For community food production build a high tunnel rather than a small greenhouse: the carrier guide gives 20-30 feet wide, 50-100 feet long and 10-12 feet tall at the peak, a frame of bent conduit, cattle panels or heavy wire, a long axis east-west in the Northern Hemisphere, and doors at both ends for airflow. An unheated tunnel buffers weather but does not make winter into summer, so choose crops for it and plan ventilation first. Cover it with film or salvaged glazing and check the frame for snow and wind before the first storm.
A high tunnel, or hoop house, is a large walk-in greenhouse made of a hooped frame covered with plastic or glazing, used to grow food in a protected space through cold weather.
A Walk-In Tunnel Is More Stable Than A Frame And Needs More Planning
The carrier guide (Four-Season Growing & Season Extension) tells readers to forget the hobby greenhouse for community food production and build a high tunnel, 20-30 feet wide and 50-100 feet long, 10-12 feet tall at the peak, with a metal conduit, cattle panel or heavy wire hoop frame, salvaged greenhouse plastic or several layers of clear sheeting, a long axis east-west for the most winter sun, framed end walls and doors at both ends.
A large volume of air changes temperature more slowly than a cold frame, which makes it more forgiving but also slower to cool when you want it to. The same sun that warms it can overheat it, and the same enclosed air that holds heat holds moisture. The principles of Ventilation and Temperature Management apply, scaled up.
What You Need
- Land that is level, well drained and sunny, with the long axis east-west (Solar Orientation & Geometry explains the sun geometry).
- Frame material (conduit, cattle panels, wire, timber).
- Cover: film, glass or rigid sheet (Plastic Film & Alternatives, Salvaged Glass).
- Doors, vents and a way to water.
Method
Step 1: Choose the site well away from tall trees and out of frost hollows (Cold Air Drainage & Frost Pockets).
Step 2: Orient the long axis east-west. Mark true east-west with a shadow stick (Shadow Stick).
Step 3: Build the frame and cover (Post-Collapse Greenhouse Construction).
Step 4: Plan the interior with beds and paths, a water source and a place for thermal mass (Thermal Mass Heating).
Step 5: Choose the crops (Crop Selection for Protected Growing).
Common Mistakes
- Building too small to be useful or too large to ventilate — match size to the crew and the vents.
- No plan for snow — wet snow collapses hoops.
- Putting it where it shades or is shaded — a tunnel in the shadow of trees gains little.
What’s Next
- Learn next: Post-Collapse Greenhouse Construction — how to build one
- Combine with: Greenhouse Structures — smaller, framed alternatives