A polytunnel is a tunnel of polythene sheeting stretched over steel hoops, and a greenhouse is a rigid structure glazed in glass or polycarbonate panels on an aluminium or timber frame. A polytunnel is cheaper per square metre and faster to put up. A greenhouse lasts longer, holds heat better and suits a smaller, tidier plot close to the house.
Quick comparison
| Polytunnel | Greenhouse | |
|---|---|---|
| Typical cost for a similar footprint | Lower upfront | Higher upfront |
| Cover or glazing lifespan | 4 to 7 years (polythene) | 25 to 50+ years (glass or polycarbonate) |
| Heat retention | Lower, infrared escapes through polythene | Higher, especially glass |
| Growing space per pound | More | Less |
| Base needed | Often none, hoops go straight into soil | Usually yes, level hardstanding |
| Looks and property fit | Utilitarian, best tucked away | Garden feature, closer to the house |
| Cleaning | Easier, curved shape, no internal glazing bars | More corners and glazing bars to clean |
| Wind behaviour | Low profile, but cover can tear or billow | Depends on frame gauge and anchoring |
Is a polytunnel cheaper than a greenhouse?
Yes, for the same footprint a polytunnel almost always costs less to buy. The Outsunny 6 x 3m polytunnel we list is about £152 and covers 17.8 m², while the Palram Canopia Mythos 6x8 polycarbonate greenhouse is around £449 for 4.6 m². Per square metre that is roughly £8.50 for the polytunnel against about £98 for the greenhouse. The gap narrows over time because polythene covers need replacing every 4 to 7 years at £80 to £150 a time, while glass and polycarbonate panels are not routinely replaced.
Do polytunnels keep plants as warm as greenhouses?
No, a greenhouse generally holds heat better than a polytunnel. Glass and polycarbonate trap long-wave infrared radiation inside the structure, the classic "greenhouse effect", while polythene lets more of that heat escape. On a cold, clear night a polytunnel typically runs a few degrees cooler than a glazed greenhouse of the same size, which matters most for frost-tender crops in early spring and late autumn.
How long does each one last?
A galvanised steel polytunnel frame can last 15 to 20 years or more, but the polythene cover itself degrades under UV and weather and usually needs replacing every 4 to 7 years, depending on the grade of plastic and how exposed the site is. Glass panels on a well-built greenhouse frame can last 50 years or longer without losing clarity, and twin-wall polycarbonate typically carries a 10 to 15 year UV warranty before it starts to yellow. Over a 15-year ownership period this is the main place a greenhouse earns back some of its higher purchase price.
Which gives you more growing space for the money?
A polytunnel wins here by a wide margin. The First Tunnels 10x10ft polytunnel we list covers 9.3 m² for around £594, while the Halls Popular 6x8 glass greenhouse covers 4.9 m² for about £503. That is roughly £64 per m² for the polytunnel against £103 per m² for the greenhouse, and the gap grows further with bigger polytunnels: an 18 x 30ft model covers close to 50 m² at a fraction of what a greenhouse of that size would cost. If you want space to grow a serious amount of vegetables rather than a few growbags, a polytunnel gets you there for less.
Which handles wind and weather better?
Neither structure carries an official wind rating in the UK, since makers publish snow load far more often than wind resistance. In practice a polytunnel's low, curved shape gives wind less to catch, and the hoops are driven into the ground rather than perched on a raised base, but a worn or loose cover can still tear or billow in a storm. A greenhouse with a heavy-gauge frame bolted to a solid base, such as the Vitavia Venus 5000, resists wind well, but a light frame on paving slabs does not. The frame, the base and how it is anchored matter more than which type you pick. Our windy garden guide covers this in more depth.
Which is quicker and easier to put up?
A basic polytunnel is usually the faster build. Pushing galvanised hoops into prepared ground and stretching the cover over them is a job two people can finish in a day, and no hardstanding is required first. A glazed greenhouse takes longer: you need a level base ready before the frame goes up, then the panels have to be fitted one at a time without cracking them, which is typically a weekend job or longer for an 8x10ft model. Our greenhouse base guide covers what each base type involves.
Which suits a smaller garden close to the house?
A greenhouse. Its straight sides, tidy footprint and choice of colours (grey, green, black or natural aluminium) make it easier to place as a garden feature near a patio or back door, and most UK manufacturers size them specifically for suburban plots from 6x4ft upwards. A polytunnel's curved profile and utilitarian polythene skin work better tucked along a fence or at the back of a larger plot, away from the house, where appearance matters less than growing space.
Do I need planning permission for either?
Usually not. Both a polytunnel and a greenhouse normally fall under the same permitted development rules as other garden structures: broadly, a maximum ridge height of 2.5 metres within 2 metres of a boundary, and the structure should not take up more than half the garden once combined with other outbuildings. Rules vary between councils and are different again in conservation areas or for listed properties, so check with your local planning department before building anything large. See our planning permission guide for the detail.
So which should you choose?
Pick a polytunnel if you want the most growing space for your budget, you are growing a serious quantity of vegetables, and you have a larger plot where looks matter less. Pick a greenhouse if you want a structure that lasts decades without a new cover, holds heat better through a cold spring, and needs to look at home in a smaller garden near the house. Many experienced growers end up with both: a polytunnel for bulk crops and a greenhouse for propagation, tender plants and overwintering.
Tips before you decide
- Measure the plot first, not the structure. A 10x10ft polytunnel and a 6x8ft greenhouse take up very different amounts of space for a similar price.
- Budget for the base on a greenhouse and for ground anchors on a polytunnel. Neither price above includes it.
- Check your council's rules before you commit to a large structure near a boundary.
- Think about replacement cost. A polytunnel cover is a recurring cost every few years; a greenhouse's panels usually are not.
Compare the models above under polycarbonate greenhouses and glass greenhouses, read the greenhouse size guide to work out what fits your plot, or use the greenhouse finder to filter by type and budget.
Frequently asked questions
Is a polytunnel cheaper than a greenhouse? Yes, for the same footprint a polytunnel is almost always cheaper to buy, often by half or more. The gap narrows over 10 to 15 years of ownership because polythene covers need replacing every 4 to 7 years, while glass and polycarbonate panels usually do not.
Can I grow tomatoes in a polytunnel instead of a greenhouse? Yes. Tomatoes grow well in either, and a polytunnel's extra floor space often suits a bigger crop better. The main difference is early-season warmth: a greenhouse holds heat slightly better on cold nights, which can bring an earlier start in spring.
Do polytunnels need planning permission in the UK? Usually not, under the same permitted development rules that apply to greenhouses: broadly a 2.5 metre ridge height limit within 2 metres of a boundary, and no more than half the garden covered by outbuildings. Always check with your local council for anything larger or near a boundary.
How often do you need to replace a polytunnel cover? Most polythene covers last 4 to 7 years before they need replacing, depending on the thickness of plastic and how exposed the site is. A new cover typically costs £80 to £150 depending on the tunnel's size.
Is it easier to heat a polytunnel or a greenhouse? A greenhouse is easier and cheaper to heat because glass and polycarbonate retain warmth better than polythene. A polytunnel loses heat faster, so keeping it frost-free through winter usually costs more in heater running time. See our greenhouse heating guide for the options.
Can a polytunnel go directly on grass or soil? Yes, which is one of its advantages. The steel hoops are driven straight into the ground, so no paving or concrete base is needed, unlike most greenhouses, which need a level hardstanding.
Which lasts longer, a polytunnel or a greenhouse? The frame of either can last 15 to 50 years depending on the material, but a polytunnel's polythene cover is the weak point, needing replacement every 4 to 7 years. A greenhouse's glass or polycarbonate glazing typically lasts 10 to 50+ years without being swapped out.
