First, so there is no confusion: we have not built, planted or tested the greenhouses on this site. You will not find a hands-on test or a "best buy" badge here. Instead we show you which numbers we use and how the score comes out of them, so you can check every score yourself.
Where the data comes from
- Maker websites: size, panel thickness, glass type, frame, vents, door, what comes in the box and the guarantee.
- UK retailers: when the maker leaves something out, we look at UK garden centres and specialist greenhouse shops. When two sources disagree, we say so in the notes on the product page.
- Amazon.co.uk: the price and the buyer reviews (stars and number of reviews). When a greenhouse has no Amazon price, we use the list price from the maker or a UK shop. Prices change often, and the shop always shows the current one.
- Missing figures: when nobody publishes a value, we write "not published". We never estimate a figure or fill one in.
The score: six parts, up to 2 points each
1. Glazing
- Plastic cover: 0.5 points. Plastic sheeting keeps little heat in and usually lasts a few seasons.
- Polycarbonate or acrylic: 2 points from 8 mm panels, 1.5 points from 6 mm, 1 point below that. If nobody publishes the panel thickness, this part drops out.
- Glass (including glass sides with a polycarbonate roof): toughened safety glass gets 1.5 points, because it is strong and breaks into small blunt pieces instead of sharp shards. Horticultural glass gets 1 point. If we know neither the glass type nor the thickness, the part drops out.
Read more in polycarbonate or glass and in our guide to twinwall polycarbonate.
2. Price per m²
We divide the price by the floor area. The area comes from the maker in m² where it is published. Otherwise we multiply length by width in centimetres, or in feet (1 sq ft is 0.0929 m²), and round to one decimal place.
| Price per m² | Points |
|---|---|
| up to £70 | 2 |
| up to £115 | 1.5 |
| up to £175 | 1 |
| more than £175 | 0.5 |
We use the Amazon.co.uk price first and the list price second. Without a price or an area, this part drops out.
3. Ventilation
We count roof vents and side vents or louvres. The door does not count, because every greenhouse has one.
| Vents | Points |
|---|---|
| 3 or more | 2 |
| 2 | 1.5 |
| 1 | 1 |
| none | 0.5 |
If the maker gives the roof vents but not the side vents (or the other way round), the unknown type counts as zero. If neither is known, the part drops out. Why vents matter so much is in the ventilation guide.
4. In the box
- Base included: 1 point
- Gutters included: 0.5 points
- Automatic vent opener included: 0.5 points
The maximum is 2 points. If the maker says nothing about any of the three, the part drops out. Why a base matters is in the greenhouse base guide.
5. Guarantee
| Guarantee | Points |
|---|---|
| 10 years or more | 2 |
| 5 years or more | 1.5 |
| 3 years or more | 1 |
| less than 3 years | 0.5 |
| none published | 0 |
This is the only part that never drops out. A guarantee nobody publishes is not one you can rely on, so it scores 0 and still counts. You keep your statutory rights under the Consumer Rights Act either way.
6. Buyer reviews
We only count the rating when a greenhouse has at least 20 reviews on Amazon.co.uk. Fewer than that tells you little.
| Rating | Points |
|---|---|
| 4.6 stars or more | 2 |
| 4.3 or more | 1.5 |
| 4.0 or more | 1 |
| below 4.0 | 0.5 |
How the parts become a score
We add up the points and divide them by the points that were possible. A part that drops out does not count against the greenhouse. We then scale the result to 0 to 10 and round it to one decimal place.
Example, the Halls Popular 6x8: 3 mm horticultural glass gives 1 point. The list price of £503.10 over 4.9 m² comes to about £103 per m², which gives 1.5 points. One roof vent gives 1 point. Only the gutters come in the box, which gives 0.5 points. The 12 year guarantee gives 2 points. There are no Amazon reviews, so that part drops out. That makes 6 of 10 possible points, a score of 6.0.
Example, the Palram Canopia Mythos 6x8: Palram does not publish the panel thickness, so glazing drops out. £449.31 over 4.6 m² comes to about £98 per m², which gives 1.5 points. One roof vent gives 1 point. The base and gutters give 1.5 points. The 5 year frame guarantee gives 1.5 points. 4.2 stars from 643 reviews gives 1 point. That makes 6.5 of 10 possible points, a score of 6.5.
What the score does not tell you
The score compares numbers on a spec sheet. It says nothing about how easy a greenhouse is to put up, how well the door runs after three winters or how the maker deals with a missing part. Read the reviews for that, and look at the notes on each product page.
How we earn money
When you buy through one of our links, we may earn a commission. It does not change the score, because the code works the score out from the data. The details are in our affiliate disclosure.