# Sovereignty Module: Extend the Season

## Complete Greenhouse Construction, Season Extension, and Protected Growing Guide

Greenhouses extend the growing season by months, enabling food production year-round in cold climates. This campaign covers design, construction, heating, and management.

### Chapter 1: Season Extension Methods

| Method | Temperature Gain | Cost | Complexity | Season Extension |
|---|---|---|---|---|
| Row cover (floating) | +4-8°F | Very low | Very low | 2-4 weeks each end |
| Cold frame | +10-20°F | Low | Low | 4-8 weeks each end |
| Hoop house (unheated) | +10-15°F | Low-moderate | Low-moderate | 6-10 weeks each end |
| Greenhouse (unheated) | +15-25°F | Moderate-high | Moderate | 8-12 weeks each end |
| Greenhouse (heated) | Controlled (any) | High | High | Year-round growing |
| Underground greenhouse (walipini) | +20-30°F (stable) | Moderate | Moderate-high | Year-round (passive) |

### Chapter 2: Greenhouse Design Principles

| Principle | Rule | Reason |
|---|---|---|
| Orientation | Long axis east-west | Maximum south-facing glazing for winter sun |
| Slope (roof) | Perpendicular to winter sun angle (latitude + 15°) | Maximum light transmission in winter |
| North wall | Insulated (not glazed) OR thermal mass | No useful winter light from north. Insulate or store heat. |
| Ventilation | 15-25% of floor area in vents (ridge + side) | Prevents overheating, controls humidity |
| Thermal mass | 2-5 gallons water per sq ft of glazing | Stores daytime heat, releases at night |
| Foundation | Insulated below frost line | Prevents ground heat loss |
| Size | Minimum 8×12 feet (practical minimum) | Smaller = harder to regulate temperature |
| Height | 8+ feet at ridge | Hot air rises — tall = cooler at plant level |

### Chapter 3: Glazing Materials

| Material | Light Transmission | R-Value | Lifespan | Cost | Best For |
|---|---|---|---|---|---|
| Single glass | 90% | R-0.9 | 50+ years | High | Permanent greenhouse (cold climates need double) |
| Double glass (insulated) | 80% | R-2.0 | 50+ years | Very high | Cold climates, heated greenhouses |
| Polycarbonate (twin-wall) | 80% | R-1.5 to R-2.5 | 15-20 years | Moderate | Best all-around (light, strong, insulating) |
| Polyethylene film (6 mil) | 85-90% | R-0.8 (single) / R-1.5 (double) | 1-4 years | Very low | Hoop houses, temporary structures |
| Fiberglass (corrugated) | 75-85% | R-0.8 | 10-15 years | Low-moderate | Durable, hail-resistant |

### Chapter 4: Heating Systems

| Method | Fuel | Cost to Run | Complexity | Best For |
|---|---|---|---|---|
| Thermal mass (water barrels) | Free (solar) | None | Very low | Mild climates, buffer only |
| Compost heating (hot bed) | Organic waste | None | Low-moderate | Spring start, propagation |
| Rocket mass heater | Wood (small amount) | Very low | Moderate-high | Cold climates, off-grid |
| Wood stove | Wood | Low | Low | Cold climates, available wood |
| Propane/natural gas heater | Gas | Moderate-high | Low | Reliable backup, commercial |
| Electric heater | Electricity | High | Very low | Small greenhouses, backup |
| Underground air tubes (GAHT) | Free (earth heat) | None (fan electricity) | Moderate | Year-round passive heating/cooling |

Compost hot bed: Fill raised bed with 18-24 inches of fresh horse manure + straw. Top with 6 inches of soil. Decomposition generates 120-160°F for 4-6 weeks. Plant directly in soil above. Provides bottom heat for early starts.

### Chapter 5: Walipini (Underground Greenhouse)

| Step | Action | Specification | Details |
|---|---|---|---|
| 1 | Excavate pit (6-8 feet deep) | Length east-west, width 10-20 feet | Below frost line = stable 50-55°F year-round |
| 2 | North wall: vertical, insulated or thermal mass | Full height (6-8 feet) | Reflects light, stores heat |
| 3 | South wall: shorter (3-4 feet above grade) | Angled glazing facing south | Maximum winter sun penetration |
| 4 | Roof: glazed (south slope only) | Polycarbonate or polyethylene | Angle = latitude + 15° for winter optimization |
| 5 | Drainage: French drain around perimeter + sump | Gravel + perforated pipe | Underground = water table risk. Drainage critical. |
| 6 | Ventilation: ridge vent + underground air tubes | Passive or fan-assisted | Prevents overheating in summer |
| 7 | Stairs/ramp entry | On east or west end | Access without losing heat |

Advantages: Earth-sheltered = stable temperature (50-55°F year-round without heating). Only needs to add 10-20°F for tropical plants. Minimal fuel. Works in extreme cold climates (-40°F outside, still growing inside).

### Chapter 6: Greenhouse Management

| Task | Frequency | Purpose | Method |
|---|---|---|---|
| Ventilation | Daily (open when >80°F inside) | Prevent overheating, control humidity | Open ridge vents + side vents |
| Watering | Daily-every other day | Plant hydration | Morning watering (allows drying before night) |
| Temperature monitoring | Continuous (min/max thermometer) | Track conditions | Record daily highs and lows |
| Pest monitoring | Weekly | Early detection | Inspect undersides of leaves, sticky traps |
| Soil fertility | Monthly | Maintain nutrition | Compost tea, organic fertilizers |
| Glazing cleaning | Seasonally | Maximum light transmission | Wash inside and outside |
| Thermal mass management | Daily (passive) | Heat storage/release | Uncover water barrels during day, cover at night |

### Reference Card

1. Orient long axis east-west. Maximum south-facing glazing. Insulate north wall.
2. Ventilation: 15-25% of floor area. Ridge vent (hot air out) + side vents (cool air in). Prevents overheating.
3. Thermal mass: 2-5 gallons water per sq ft glazing. Black barrels on north wall. Free nighttime heat.
4. Twin-wall polycarbonate: best all-around glazing. R-1.5 to R-2.5, 80% light, 15-20 year life, lightweight.
5. Walipini: dig 6-8 feet deep, glaze south slope only. Earth provides 50-55°F baseline year-round.
6. Compost hot bed: 18 inches fresh horse manure + straw under 6 inches soil. 120-160°F for 4-6 weeks.
7. Winter growing (unheated): lettuce, spinach, kale, chard, Asian greens, carrots survive to 20°F with protection.
8. Overheating kills more greenhouse plants than cold. Ventilate aggressively above 80°F.