Polycarbonate greenhouse buying guide

Not all polycarbonate glazing is the same

The word “polycarbonate” can describe thin clear panels, twin-wall sheets with insulating channels and thicker multiwall systems. Their light transmission, rigidity and replacement requirements differ. A useful product specification should identify the panel type and thickness, not simply call the greenhouse shatterproof.

Hybrid designs often use diffusing twin-wall panels in the roof and clearer panels in the walls. The roof softens direct overhead sun while the sides preserve outward views. This can be a practical balance, although every panel still depends on the frame's channels and retainers.

Twin-wall, multiwall and clear panels

Twin-wall sheets contain parallel internal channels. Those trapped air spaces slow heat transfer and scatter light. The channels must run so condensation can drain, and their ends need the correct combination of sealed and breathable tapes or caps.

Clear single-wall polycarbonate resembles glass from a distance and keeps the interior visible. It has less insulating air space and may flex more depending on thickness and support. Moulded panels can include specific edges that slide into a proprietary frame; they should not be replaced with generic sheet without approval.

UV protection and panel orientation

Sunlight degrades untreated plastics. Greenhouse-grade panels therefore use a UV-protective layer, often on one face. Installing that face inward shortens useful life and can lead to discolouration or embrittlement.

The temporary protective film normally identifies the UV side. Leave it in place until each panel's orientation is confirmed, then remove it at the stage specified in the instructions. Do not assume both faces are equivalent unless the manufacturer says so.

Panel retention matters in wind

Polycarbonate's low weight is helpful during delivery and assembly, but it also means wind can lift a poorly secured panel. The best defence is the complete system: straight frame channels, all specified clips or capping bars, undamaged panel edges, a square base and anchors that connect the frame to a stable foundation.

Do not use improvised screws through unsupported sheet. Polycarbonate expands and contracts with temperature, and a fixed hole can crack or leak if movement is not allowed. Use only manufacturer-approved reinforcements.

Before forecast high winds, close and latch doors and vents, remove loose objects and inspect known panel edges. A missing clip is easier to replace before a storm than after a panel has flexed out of its track.

Light, shade and temperature

Diffusing panels scatter incoming light so it reaches more leaf surfaces and creates fewer hard shadows. That is useful for dense staging and summer crops. It does not prevent overheating: even translucent glazing traps solar heat, and a closed greenhouse can reach damaging temperatures quickly.

Roof vents should release rising hot air, while the door or low-level vents admit replacement air. A single vent on a longer greenhouse may need supplementing. Removable external shading can reduce peak summer gain without permanently reducing winter light.

Twin-wall panels retain more heat than single glass, but gaps around doors, vents and panel edges still dominate in cold weather. If winter heating is planned, calculate it for the whole structure rather than using the panel's insulation claim alone.

Cleaning without damage

Polycarbonate is more prone to scratching than glass. Rinse loose grit first, wash with a soft sponge and compatible mild solution, then rinse clean. Work from a safe position; greenhouse roofs are not designed to carry a person's weight.

Avoid abrasive powders, stiff brushes, blades and solvents unless the manufacturer explicitly permits them. A pressure washer can drive water into channels and dislodge panels or seals. Clean gutters separately so dirty water is not forced back into panel ends.

Condensation inside the channels

A small amount of condensation can occur as temperature and humidity change. Correct panel orientation and end tapes let moisture drain while limiting dust and insects. Persistent algae or dirt inside the channels often points to failed sealing or incorrect installation.

Do not seal every end with an arbitrary household tape. Multiwall systems commonly require different treatment at the upper and lower edges. Replace failed tape with the specified type and refit caps so drainage paths remain open.

Base, assembly and replacements

Light glazing does not mean the greenhouse can sit loosely on soil. The base must remain level and anchored so the frame cannot rack. An included steel perimeter base is useful, but it still needs the approved connection to paving, concrete or ground anchors.

During assembly, avoid creasing sheets or crushing their channels. Keep protective film on while panels are moved and store them flat, out of wind. Record panel codes and dimensions from the manual so replacements can be ordered accurately later.

Who should buy polycarbonate?

It is a strong choice for self-builders, family gardens and sites where glass delivery would be awkward. It also suits gardeners who value diffused light and modestly improved heat retention more than crystal-clear views.

Choose toughened glass when transparency, scratch resistance and a traditional appearance lead the decision. Compare both in our glass versus polycarbonate greenhouse guide.

Final buying checks

Confirm panel construction and thickness, UV-face instructions, retention details, replacement availability, door width, vent provision, included base and anchor method. The best polycarbonate greenhouse is not simply the thickest panel: it is a coordinated frame-and-panel system that can stay square, sealed and secure on your site.

The Palram polycarbonate care guide gives material-specific precautions; check that it covers your sheet. Use our polycarbonate cleaning guide and replacement-glazing guide if ongoing care or repair access is part of the buying decision.