| Type | Best For | Cost Range | Difficulty |
|---|---|---|---|
| Lean-to | Limited space, attached to building | $$$ | Moderate |
| Freestanding A-Frame | Traditional design, good drainage | $$$$ | Moderate-High |
| Gothic Arch | Maximum light, commercial use | $$$$$ | High |
| Hoop House | Budget-friendly, season extension | $$ | Low |
| Cold Frame | Small scale, seedling protection | $ | Very Low |
Inputs
Result
Floor Area: 120 sq ft. Growing Space: 102 sq ft. Glazing Area: ~279 sq ft (end walls 2x10x7=140 + roof 2x5.77x12=138.6). Heating: ~4,178 BTU/hr (279 x 0.6 x 25). Plant Capacity: ~408 plants (6" pots). This compact greenhouse provides excellent space for home gardening with moderate heating costs due to insulated polycarbonate glazing.
Inputs
Result
Floor Area: 280 sq ft. Growing Space: 238 sq ft. Glazing Area: ~608 sq ft (end walls 2x14x6=168 + hoop roof PI*14/2*20=440). Heating: ~29,176 BTU/hr (608 x 1.2 x 40). Plant Capacity: ~952 plants. A cost-effective hoop house for season extension. Higher heating needs due to single-layer film and large glazing area.
Inputs
Result
Floor Area: 600 sq ft. Growing Space: 510 sq ft. Glazing Area: ~1,300 sq ft (end walls 2x20x10=400 + curved roof 30x20x1.5=900). Heating: ~35,750 BTU/hr (1300 x 0.5 x 55). Plant Capacity: ~2,040 plants. A large commercial-style greenhouse. Double glass keeps heating manageable despite the large glazing area in very cold climates.
Heating needs depend on glazing area, material U-value, and temperature differential. Single-pane glass requires about 1.1 BTU/hr per sq ft per degree of temperature difference, while double-pane glass needs only 0.5 BTU/hr. A 240 sq ft greenhouse in a cold climate (40 degrees F differential) with double-pane glazing needs approximately 4,800 BTU/hr.
Double-pane glass offers the best insulation (R-2) and longevity, but costs more. Polycarbonate twin-wall provides good insulation (R-1.7) at lower cost and better impact resistance. Polyethylene film is most economical but needs replacement every 3-4 years and has poor insulation (R-0.8).
Plant capacity depends on plant size and growing method. For 6-inch pots, estimate 4 plants per sq ft of growing space. Larger pots (1 gallon) fit about 2 per sq ft, while seedling trays can hold 10-15+ per sq ft. A 200 sq ft greenhouse typically provides 170 sq ft of growing space, accommodating 680+ small potted plants.
Hoop houses and cold frames are ideal for beginners due to low cost and simple construction. Hoop houses provide season extension for $2-4 per sq ft, while cold frames protect seedlings for under $100. Freestanding A-frame greenhouses offer better control but require more investment and building skill.
Glazing area includes all transparent surfaces - walls and roof. For an A-frame, calculate both end walls (2 x width x height) plus both roof slopes. For a hoop house, calculate end walls plus the curved surface area. A 12' x 20' A-frame with 8' walls has approximately 469 sq ft of glazing (end walls: 192 sq ft + roof slopes: 277 sq ft).
Most home gardeners find 8' x 10' to 12' x 20' greenhouses ideal, providing 80-240 sq ft. This size offers enough space for diverse growing without overwhelming maintenance. Smaller 6' x 8' units work for seedling starting, while 12' x 24' or larger suits serious production or commercial growing.
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Last Updated: Feb 13, 2026
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