Hoop House Calculator
Design your hoop house or high tunnel greenhouse with confidence. Enter width, length, and peak height, then select hoop spacing, cover type, climate zone, and end wall options. Get the exact arc length per hoop, number of hoops needed, total pipe and purlin lengths, cover material area, interior volume, and floor area. The calculator also recommends heater size in BTU/hr and kW based on your climate and cover type, plus estimated material costs.
Width of the greenhouse from ground to ground (base width)
Length of the greenhouse
Height at the center/peak of the hoop
Closer spacing for snow loads; 4 ft for standard
Affects recommended heater size and insulation
How do I calculate the surface area of a hoop house?
A hoop house is essentially a half-cylinder (quonset shape). The arc length of one hoop = π × (width ÷ 2) for a semi-circle, but for raised-wall hoops use the arc formula: arc = 2 × height + (width - 2 × height) × π ÷ 2. Total cover area = arc length × total length + end wall areas. For a 14×24 ft hoop house with 8 ft peak: arc ≈ 22 ft, cover area ≈ 22 × 24 = 528 sq ft, plus two end walls ≈ 2 × 96 = 192 sq ft. Total ≈ 720 sq ft of cover material.
What size heater do I need for my hoop house?
Heater size depends on volume, cover type, temperature lift needed, and climate. Basic rule: 5,000-8,000 BTU/hr per 100 sq ft for moderate climates (freeze protection). For a 14×24 ft hoop (336 sq ft): 17,000-27,000 BTU/hr for freeze protection. For growing warm-season crops (55°F minimum when 20°F outside), double that. Electric heaters: 1 kW = 3,412 BTU/hr. Propane: 20-lb tank at 30,000 BTU/hr lasts about 24 hours at full output. Adding thermal curtains reduces heat loss by 30-50%.
What is the best plastic for a hoop house?
6-mil UV-stabilized polyethylene is the standard for most hoop houses. It lasts 2-4 years with proper installation. Four-mil is lighter and cheaper but tears more easily and lasts only 1-2 years. Eight-mil is heavier-duty but reduces light transmission (an issue in northern climates). Woven greenhouse fabric lasts 5-10 years but costs 3-4× more. Double-layer inflated polyethylene (two layers with a small air gap) provides R-2 insulation vs R-0.8 for single layer, saving 30-40% on heating costs.
How many hoops do I need for my greenhouse?
Number of hoops = (length ÷ spacing) + 1. For a 24-ft house with 4-ft spacing: (24 ÷ 4) + 1 = 7 hoops. Each hoop uses one 20-ft length of 1-inch EMT conduit or PVC pipe (for a 14-ft wide hoop). Total conduit needed: 7 × 20 = 140 ft. Cross-bracing: 2-3 purlin runs the full length (24 ft each) for stability. For heavy snow areas, reduce spacing to 2-3 ft. Corner bracing at each end and diagonal bracing in the end hoops prevent racking.