A greenhouse extends your season, protects tender plants and gives you a controlled space to raise seedlings and overwinter tender crops. But “greenhouse” covers everything from a small cold frame to a walk-in glasshouse, and the right choice depends on your space, climate and how you’ll use it. This is a buyer’s framework, not a one-size answer — use it to match a greenhouse to your garden.
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What a greenhouse actually does
A greenhouse traps solar heat and shelters plants from wind, frost and heavy rain, creating a warmer, more stable microclimate. It does not heat itself in winter without extra equipment, and on sunny days it can overheat fast — which is why ventilation“>ventilation matters as much as the structure.
Size: buy bigger than you think
The most common regret is buying too small. Plants, staging and pots fill the space quickly, and a larger volume holds temperature more steadily and overheats less abruptly. Balance that against your footprint, budget and any local rules. If space is tight, see small greenhouses“>small and compact greenhouses.
Frame materials
- Aluminium — light, rust-proof, low-maintenance and the most common; slim bars let in more light.
- Galvanised/powder-coated steel — very strong, good for larger or high-wind sites.
- Wood (cedar) — attractive and sturdy, but needs occasional maintenance.
- Resin/PVC — common on small hobby units; keep them well anchored.
Glazing: glass vs polycarbonate vs film
| Glazing | Light | Insulation | Durability | Best for |
|---|---|---|---|---|
| Horticultural glass | Highest clarity | Low (single pane) | Long-lived, can shatter | Permanent, sheltered sites |
| Twin/multi-wall polycarbonate | Diffused, good | Better (air gaps) | Shatter-resistant | Most home gardens, kids/pets, wind |
| Polythene film | Good when new | Low | Replace every few years | Budget, polytunnels, temporary |
For most home growers, polycarbonate greenhouses“>multi-wall polycarbonate is the practical middle ground: safer than glass, warmer, and diffuses light to reduce scorch.
Ventilation, siting and anchoring
- Ventilation — roof vents plus a louvre/side vent (and often a fan) are essential to dump summer heat and reduce disease-promoting humidity.
- Siting — a bright, sheltered, level spot with good winter light; avoid frost pockets and deep shade.
- Anchoring — secure to a base or ground anchors. Greenhouses are large sails; an unanchored one can be destroyed in a storm.
Accessories worth planning for
Staging/shelving, a max-min thermometer, automatic vent openers, shading (shade cloth“>shade cloth) for summer, and cold-season protection such as frost protection“>fleece and heaters. See the wider climate & season protection“>climate protection range.
Popular garden greenhouses
Greenhouse staging & shelving
Beginner vs advanced use
Beginners can do a lot with an unheated greenhouse: earlier and later seasons, seed raising, tomatoes and frost protection. Adding heating, automatic vents, shading and irrigation turns it into a year-round growing space — add those as your needs grow rather than all at once.
How to choose — quick checklist
- Pick the largest size your space and budget allow.
- Polycarbonate for safety/insulation; glass for clarity on sheltered sites.
- Insist on real ventilation (roof + side vents).
- Plan anchoring before delivery.
- Match frame strength to your wind exposure.
Quick questions
Glass or polycarbonate? Polycarbonate for most home gardens (safe, insulating, diffuses light); glass where you want maximum clarity on a sheltered site.
What size greenhouse should I buy? Bigger than you first think — space fills fast and larger volumes hold temperature more steadily.
Do I need heating? Not for season extension and frost protection in mild areas; you do for year-round warm-climate crops or hard winters.
Related guides
- Small greenhouses“>Small greenhouses · polycarbonate greenhouses“>polycarbonate greenhouses · greenhouse ventilation“>greenhouse ventilation
- Climate & season protection“>Climate & season protection · shade cloth“>shade cloth · frost protection“>frost protection
Greenhouse guides & equipment
Choose a greenhouse: kits“>kits · mini“>mini · small“>small · walk-in“>walk-in · lean-to“>lean-to · polycarbonate“>polycarbonate
Climate & equipment: climate control“>climate control · ventilation & fans“>ventilation & fans · heaters“>heaters · thermometers & hygrometers“>monitoring · shade cloth“>shade cloth · irrigation“>irrigation · shelving & benches“>shelving · propagation“>propagation
Growing guides: greenhouse growing“>greenhouse growing · what to grow“>what to grow · temperature“>temperature · ventilation“>ventilation · humidity“>humidity · cooling“>cooling · heating“>heating