# Sovereignty Module: Extend the Season

## Complete Greenhouse Construction: From Cold Frame to Year-Round Growing

Greenhouses extend growing seasons and enable food production in any climate. This campaign covers cold frames, hoop houses, greenhouse design, heating, and year-round growing strategies.

### Chapter 1: Season Extension Structures

| Structure | Cost | Difficulty | Temperature Gain | Season Extension | Lifespan |
|---|---|---|---|---|---|
| Row cover (fabric) | Very low | Very low | 2-8°F | 2-4 weeks | 1-3 seasons |
| Cold frame | Low | Low | 10-20°F | 4-8 weeks | 5-20 years |
| Hot bed (heated cold frame) | Low | Low-moderate | 20-40°F | 8-16 weeks | 5-20 years |
| Low tunnel (mini hoop) | Low | Low | 5-15°F | 4-8 weeks | 2-5 years |
| High tunnel (hoop house) | Moderate | Moderate | 10-25°F | 8-16 weeks | 5-15 years |
| Greenhouse (unheated) | Moderate-high | Moderate-high | 15-30°F | Year-round (mild climates) | 10-30 years |
| Greenhouse (heated) | High | High | Any (controlled) | Year-round (any climate) | 10-30 years |

### Chapter 2: Hoop House Construction

| Component | Material | Sizing | Cost |
|---|---|---|---|
| Hoops | EMT conduit (1-1.5 inch), PVC (1.5-2 inch), or steel pipe | Spacing: 4 ft on center | Low-moderate |
| Ground posts | Rebar or pipe driven into ground | 2 ft deep, inside hoop ends | Very low |
| Covering | 6-mil greenhouse poly (UV-stabilized) | Single or double layer | Low |
| End walls | Framed lumber + poly or polycarbonate | Full height, with door | Low-moderate |
| Base boards | Treated lumber (2×6 or 2×8) | Perimeter | Low |
| Hip boards | Lumber at base of hoops | Secures poly at sides | Low |
| Ventilation | Roll-up sides, end vents, ridge vent | Critical for temperature control | Low |

Hoop house construction (14×30 ft): 1) Level site, mark footprint. 2) Drive rebar stakes every 4 ft along both long sides (2 ft deep, 1 ft above ground). 3) Bend EMT conduit or PVC into arches, slip over opposing rebar stakes. 4) Install ridge pole (purlin) along top for stability. 5) Install base boards along sides. 6) Frame end walls with door. 7) Pull poly over hoops on a calm day. 8) Secure poly to base boards with wiggle wire channel or lath strips. 9) Install roll-up sides for ventilation (critical). 10) Add end wall poly or polycarbonate. 11) Total cost: $500-2,000 depending on materials.

### Chapter 3: Greenhouse Design

| Factor | Recommendation | Why |
|---|---|---|
| Orientation | Long axis east-west | Maximum south-facing glazing (Northern Hemisphere) |
| Glazing angle | Perpendicular to winter sun angle | Maximum light transmission in winter |
| Thermal mass | Water barrels, stone, concrete | Absorbs heat during day, releases at night |
| Insulation | North wall insulated (no glazing) | Reduces heat loss, reflects light inward |
| Ventilation | 15-20% of floor area in vents | Prevents overheating, controls humidity |
| Foundation | Insulated perimeter | Reduces ground heat loss |
| Glazing material | Double-wall polycarbonate or double poly | Better insulation than single layer |

Passive solar greenhouse: 1) Orient long axis east-west. 2) South wall: maximum glazing (glass or polycarbonate). 3) North wall: insulated, solid (no glazing), painted white or reflective inside. 4) Thermal mass along north wall: 55-gallon drums filled with water, painted black. 5) Water absorbs solar heat during day. 6) Water releases heat at night (moderates temperature). 7) Insulated foundation (rigid foam, 2-4 ft deep around perimeter). 8) Ventilation: ridge vent at top, low vents on south side. 9) This design can maintain above-freezing temperatures in zone 5-6 without supplemental heat.

### Chapter 4: Heating and Cooling

| Method | Cost | Effectiveness | Fuel | Best For |
|---|---|---|---|---|
| Thermal mass (water barrels) | Low | Moderate (buffer) | Free (solar) | Mild climates |
| Compost heating | Very low | Moderate | Compost materials | Supplemental heat |
| Rocket mass heater | Low | Good | Wood (small amount) | Cold climates, DIY |
| Propane heater | Moderate | Very good | Propane | Emergency/cold snaps |
| Electric heater | Moderate-high | Very good | Electricity | Small greenhouses |
| Wood stove | Low-moderate | Very good | Wood | Cold climates |
| Roll-up sides (cooling) | Very low | Very good | None | Summer ventilation |
| Shade cloth (cooling) | Low | Good | None | Summer heat reduction |
| Evaporative cooling | Low-moderate | Good (dry climates) | Water + electricity | Hot, dry climates |

### Chapter 5: Year-Round Growing

| Season | Strategy | Crops | Temperature |
|---|---|---|---|
| Spring | Start transplants, grow cool crops | Lettuce, spinach, broccoli, peas | 40-70°F |
| Summer | Ventilate heavily, grow warm crops | Tomatoes, peppers, cucumbers | 70-90°F |
| Fall | Extend harvest, plant cool crops | Lettuce, kale, carrots, radishes | 40-70°F |
| Winter | Grow cold-hardy crops, minimal heat | Spinach, mache, claytonia, kale | 25-50°F |

### Reference Card

1. Ventilation is more important than heating (overheating kills more greenhouse plants than cold; ventilate aggressively in warm weather). 2. Orient east-west (long axis east-west maximizes south-facing glazing for winter sun capture). 3. Thermal mass moderates temperature (water barrels absorb daytime heat and release it at night; the cheapest heating system). 4. Double layer glazing (double poly or twin-wall polycarbonate cuts heat loss nearly in half compared to single layer). 5. Insulate the north wall (no light comes from the north in winter; insulate it and paint the inside white to reflect light). 6. Cold-hardy crops in winter (don't try to grow tomatoes in January; grow spinach, kale, and lettuce that thrive in cold). 7. Hoop houses are cost-effective (a simple hoop house extends the season 2-3 months on each end for a fraction of greenhouse cost). 8. The greenhouse is a tool (it doesn't grow food by itself; you must manage ventilation, watering, and pest control actively).