Polytunnel vs greenhouse: which is better for a UK garden?
A polytunnel gives you far more growing space for your money. A greenhouse holds heat better, lasts for decades and is easier to vent and keep tidy.
The short answer
Choose a polytunnel if you want the most growing space for your money, mainly grow vegetables and salads, and have room for a good-sized tunnel. Expect to replace the cover every 5–10 years.
Choose a greenhouse if space is tight, you raise lots of seedlings, want to heat in winter, or want something that lasts decades and looks tidy near the house.
Polytunnel and greenhouse compared
| Polytunnel | Greenhouse (aluminium, glass) | |
|---|---|---|
| Cost per m² (October 2026 examples) | About £29–£64, falling as the tunnel gets longer | About £97–£116, plus a base |
| Light | Depends on the film: about 90% for clear film; diffused, and less as it ages | The most direct light, especially in winter |
| Holding heat | Poorer, especially on clear nights | Better |
| Condensation | Drips from the roof onto plants unless the film is anti-fog | Runs down the glass to the gutters |
| Ventilation | Doors at each end; side or ridge vents as extras | Roof and side vents; vents can be thermostatically controlled |
| Wind | Cover must be tight and the frame anchored | Frame anchored to a level base |
| Lifespan | Frame about 15–20+ years; cover 5–10 years | Decades for the frame and glass |
| Ground | Can go on rough soil and gentle slopes | Needs a level, square base |
Cost per square metre
This is where a polytunnel wins clearly, and the gap grows with size.
In October 2026 First Tunnels listed its 10ft wide domestic tunnel at £594 for 10ft long (about 9.3m², so roughly £64 per m²), £754 for 20ft long (about £41 per m²) and £1,062 for 40ft long (about £29 per m²). Each extra 5ft of length added only about £74–£81.
A greenhouse costs more for each square metre, and the price climbs in step with the size. The same month, a Vitavia Venus 5000 8x6ft in 3mm horticultural glass was £509 for about 5m² of floor (roughly £100 per m²), and a Vitavia Neptune 8x12ft was £949 in horticultural glass or £1,144 in toughened glass for about 9.8m² (about £97–£116 per m²). Neither price includes a base. Greenhouse Stores says these greenhouses must sit on a raised plinth and sells Vitavia steel plinths at £89–£96; Gardensite lists a steel base frame for the Venus as an optional extra from £74.99.
Northern Polytunnels, which sells tunnels, puts it more bluntly: an 8x12ft polytunnel is on average two and a half times cheaper than a greenhouse of the same size.
Space and head height
A tunnel's curved sides cut usable space at the edges: you lose height exactly where the side beds are. Straight-sided or "high side" designs help. First Tunnels' 10ft wide tunnel has 3ft 2in straight sides and is 7ft high in the middle, enough for crop bars that carry tall tomatoes, cucumbers and beans.
Small greenhouses are lower than many people expect. The 8x6ft Venus is 1.24m to the eaves and 1.97m at the ridge, so you stoop at the sides.
Several forum posters say tunnels fill up fast, so buy the largest that fits. On a small plot the sums change. In one Grow Fruit and Veg thread, a gardener weighing up an 8x14ft space chose a glass greenhouse, mainly because it made collecting rainwater easier, and another reply judged glass the better value at that size.
Light
How much light a tunnel lets in depends on the film. Charles Dowding recommends standard light-diffusing horticultural polythene, which he says admits about 89% of daylight. First Tunnels lists 90% light transmission and 30% diffusion for its clear Super Therm film. Diffused light reaches plants more evenly from all sides. Glass gives the most direct light, which matters most for seedlings and winter growing.
Polythene loses light as it ages and goes milky: Greenhouse Stores says a cover passes 10–15% less light after 3–5 years. Glass has to be cleaned too, but it does not cloud with age.
Heat and frost
A greenhouse keeps heat better. Polythene lets more of the day's stored warmth escape as infrared on a clear night, so an unheated tunnel can get colder than a greenhouse just before dawn.
That matters most if you plan to heat. Heating a tunnel for tender plants costs more. For frost protection and hardy winter crops, a tunnel is fine: Charles Dowding grows winter salads in an unheated tunnel from October to spring.
Condensation and ventilation
Condensation is the most common complaint about tunnels. Water collects on the underside of the film and drips onto leaves, which encourages grey mould (botrytis). Anti-fog polythene contains an agent that, according to cover seller Elixir Gardens, makes droplets run off rather than drip. In a greenhouse, water runs down the glass to the gutters.
Ventilation is harder in a tunnel. Most rely on doors at both ends to pull a through-draught, with side vents or a ridge vent kit as extras. Dowding suggests 20–30ft as the length that ventilates most evenly, finds side vents unnecessary for vegetables in tunnels under about 40ft long, and leaves a gap of about 6 inches above each door so air keeps moving in winter without a cold draught at ground level. Greenhouses have roof and side vents, and can have thermostatically controlled opening panels, which amateur polytunnels generally do not.
Wind and anchoring
Both need anchoring in a British winter, and one forum poster warns that weights are usually inadequate. Greenhouse Stores calls wind the number one cause of polytunnel damage in the UK and says most home insurance policies exclude polytunnel wind damage, so check yours.
A tunnel fails when the cover loosens, flaps and tears, then the wind gets inside. Three things prevent it:
- A tight cover. Fit it on a warm, still day; polythene stretched in cold weather goes slack and is more easily damaged.
- Anti-hotspot tape on the hoops where the film touches metal, so the film does not weaken at those points.
- Proper foundations. On soil, foundation tubes are set in concrete, or driven in where the cover is buried in a trench. Anchor plates or long screw anchors are alternatives; base plates are for fixing to existing concrete or timber.
A greenhouse needs a level, square base it is fixed down to. See our guide to greenhouse bases. A tunnel can go straight onto soil and gentle slopes, and some can be moved later.
Lifespan and maintenance
A well-kept aluminium and glass greenhouse can last a lifetime. For the Vitavia Venus, Greenhouse Stores lists a 12-year warranty on the frame and base (excluding glazing and wind damage), and Gardensite a 10-year manufacturer's guarantee.
A tunnel has two lifespans. The frame of a good tunnel lasts about 15 years, according to Gardenfocused, or 20+ years if galvanised, according to Greenhouse Stores. The cover does not:
- Good covers are 720 gauge (180 micron), which Northern Polytunnels says most professional tunnels use, or the thicker 200 micron. Cheaper 150 micron covers last 4–6 years, according to Greenhouse Stores.
- First Tunnels guarantees its covers for at least five years (seven for its 200 micron Super Therm) and says covers can last 10 years or more.
- Charles Dowding replaces his every 5–8 years, depending on wind and how tight it was fitted.
Check the polythene is UV stabilised: First Tunnels says this is to stop it breaking down prematurely, and Dowding says film without a UV stabiliser can go brittle within a year. That is the main thing to check on a cheap tunnel. Some gardeners simply do not want the job of re-covering every few years.
If you prefer rigid glazing but want something tougher than glass, our polycarbonate vs glass greenhouse guide compares the two.
Do you need planning permission?
In England, greenhouses count as outbuildings and are usually permitted development, so no application is needed if:
- It is single storey, with eaves no higher than 2.5m.
- It is no higher than 4m overall with a dual-pitched roof, or 3m with any other roof.
- It is no higher than 2.5m if it is within 2m of a boundary.
- It is not in front of the main face (principal elevation) of the house.
- All outbuildings and extensions together cover no more than half the land around the original house.
You will need permission at the side of the house on designated land (conservation areas, National Parks, AONBs, the Broads, World Heritage Sites), anywhere in the garden of a listed building, and for flats and maisonettes. In National Parks, the Broads, AONBs and World Heritage Sites, outbuildings more than 20m from the house are also limited to 10m² in total.
A garden polytunnel is generally treated the same way. Most domestic tunnels are well under 2.5m high, so height is rarely the issue, but a large tunnel can draw objections because it looks commercial.
What grows best in each
- Polytunnel: summer crops in quantity (tomatoes, cucumbers, peppers, French beans, melons on crop bars), strawberries, and unheated winter salads and hardy greens.
- Greenhouse: seed-raising and bedding plants, tender plants kept frost-free over winter, and anything needing controlled heat and good winter light.
The difference is mostly scale: a tunnel suits growing in bulk, a greenhouse suits precision.
Which should you choose?
- Small garden with room for only a compact structure: a greenhouse, since a small tunnel loses much of its edge space to the curved sides. See our greenhouse guides.
- Room for a larger structure, mainly vegetables: a polytunnel gives far more space for the money. See our polytunnel guides.
- You will heat in winter: a greenhouse.
- Lots of seedlings in early spring: a greenhouse, for the light.
- Sloping or rough ground, or you may move house: a polytunnel.
- Exposed, windy site: either, but anchor it properly. For a tunnel, buy heavy-duty hoops and foundation tubes set in concrete.
- Near the house, children playing: a polytunnel, or a toughened glass or polycarbonate greenhouse.
Questions people ask
Is a polytunnel better than a greenhouse?
Not for everyone. A polytunnel gives considerably more growing space for the money, and the gap widens with size, and suits growing vegetables in quantity. A greenhouse holds heat better, is easier to ventilate, lasts decades and suits small gardens, seed-raising and heated growing.
How long does a polytunnel cover last?
Usually 5–10 years. Covers are typically 720 gauge (180 micron) or 200 micron polythene, and UK makers such as First Tunnels guarantee them for five to seven years. A tight fit, anti-hotspot tape on the hoops and a sheltered site all help a cover last longer.
Do you need planning permission for a polytunnel in your garden?
Usually not in England, as long as it meets the permitted development rules for outbuildings: single storey, no higher than 2.5m within 2m of a boundary, not in front of the house, and covering no more than half the garden with other buildings. Listed buildings, flats and designated land have tighter rules.
Are polytunnels colder than greenhouses in winter?
Generally yes, especially on clear frosty nights, because polythene lets more heat escape. An unheated tunnel still keeps off frost well enough for hardy winter salads and greens, but heating one for tender plants costs more than heating a greenhouse.
How do you stop condensation in a polytunnel?
Buy an anti-fog (anti-drip) cover, which is meant to stop droplets dripping on plants. Keep air moving with doors at both ends, and leave a small gap above each door in winter.
Sources
- Polytunnels vs greenhouses: how to decide, Northern Polytunnels
- Polytunnel cover (polythene and gauge), Northern Polytunnels
- How to choose between a polytunnel and a greenhouse, David Domoney
- Greenhouse vs polytunnel: which is better for a UK garden?, Greenhouse Stores
- Polytunnel and greenhouse comparison in the UK, Gardenfocused
- Polytunnels, advice on buying, Charles Dowding
- 10ft wide polytunnel, First Tunnels
- Polytunnel covers, First Tunnels
- Super Therm polythene (200 micron), First Tunnels
- Polytunnel cover sheeting, clear polythene, Elixir Gardens
- Vitavia 8x6 Venus 5000 greenhouse, horticultural glass, Greenhouse Stores
- Vitavia Venus 5000 6 x 8 ft greenhouse, Gardensite
- Vitavia 8x12 Neptune 9900 greenhouse, Greenhouse Stores
- Outbuildings: planning permission, Planning Portal
- Polytunnel vs Greenhouse (forum thread), Kitchen Garden forum
- Greenhouse or polytunnel? (forum thread), Grow Fruit and Veg forum
- Polytunnel advice please (forum thread), Allotments4all