Multiwall sheets for greenhouses – Which sheet is suitable when?

Greenhouses create a controlled microclimate that protects plants from the effects of the weather and promotes growth. For this interplay of light, warmth and protection to work optimally, the material used for the covering plays a central role. Multiwall sheets for greenhouses have proven to be particularly versatile, robust and efficient in this context.

Thanks to their insulating hollow-chamber structure, high light transmission and weather resistance, they are suitable both for simple lean-to greenhouses and for professional installations. But which sheet is really suitable for which requirements? This article clarifies exactly that in comprehensive detail.

What are multiwall sheets?

Multiwall sheets are plastic sheets with a multiwall construction in which so-called "webs" run between the outer layers. These hollow chambers offer several advantages at once: they reduce the weight of the sheet, improve thermal insulation and increase mechanical strength.

As a result, multiwall sheets are particularly resistant to wind loads and mechanical impacts, for example from hail or snow load. They let light through but at the same time scatter it slightly, which leads to more even illumination inside the greenhouse. This makes them a popular choice for greenhouses of all kinds, from small hobby installations to professional growing operations.

Advantages of multiwall sheets in the greenhouse

• Good thermal insulation thanks to hollow chambers
• Break resistance compared with glass
• Low weight makes installation easier
• UV protection with a suitable coating
• Variety of thicknesses and light transmission

Which materials are available?

Multiwall sheets are made from various plastics, whose properties sometimes differ considerably. The choice of the right material influences not only the light behaviour but also ageing resistance, temperature tolerance and maintenance effort. Three materials have become established for use in greenhouses:

Polycarbonate (PC)

• Very high impact strength, virtually unbreakable
• Good thermal insulation thanks to multiwall construction
• UV-resistant with a suitable coating
• High light transmission with simultaneous glare protection
• Temperature resistance from -40 to +120 °C
• Very durable and versatile, ideal for year-round use

Acrylic glass (PMMA)

• Excellent optical clarity, light transmission up to 92 %
• Naturally high UV resistance, no yellowing
• More scratch-resistant than polycarbonate
• Somewhat more brittle and less impact-resistant
• Particularly suitable for light-sensitive plants and demanding applications

PETG

• Inexpensive alternative to PC and PMMA
• Good transparency, easy to process
• Limited UV resistance
• Lower service life and mechanical load capacity
• Ideal for seasonal or short-term applications

Light transmission and UV protection

Light is the basis of life for every plant. The light transmission of a multiwall sheet directly influences the photosynthesis performance in the greenhouse. At the same time, excessively strong UV radiation can have a damaging effect. The right compromise between brightness and protection is therefore crucial.

Polycarbonate sheets generally have a UV protection layer on one or both sides, which prevents the sheets from becoming brittle or yellowing. This contributes considerably to the service life of the sheets and ensures that plants do not suffer from UV stress. Acrylic glass already offers natural UV protection thanks to its material structure, which is an advantage particularly for sensitive plants. PETG, by contrast, is only conditionally UV-stable, which is why it is more suitable for temporary constructions.

Depending on the type of plant, it may be sensible to choose sheets with a different degree of light transmission. While light-intensive crops such as tomatoes need plenty of direct light, shade-loving plants such as lettuce benefit from slightly scattered light. Specially structured or coloured multiwall sheets offer additional design options here.

Which thickness is the right one?

Depending on the place of use and the type of greenhouse, the requirements for sheet thickness vary. Here is a rough guide:

Sheet thickness	Application
4–6 mm	Cold frames, small hobby greenhouses
8–10 mm	Ordinary home garden greenhouses
16 mm	Winter-proof or heated greenhouses

Note: Thicker sheets offer better insulation but are more expensive and heavier.

Which sheet is suitable when?

For hobby gardeners

Polycarbonate sheets with a thickness of 6–8 mm offer good value for money and sufficient protection for cold frames or smaller greenhouses.

For year-round use

16 mm polycarbonate with UV protection on both sides is recommended here. The insulating properties help to reduce heating costs.

For light-intensive crops

Acrylic multiwall sheets are particularly light-transmissive and ideal for plants that need plenty of sun, e.g. tomatoes or orchids.

For budget projects

PETG can be an alternative if the greenhouse is used only seasonally and durability is of secondary importance.

In conclusion

Multiwall sheets for greenhouses offer many advantages: they are sturdy, insulating and light-transmissive. Which sheet is best suited depends on the specific application. Polycarbonate is the all-rounder, acrylic the premium solution for maximum light yield, PETG the inexpensive alternative for simple projects. Anyone wanting long-lasting results should pay attention to UV resistance and suitable sheet thicknesses.

FAQ on multiwall sheets in greenhouse construction

What service life do multiwall sheets have? High-quality polycarbonate sheets with UV protection often last 10 to 15 years. Acrylic can last even longer, PETG usually only a few years.

Can you cut multiwall sheets yourself? Yes, a precisely fitting cut is possible with a fine-toothed saw. Sharp edges should be deburred.

How do you clean multiwall sheets? Best with clear water and a soft cloth. Do not use abrasive agents in order to avoid scratches.

Are all multiwall sheets UV-resistant? No, only those with a suitable coating (usually polycarbonate) or made from UV-stable material (e.g. acrylic).