Twin-wall and multi-wall polycarbonate comes in many thicknesses and can be bought in sheets or cut to the sizes you actually need. Here is a quick guide as to what to consider in making a choice for your project.
What Is Twin-wall and Multi-wall Polycarbonate
Multiwall polycarbonate is a polycarbonate with many walls or layers. Where the polycarbonate has two layers it is known as Twinwall Polycarbonate and where it has three or more layers it is known as Multiwall Polycarbonate.
Why Choose Twin-wall and Multi-wall Polycarbonate
It is this layering combined with its weight (very light) and strength (it is virtually unbreakable) which makes this type of polycarbonate popular. The more layers the polycarbonate has, the more insulation it provides. The material is often chosen because of its insulation properties. For someone taking on a roofing project, the fact that installation can be likely done single handedly because it is so light and easy to handle is another attraction.
The other draw to this type of polycarbonate is the UV protection it offers along with its ability (via its layers) to diffuse light and therefore give a more even distribution of that light and heat. For these reasons, twinwall and multiwall polycarbonate is a popular choice for greenhouses, conservatories and roofing.
This proven way of reducing the intensity of the light reaching inside the rooms / greenhouse means there is also a reduction in hot and cool patches too. Research has shown that evenly distributed light can help improve crop yield and leaf count as well as preventing plant injury such as leaf burn.
Choosing The Right Thickness For A Project
Twin-wall polycarbonate and multi-wall polycarbonate have the same properties but offer different levels of insulation. The easy way to remember it is the more layers there are, the greater the level of insulation provided by the polycarbonate. Because of this, the more layers the higher the cost too. It is important to consider how much insulation you need as the thicker multi-wall polycarbonate may be unnecessary or very necessary depending on how much additional heating may be required through longer, colder winter seasons if single layer glazing or thinner twin-wall polycarbonate is used.
Twinwall polycarbonate comes in sizes upto 10mm thick and lets in upto 80% – 83% of visible light.
All twin-wall sizes are suitable for greenhouse glazing and cold frames and the size to choose will depend on the level of thermal insulation (referred to as U-value) and light transmission you want.
A key consideration is every increase in thermal insulation comes with a trade off in light transmission. For example, choosing 16mm instead of 10mm means an increase in thermal insulation of 30% but a 9% reduction in light.
6mm twin-wall polycarbonate has a U-value of 3.5. Very strong and flexible, this size is suitable to replace single glass panes. Light transmission is 81%
10mm twin-wall polycarbonate has a U-value of 3, (note : this is double that of single pane glass. ) light transmission is 81%. This is suitable for skylights in warm climates.
Sizes 16mm thick onwards are known as Multi-wall polycarbonate and lets in circa 62% of visible light.
16mm multiwall polycarbonate has a U-value of 2.3 and light transmission 74%. This size is suitable for car ports and also greenhouses / skylights in colder climates where greater insulation is required.
25mm multiwall polycarbonate has a U-value of 1.7 and light transmission is 62%. This size is suitable for patio covers and pergolas where an open look is sought and high loads may be likely.
35mm multiwall polycarbonate has an U-value of 1.3 and light transmission 51%. This size is suitable for conservatories.