Six-millimetre twin-wall polycarbonate is a common option for backyard greenhouses. It is light, diffuses sunshine and has an air channel between its two skins. But is it enough for a greenhouse in Canada? The answer depends on what βenoughβ means for your climate, growing plans and the structure holding the panels.
What Is Twin-Wall Polycarbonate?
Twin-wall polycarbonate consists of two thin outer layers joined by internal ribs. The channels between them hold air, which helps limit heat transfer compared with a single solid sheet. The material is lighter than glass and generally resists impact well, but it can scratch and must be installed as specified by its manufacturer.
Panel specifications vary. Compare actual thickness, wall construction, weight, light transmission, thermal performance and warranty details for the product being offered rather than assuming all 6 mm panels are identical.
Is 6 mm Enough for Winter Growing?
A 6 mm twin-wall roof can help retain some heat, but it cannot keep an unheated greenhouse frost free through every Canadian winter night. Heat still escapes through glazing, frame, doors, vents and the ground perimeter. Cold-climate growing may require supplemental heat, insulation measures and temperature monitoring.
Thicker multiwall glazing can reduce heat loss, but it may cost more, weigh more or admit less light depending on the product. If winter heating is a priority, evaluate the whole enclosure and estimated heating needs, not just a millimetre figure.
What About Summer Light and Diffusion?
The channels scatter incoming light, which can make illumination more even around foliage than a perfectly clear panel. That does not eliminate overheating. A compact polycarbonate greenhouse can still get hot on sunny days; roof vents, a low intake and, when needed, a fan or seasonal shade should be planned together.
Compare published light-transmission figures for the actual panels. Colour, thickness, coatings and ageing may change how much useful light reaches plants.
How Important Is the UV-Protective Layer?
Ask whether the panel has a co-extruded UV-protective surface and which side faces outward. Follow the manufacturer's orientation markings during assembly. A protective layer and a clearly stated warranty can matter for long-term clarity and resistance to yellowing.
Keep the protective film on only as long as the panel instructions say. Once installed, check whether the exposed face is the specified UV side.
Why Do Channels Sometimes Collect Water or Dirt?
Open channel ends can admit dust, insects and moisture. Manufacturers may specify different tape or closure details for the top and bottom edges so the channels are protected while condensation can drain. Follow the supplied installation details and maintain the drainage paths; sealing every channel completely with improvised materials can trap moisture.
Some condensation in or on glazing does not by itself prove a panel is defective. Persistent dirty water, blocked drainage or poorly fitted edge closures deserve inspection.
Does Thicker PC Make the Whole Greenhouse Stronger?
A thicker panel does not automatically make a stronger greenhouse. Snow and wind loads pass through the glazing supports, connections, bracing, base and anchors. The spacing of the frame members and the method retaining each panel may matter as much as panel thickness.
Ask for documentation supporting any wind or snow rating for the exact kit and installation. A panel supplier's material data alone is not a load rating for the complete greenhouse.
What Should a Canadian Buyer Check?
- Verified panel construction, thickness and UV orientation.
- Light and thermal data for the actual glazing option.
- Panel edge closures and drainage instructions.
- Channels, strips or fasteners that hold panels against wind.
- Frame bracing, continuous base and suitable anchoring.
- Availability of replacement panels and their dimensions.
- Evidence for structural claims for the assembled model.
Final Thoughts
Six-millimetre twin-wall PC can be a reasonable glazing choice for a small backyard greenhouse, but whether it is enough depends on intended winter temperatures, local exposure and the complete kit design. Evaluate the panel alongside ventilation, frame, panel retention and anchoring before choosing a polycarbonate greenhouse in Canada.
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