A2 ACP vs Solid Aluminium vs Honeycomb: Which to Choose?
“Metal cladding” describes three products that behave nothing alike on a facade. A composite panel is two thin aluminium skins bonded to a core. A solid aluminium panel is one sheet of the same metal, thicker. A honeycomb panel is two skins bonded to an aluminium foil core built like a beehive. Every one of them is correctly called aluminium cladding, and each one forces a different sub-frame, a different fabrication method and a different fire argument.
The choice is usually made on weight, and that is the wrong first question. Weight sets the sub-frame, and the sub-frame is where the budget goes. This guide compares the three systems on the numbers that actually move a project, and on the two things that get decided after the panels are ordered and cannot be fixed later.
The three systems
| System | What it is | Typical build |
|---|---|---|
| ACP | Two aluminium skins bonded to a core — polyethylene, FR mineral-filled, or A2 mineral | 3–6 mm total, usually 0.5 mm skins |
| Solid aluminium | A single aluminium sheet, formed and returned at the edges | 2–4 mm |
| Honeycomb | Two skins bonded to an expanded aluminium honeycomb core | 6–25 mm total |
The sandwich is the whole point of the first and third. Bonding two skins to a core pushes the metal away from the neutral axis, which is why a 4 mm composite panel can be stiffer than a 4 mm solid sheet while weighing about half as much. A solid sheet has to earn its stiffness the expensive way: by being thicker, and by being folded into returns that a composite panel does not need.
Weight: the number that sets the sub-frame
| Panel | Approximate weight |
|---|---|
| 4 mm ACP, PE core | ~5.5 kg/m² |
| 4 mm ACP, A2 mineral core | ~7.5–8.0 kg/m² |
| 2 mm solid aluminium | ~5.4 kg/m² |
| 3 mm solid aluminium | ~8.1 kg/m² |
| 4 mm solid aluminium | ~10.8 kg/m² |
| 10 mm aluminium honeycomb | ~6–7 kg/m² |
Treat those as order-of-magnitude figures for comparison and take the supplier’s own data sheet for anything that goes into a structural calculation. Aluminium is about 2.7 g/cm³ whatever form it arrives in, so a solid sheet’s weight is simply its thickness times that density. The composite systems escape the arithmetic because most of their volume is not metal.
Two consequences follow. First, the heavier the panel, the heavier the rails, brackets and anchors behind it, and that cost is rarely in the panel quotation. Second — and this catches people — an A2 mineral core is considerably heavier than a PE core at the same thickness. The mineral filler that earns the fire class is dense. If a project moves from a PE panel to an A2 panel late, the facade weight goes up by roughly a third and the sub-frame may need redesigning. That is a conversation to have before the structural drawings are frozen, not after.
Stiffness and flatness
Flatness is what a client actually sees. All three systems can deliver it, but they pay for it differently.
- A2 ACP holds a flat face at standard panel sizes without stiffeners, which is why it dominates rainscreen and ventilated facade work. It is the easiest of the three to keep visually flat over a large elevation.
- Solid aluminium is the least stiff per kilogram. At 2–3 mm it needs returns on every edge and often stiffeners across the back of anything wider than about 600 mm, and those stiffeners have to be bonded or riveted on before coating if the finish is to stay clean.
- Honeycomb is the stiffest of the three for its weight and is the usual answer for very large single panels, deep reveals and long unsupported spans. It is also the least forgiving to cut.
Fire: where the three separate
| System | What is actually being classified |
|---|---|
| A2 ACP | The panel as a tested construction. A mineral core reaches A2-s1,d0 to EN 13501-1, or A2 to GB 8624. The classification covers the panel as tested — core, skins, adhesive and coating. |
| Solid aluminium | The metal itself is non-combustible and needs no classification. There is nothing to classify because there is no organic core. The coating, the fixings and the insulation behind it are separate items. |
| Honeycomb | The aluminium skins and core are non-combustible; the adhesive bonding them, and the edge closures and fixing inserts, are the variable. The finished assembly can perform to A2 or better, but it depends on materials chosen at manufacture. |
This is the section where a quotation comparison usually goes wrong. A solid aluminium panel is not “more fire-rated” than an A2 composite panel, because the sheet was never the part that could burn in the first place. What burns in either system is the coating, the adhesive, the insulation and the cavity behind. That is why the United States tests the whole wall assembly to NFPA 285 rather than the panel alone, and why a European classification report names the exact construction it was issued for.
If a specification names A2, a solid aluminium panel is not a compliant substitute simply because metal does not burn. Check what the code asks the assembly to do. What EN 13501-1 A2-s1,d0 actually means breaks the classification down, and PE vs FR vs A2 core covers the choice inside the composite family.
Cost: where the money actually goes
Per square metre of panel, solid aluminium is the more expensive sheet and honeycomb is the most expensive of the three; a composite panel is the cheapest. That ranking is real but it is rarely the ranking that decides the project, for three reasons.
- The sub-frame scales with weight. The heavier the panel, the more steel and more anchors behind it. On a tall elevation this can consume the difference in panel price.
- Fabrication is not the same job. A composite panel is routed and folded with hand tools on site, and a change of opening size is a morning’s work. Solid aluminium needs press-brake capacity, and honeycomb needs edge closures and inserts at every fixing point. Different labour, different shop, different lead time.
- A2 is priced by its core. Within composite panels, moving from PE to FR to A2 is a step change in cost, because the mineral content is the product. The skin thickness and the coating then move it again.
Comparing quotations on a single price per square metre is how projects get into trouble. The variables that actually set the number are set out in the price guide.
Which system for which project
- Large ventilated rainscreen facade, budget and programme both live: A2 ACP. Flat, light, quick to fabricate, and it reaches the fire class that high-rise codes ask for.
- Deep reveals, long unsupported spans, or a panel size nothing else can hold flat: honeycomb, accepted that fabrication is specialist and cost is highest.
- Small area, tight radius, or a design that wants the metal itself expressed with visible folded returns: solid aluminium, where the extra weight and stiffening are not a problem because the elevation is small.
- Anything above roughly 18 m, or any escape route: start from the fire clause in the code and work backwards. The classification and the test report decide the system, not the reverse.
Frequently asked questions
Is solid aluminium safer in a fire than A2 composite panel?
Not in the way the question implies. The aluminium sheet does not burn in either case. What burns is the coating, the adhesive, the cavity insulation and whatever is stored behind the facade, which is why codes test the whole assembly. An A2 composite panel carries a classification for the complete tested construction; a solid sheet simply has no combustible core to classify. Which one complies depends on what your code asks of the assembly.
How much heavier is an A2 panel than a PE panel?
At 4 mm, roughly a third heavier — about 7.5 to 8.0 kg/m² against about 5.5 kg/m². The mineral filler is what earns the fire class and it is dense. On a large facade that difference reaches the sub-frame, so confirm it while the structural design is still open.
Can a composite panel span as far as honeycomb?
No. Honeycomb is the stiffer system and holds larger single panels flat. Composite panel covers the great majority of rainscreen work at standard panel sizes without stiffeners; honeycomb is the answer when the design demands sizes or spans that composite panel cannot hold.
Does an A2 classification on one panel cover the whole facade?
No. The report names a specific construction — core type, panel thickness, coating system, and the assembly it was tested in. Change the thickness or the finish and the document no longer describes what you are buying. That is why the certificate has to be read against the order, not filed next to it.
About Jinxiang
Zhejiang Jinxiang Panel Industry Co., Ltd. manufactures aluminium composite panel and colour-coated aluminium coil in Jinhua, Zhejiang, with an annual capacity of 6 million square metres of composite panel and 8,000 tonnes of coated coil. The coil, the coating and the composite panel stay under one roof, and our dedicated A2 fire-rated line can produce panels up to 2,000 mm wide, which means fewer joints across an elevation. We export to more than 70 countries. MOQ is one standard container for stock colours, with a 500 sqm minimum per colour for custom colours, and lead time is 10–15 days after deposit.
Send us the elevation, the destination market and the fire clause you are working to, and we will tell you which system fits and quote the core and coating that satisfy it. See the A2 fireproof aluminium composite panel range, read the A2 sourcing guide, compare the full aluminium composite panel range, or contact us for a quote, a sample kit or a factory tour.