Comparisons · 1 min read
Polytunnel vs Greenhouse: Which Is Right for a UK Garden?
Polytunnel vs greenhouse compared for UK gardens: growing space, light, temperature, ventilation, wind, frost, cost, maintenance and crops, with a decision guide for small gardens, big plots and beginners.
A polytunnel gives you the most covered growing space for your money and is excellent for summer crops. A greenhouse, particularly a glazed one, holds light and heat better, looks tidier in a small garden and is the better choice for overwintering tender plants. Neither is better for everyone: the right one depends on how much space you have, what you want to grow and which months matter most to you.
Key takeaways
- The RHS describes polytunnels as highly cost-effective for summer crops such as tomatoes and cucumbers, but not usually economical to heat and keep frost-free over winter.
- Greenhouses are more versatile year-round; glass transmits the most light, polycarbonate a little less but won't shatter.
- Polytunnels suit bigger plots and bulk growing; greenhouses and lean-tos suit small gardens.
- Both need good ventilation. An unvented structure overheats fast on a sunny day, even in spring.
- Wind is a bigger risk for polytunnel covers; siting and anchoring matter for both.
What is a polytunnel?
A polytunnel is a series of curved hoops, usually steel, covered with a stretched sheet of polythene. The tunnel shape gives a lot of floor space and headroom for the cost, and doors at one or both ends (sometimes with mesh side windows) provide ventilation. Covers are usually UV-stabilised and replaced every few years, depending on the quality of the film and how exposed the site is.
What is a greenhouse?
A greenhouse is a rigid frame, typically aluminium, steel or timber, glazed with glass or polycarbonate panels. Freestanding greenhouses have glass on all sides; lean-to greenhouses sit against a wall, which saves space and can hold a little warmth from the building. Roof vents, louvres and doors control ventilation.
Polytunnel vs greenhouse at a glance
| Polytunnel | Greenhouse | |
|---|---|---|
| Growing space for the money | High | Lower per square metre |
| Light | Diffused through polythene; reduces as covers age and get dirty | Glass transmits the most; polycarbonate slightly less |
| Heat retention | Warms quickly, loses heat quickly | Better, especially glass and twin-wall polycarbonate |
| Winter use | Hardy winter crops such as salads; not for tender plants | Overwintering tender plants (with heating if needed) |
| Ventilation | Doors and mesh panels; long tunnels need ventilation at both ends | Roof vents and louvres |
| Wind | Cover can tear or lift if not tensioned and anchored | Panels can blow out on lightweight frames; needs a firm base |
| Maintenance | Cover replacement every few years; repair tape for small tears | Cleaning glazing; replacing broken panes or clips |
| Looks | Practical rather than pretty | Usually more of a garden feature |
| Best for | Large-scale summer growing, allotments, bigger gardens | Year-round growing, seedlings, tender plants, smaller gardens |
In short: choose a polytunnel if you want lots of growing space for summer crops on a budget and have room for it. Choose a greenhouse if you want year-round growing, need to overwinter tender plants, or have a small garden where looks and footprint matter.
Light and temperature
According to the RHS guide to choosing a greenhouse, glass transmits and holds more light than plastic glazing, which makes glass the most versatile option for seedlings and plants that need high light levels. Polycarbonate lets through a little less light but is lighter, cheaper and far less likely to shatter.
Polythene diffuses light, which spreads it evenly and reduces scorching, but it lets heat escape quickly once the sun goes down. In practice, a polytunnel can be very warm on a bright April afternoon and close to outdoor temperatures by dawn.
Frost and year-round growing
The RHS is clear on this point: polytunnels are not usually economical to heat and keep frost-free over winter. They can still be productive in winter for hardy crops such as lettuce and winter salads, but they aren't the place to overwinter tender plants such as pelargoniums or citrus. If protecting tender plants through a UK winter is a priority, a greenhouse, possibly with a small heater and bubble-wrap insulation, is the more realistic choice.
Ventilation
Both structures overheat quickly in sunshine. Greenhouses rely on roof vents and louvres; polytunnels rely on doors and side panels. A polytunnel with doors at both ends, or mesh windows along its length, moves air much better than one with a single entrance. Open up early on sunny mornings, even in spring, and close up in the afternoon to hold some warmth overnight.
Wind, rain and siting
- Polytunnels: a loose cover flaps and tears in gales. Tension it properly, bury or batten the edges, and anchor the frame firmly. Close doors in high winds.
- Greenhouses: need a level, solid base. Lightweight frames on exposed sites can lose panels in storms, so check the clips and fixings each autumn.
- Both: choose a sunny spot sheltered from the strongest winds, away from overhanging trees, with rain able to drain away from the base.
Cost considerations
Compare cost per square metre of growing space, not just the headline price. A walk-in tunnel covers a large area for a modest outlay, while a glazed greenhouse of the same footprint costs considerably more. Then add the running costs: a replacement polytunnel cover every few years, or occasional replacement panes, clips and vent openers for a greenhouse. Heating, if you plan any, is cheaper to run in a well-glazed greenhouse than in a single-skin tunnel.
What to grow in each
- Both do well with: tomatoes, cucumbers, peppers, chillies, aubergines, salad leaves, and early sowings of beans and courgettes.
- Polytunnel strengths: bulk summer crops in ground beds, winter salads, and extending the season at either end.
- Greenhouse strengths: seed-raising on staging, overwintering tender perennials, and light-hungry plants.
Which suits your garden?
| Your situation | Likely best fit |
|---|---|
| Small garden or courtyard | Lean-to greenhouse against a sunny wall, or a mini greenhouse |
| Large garden or allotment | Walk-in polytunnel for bulk crops |
| Beginner on a budget | Mini greenhouse or small polytunnel to learn the basics |
| Want to overwinter tender plants | Greenhouse, ideally with insulation and some heating |
| Mainly summer tomatoes and salads | Polytunnel |
| Very exposed, windy site | A sturdy, well-anchored structure on a firm base; shelter it if possible |
Three real starting points
- For balconies and patios: a 4-tier mini greenhouse (105 x 45 x 160cm) for seedlings and pots.
- For bigger plots: a 6 x 3 x 2m walk-in polytunnel with three roll-up doors and mesh windows for airflow.
- For small gardens with a spare wall: a 6 x 4ft lean-to polycarbonate greenhouse with an adjustable roof vent.
For more detail on siting, headroom and glazing, see our UK grower's guide to greenhouses and polytunnels.
Do you need planning permission?
Greenhouses and polytunnels in a domestic garden are usually treated as outbuildings, which in England can often go up under permitted development within limits on size, height and position. Rules differ in listed buildings, conservation areas and across the UK nations, so check the Planning Portal's outbuildings guidance or your local council before building anything large. Allotment sites often have their own rules on polytunnels, too.
Frequently asked questions
Is a polytunnel better than a greenhouse?
Not in every case. A polytunnel gives more growing space for the money and suits summer crops; a greenhouse holds heat and light better and suits year-round growing and tender plants.
Can you grow in a polytunnel in winter?
Yes, hardy crops such as winter salads grow well. The RHS notes polytunnels aren't usually economical to heat and keep frost-free, so they're not suited to overwintering tender plants.
Which is better for a small garden?
Usually a lean-to or small freestanding greenhouse, or a mini greenhouse on a patio. Polytunnels are most cost-effective at larger sizes.
Which is better for a beginner?
A mini greenhouse or small polytunnel is a low-cost way to learn about ventilation and watering under cover before committing to a larger structure.
How long does a polytunnel cover last?
It varies with the film quality, UV treatment and how exposed the site is. Check the manufacturer's stated lifespan and expect to replace the cover periodically.
Making your choice
Decide which season you care most about, measure the space you have, and choose the structure that fits both. You can compare mini greenhouses, polytunnels and lean-to greenhouses in our greenhouse collection.
Written and checked by the Hackerprice® editorial team. Product details were checked against our live catalogue when this guide was written. Growing guidance is drawn from the RHS, and planning guidance from the Planning Portal. Last updated: 30 September 2026.
Writes the buying guides at HACKERPRICE. No sponsored picks, no affiliate links.
