 03U.S. Census Bureau, Building Permits Survey, 2025 annual county data (new privately-owned 1-unit housing units)www2.census.gov
- 04U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates (B25001, B25003, B25018, B25024, B25034, B25035, B25040), via Census Reportercensusreporter.org