How we score greenhouse kits

We review greenhouse kits from the makers' and dealers' published specifications and prices, read on the date shown on each page (last on November 12, 2026). Every kit gets one score out of 10, and that score is the same on every page of the site.

The eight criteria

How each criterion is scored

Each criterion is turned into a score out of 10 by straight-line interpolation between the anchor points below, capped at both ends.

• Price per square foot: the dated US price divided by the floor area, compared with the median of our list ($22.49 per sq ft). Ratio to the median: 0.35× → 10, 0.6× → 9, 1× → 7, 1.6× → 5, 2.6× → 3.
• Panels: polycarbonate thickness in mm, roof and walls averaged: 0.8 mm → 3, 4 mm → 6.5, 6 mm → 7.5, 10 mm → 9.5. Twin-wall and thicker sheets hold heat better. Tempered glass scores 6: the most light, less insulation than thick twin-wall.
• Snow load (lb/ft², converted from psf or kg/m² when needed): 8 → 3, 15 → 6, 20 → 7.5, 30 → 9, 40 → 10.
• Wind rating (mph): 27 → 3, 45 → 5, 56 → 6.5, 65 → 8, 90 → 9.5, 115 → 10.
• Warranty (years; frame and panel terms averaged when they differ): 1 → 3, 3 → 5, 5 → 6.5, 10 → 8.5, 12 → 9.5, 15 → 10.
• Headroom (peak height, inches): 72 in → 4, 80 in → 6, 90 in → 7.5, 100 in → 9, 106 in → 10.
• Ventilation in the box (roof vents, windows and louvers included): 0 → 2, 1 → 6, 2 → 8, 3+ → 10.
• Base or anchoring in the box: steel base included → 10, ground anchors → 7, no base → 4.

When a spec isn't published

A criterion the maker or dealer doesn't publish scores 2/10. We can't credit what isn't stated, and a kit should not win on silence. That is why, for example, the Rion Grand Gardener ranks last: we found no snow, wind or warranty figure for it. A kit with no published price, or fewer than 5 published criteria, gets no score at all.

From raw score to displayed score

The raw score is the weighted average of the eight criteria. Every kit we list is a serious, current option, so we show it on an editorial scale: displayed score = 7.5 + 0.6 × (raw score − 4.5), kept between 7.5 and 9.6. The order of the raw scores never changes. Labels: Excellent from 9.0, Very good from 8.5, Good from 8.0, Fair below 8.0.

Rankings by need

Each ranking puts the same criteria in a different order of importance. The weights change the order of the list, never the score: each kit keeps its one overall score everywhere.

Where the data comes from

• Specs and prices come from the official product page or, for Palram-Canopia and Rion (no online sales in the US), from the US dealer Planet Greenhouse. Every review links its sources.
• Prices are the price you could pay on the date shown, in US dollars. When a seller shows a discount, we use the discounted price and say so.
• When two figures disagree on the same page, we use the more conservative one and mention both.
• We don't use user ratings or star averages from stores.

Current scores

Questions about the method? Write to [email protected].