Twin Wall vs Triple Wall Polycarbonate: Which One Fits Your Project

People usually arrive at this question the same way: they have seen 8 mm twin wall and 16 mm triple wall side by side, the triple wall costs more, and they assume more must be better. Sometimes it is. Usually it is not.

What the difference actually is

Twin wall has two skins with ribs between them, so one layer of air. Triple wall adds a third skin and a second air layer. The air is what insulates, not the plastic, which is why a thicker panel with more chambers holds heat better.

It also loses a little light with every layer it adds, and it costs more per square foot.

8 mm twin wall

The all-rounder, and what we stock. It passes 76% of the light in clear, spans 2 to 3 ft between rafters, weighs about 10 lb for a 4x8 sheet and comes in at roughly R-1.74, where single pane glass is R-0.9.

That covers nearly every backyard job: greenhouses, pergolas, patio covers and carports, deck roofs, shed skylights. It also cold bends to a 55 in radius, so an arch is possible without heat.

16 mm triple wall

Worth the money in a narrow set of cases: a heated greenhouse you run through winter, a space you are trying to keep warm rather than just dry, or a roof carrying serious snow load.

The trade is real though. It costs noticeably more, it is heavier, so the frame has to be built for it, and it passes less light. In a Pacific Northwest backyard, where the problem is usually rain and grey skies rather than deep cold, paying for insulation often means paying to lose the light you were after.

So which one

If the structure is unheated, and that covers almost every pergola, patio cover, carport and hobby greenhouse around Seattle, 8 mm twin wall is the right panel and the cheaper one. If you are heating the space through winter and the heating bill matters more than the brightness, triple wall earns its price.

That is why we stock one line and stock it properly: 8 mm twin wall in clear, bronze and opal, in 4x8 through 4x20 ft, with the profiles and tape and screws that go with them.

Working out what your job needs

The buyer's guide goes project by project and counts the sheets and profiles for you. Light transmission, R-value, snow and wind loads and the minimum bend radius are on the technical data page, and fitting is covered in the installation manual.

Still not sure? Send us the width and depth of what you are covering and what it is for. Same day you get back a sheet count, a profile count and the delivery price for your ZIP. Call or text (702) 351-2441.

What we stock, and what it fits

One line, done properly: 8 mm twin wall polycarbonate in clear at 76% light transmission, bronze at 25% and opal at 44% diffused, in 4x8 through 4x20 ft.

Bronze for a pergola, patio cover or carport, where the point is shade. Clear or opal for a greenhouse, where the point is light. The seams close with H or snap profiles, and the edges with tape, screws and sealing bars.

Which panel your own job takes, and how many, is worked out project by project in the buyer's guide. If you are weighing twin wall against thicker multiwall, that comparison is in twin wall vs triple wall. Loads, spans and bend limits are on the technical data page, and fitting is in the installation manual.