Hoop House
An unheated or minimally heated greenhouse-style structure made from bent conduit or pipe covered with greenhouse poly film. Extends the growing season by 6-8 weeks on each end and, in mild climates, can enable year-round production.
A hoop house is a simple tunnel-shaped growing structure: arched metal conduit or PVC pipe covered with greenhouse-grade polyethylene film. No foundation, no permanent utilities, often no permit required in most jurisdictions. Compared to a cold frame, a hoop house is walk-in height and covers a much larger area. Compared to a permanent greenhouse, it’s a fraction of the cost and can be relocated.
The structure works by the same greenhouse principle: clear film transmits solar radiation in, which heats the soil and air inside; the film blocks the infrared wavelengths by which heated surfaces radiate heat back out at night. The thermal mass of the soil inside stores heat and releases it overnight.
Scale and Cost
A typical small farm hoop house: 14-30 feet wide, 48-100 feet long, 8-12 feet tall at the peak. A 14x48 foot house covers 672 square feet - enough for serious production. Construction materials (6-mil greenhouse poly, EMT conduit or steel pipe, ground stakes, end wall materials) cost $800-2,500 depending on size and material quality. Labor is the main variable; a 14x48 house can be assembled with two people over a weekend.
For home garden scale, smaller structures exist: 8-12 foot wide tunnel houses, walk-in caterpillar tunnels with metal hoops and poly, or Gothic-arch designs. A 10x20 foot tunnel costs $300-600 in materials.
Season Extension
In zone 6, a hoop house without supplemental heat extends the season by roughly 4-6 weeks in spring and 6-8 weeks in fall. Tomatoes can be transplanted in early April (zone 6) inside a hoop house versus mid-May outdoors. Fall tomato and pepper production continues well into October or November.
For cool-season crops (lettuce, spinach, kale, arugula), a hoop house enables year-round production in zone 6-7. Crops are planted in late August, harvested through December, then resume growth in February as days lengthen. The house doesn’t keep the interior above freezing on hard winter nights - crops must be cold-hardy - but it keeps temperatures from dropping as low and for as long as outdoor conditions.
Ventilation
The primary management challenge in a hoop house is temperature control. On a sunny winter day, interior temperatures can reach 80-90°F when outside is 30°F. Without ventilation, this cooks cool-season crops. Ventilation options:
- Roll-up sides: The standard for warm-season crop hoop houses. The bottom 2-4 feet of poly on the sides rolls up on a pipe, creating full sidewall ventilation. In winter, sides stay down; in summer, roll up.
- End wall vents and doors: Both end walls fitted with doors allow through-ventilation. Most hoop houses should have solid end walls with doors; poly-covered ends have less structural integrity.
For cool-season crops in winter, venting even 6-8 inches on mild sunny days is important.
Plastic Film
Standard greenhouse poly is 6 mil (0.006 inches thick). Look for “4-year poly” or “6-year poly” with UV stabilization - untreated poly degrades rapidly in UV exposure. Infrared (IR) blocking poly retains more nighttime heat than standard clear poly. Anti-drip additives prevent condensation from dripping on crops.
Poly needs replacement every 4-6 years. Replacing the cover on a 14x48 house costs $150-300 in materials.
Permits
In most residential jurisdictions, hoop houses are exempt from building permits if they’re temporary structures without permanent foundations. Verify local codes before building - some municipalities restrict unheated agricultural structures or have setback requirements. Purpose-built “high tunnels” used for farming are exempt from setback regulations in many agricultural zoning contexts.