South Zone
The furnace. Hottest at solar noon, highest natural light, driest VPD. Where the exhaust fans live and the hex tapers to its narrowest point. This is pepper and tomato country.
Climate Profile
| Metric | Value | Context |
|---|---|---|
| Peak temperature (hot day) | 100.4°F | March 25, 88°F outdoor |
| Avg peak vs greenhouse avg | +5-9°F | Consistently the hottest zone at noon |
| Overnight retention | 2-4°F above north | Concrete slab stores solar heat |
| VPD at peak | Highest in greenhouse | Exhaust fans pull humid air out here |
| CO₂ | Elevated midday (+150 ppm) | Soil microbial activity from floor pots |
Why It’s Hottest
Three factors stack:
- Hex taper — the south wall is the narrowest (~8-10 ft), concentrating solar gain per square foot of floor
- Exhaust fans — both Ken Brown 18” fans are mounted here. They move 4,900 CFM but also pull hot air toward the south zone
- Peak solar angle — at solar noon, the south-facing surfaces receive maximum radiation
The Heat Spot Rotation
South isn’t always hottest. The heat rotates through the day:
- Solar noon (12 PM): South is hottest (100°F+)
- 2 PM: North catches up (93.6°F — house thermal mass releasing stored heat)
- Late afternoon: West takes the lead (setting sun on the longest wall)
- Overnight: South retains heat from concrete slab (2-4°F above north)
Physical Layout
| Position | Contents | Water Access |
|---|---|---|
| SOUTH-SHELF-T1 through T4 | 4 shelf bays, top tier | Wall drip (shared zone) |
| SOUTH-SHELF-B1 through B4 | 4 shelf bays, bottom tier | Wall drip (shared zone) |
| SOUTH-FLOOR | Canna lilies in large pots | Individual drip heads from wall drip line |
Wall Structure
The south wall is one of the small angled walls of the hexagon (~8-10 ft wide). Two shelf bays on the southeast angled wall and two on the southwest angled wall flank the narrower south face.
Equipment
- Exhaust Fan 1: Ken Brown 18” shutter exhaust, 2,450 CFM, 52W (pcf_out_2 pin 3)
- Exhaust Fan 2: Ken Brown 18” shutter exhaust, 2,450 CFM, 52W (pcf_out_2 pin 4)
- South Misters: 6 heads, 30 nozzles, wall-mounted in 2 rows. Most effective zone (0.15 kPa avg VPD drop per pulse)
Water Systems
| System | Type | Control | Notes |
|---|---|---|---|
| Wall drip (clean) | Scheduled, daily 6 AM × 10 min | pcf_out_1 pin 4 | Shared with west zone — ONE zone |
| Wall drip (fert) | On-demand | pcf_out_2 pin 0 + master | Same heads, fert supply path |
| South misters (clean) | VPD-triggered pulse | pcf_out_1 pin 3 | 60s on / 45s gap |
| South misters (fert) | Manual | pcf_out_1 pin 2 | Available for fertigation |
Sensor Coverage
| Sensor | Address | Interval | Accuracy |
|---|---|---|---|
| Temperature | Modbus addr 4 (Tzone SHT3X) | 10s | ±0.3°C |
| Relative Humidity | Same probe | 10s | ±2% RH |
| VPD | Derived on ESP32 (Magnus formula) | 10s | Calculated |
| Soil moisture | Modbus addr 7 (DFRobot SEN0601) | 30s | %VWC |
| Soil temp | Same probe | 30s | °F |
| Soil EC | Same probe | 30s | µS/cm |
Recommended Crops
| Crop | Why South Zone | Notes |
|---|---|---|
| Peppers (habanero, superhots) | Tolerates 100°F+, loves heat | Floor or lower shelves |
| Tomatoes | Needs highest DLI, tolerates heat | Floor pots with support |
| Canna lilies | Already here, established | Need fertilizer for spring outdoor placement |
| Heat-tolerant herbs (oregano, thyme) | Tolerant of dry + hot | Upper shelves |
Avoid: Lettuce, cilantro, spinach — anything that bolts above 80°F. The south zone exceeds 80°F routinely from March through October.
→ See Climate at 5,000 Feet for the full thermal analysis. → See Cooling & Ventilation for exhaust fan details. → See All Zones