The flat, crisp metal panels on so many modern facades are composite panels — two thin metal skins over a core — and how their joints, attachment, and core are handled decides whether they perform or become a water and fire problem.
Metal composite material (MCM), often called aluminum composite material (ACM), gives modern facades their flat, precise metal look. Each panel is two thin metal skins bonded to a core, fabricated into cassettes and hung on a facade. The system performs well when its joints, attachment, and core are handled correctly — and becomes a water-intrusion or fire concern when they are not. The joint type, the rainscreen and attachment design, and above all the combustibility of the core are the decisions that determine whether a composite panel facade is done right.
The value is in the system, not just the panel. The sections below cover the four aspects that matter most — how composite panels are made, wet-joint and dry-joint systems, rainscreen and attachment, and fire performance and cores — and how ACE approaches composite panel systems.
These challenges rarely stay in one silo: the same discipline runs through lessons from air barrier types, our guidance on rigid insulation types, and what we have learned from sealant types and chemistry, and it all ladders up to ACE’s broader new-construction envelope design.
How composite panels are made explains much of their behavior, because a metal composite panel is two thin metal skins — usually aluminum — bonded to a central core, then routed and folded into cassettes with returned edges for attachment. Understanding that it is a skin-core-skin sandwich, fabricated into panels, is the starting point for the system.
The thin skins give the flat, rigid appearance, while the core provides stiffness and much of the panel’s fire and weight characteristics, so the core is not incidental but central to how the panel performs.
Because the panels are fabricated into cassettes with folded edges, their attachment and joints are designed around that cassette form, which leads directly into how the system is assembled on the facade.
Representative of the composite panel factors ACE reviews on facade projects. Illustrative distribution, not a published statistic.
Wet-joint and dry-joint systems are the two main ways composite panels handle the gaps between panels, because a wet-joint system seals the joints between panels with sealant, relying on that sealant as the weather line, while a dry-joint system leaves open or gasketed joints and manages water behind the panels as a rainscreen. The joint approach defines how the facade keeps water out.
A wet-joint system depends on the sealant remaining intact, which ties its long-term performance to sealant maintenance, whereas a dry-joint rainscreen accepts some water past the face and drains it behind the panels.
Because the two approaches manage water fundamentally differently, choosing and detailing the joint system correctly — and maintaining sealant where wet joints are used — is central to the facade’s water performance.
A composite panel facade is treated as just panels, with an untested core, poorly detailed joints, and weak attachment, becoming a water and fire risk.
Design the whole system: an appropriate fire-rated core, the correct wet- or dry-joint approach, a drained rainscreen cavity, and engineered attachment.
The facade sheds and drains water, carries its wind load, and meets fire requirements, so the composite panels perform as a safe, durable system.
Rainscreen and attachment tie the system to the building, because composite panels are commonly hung as a rainscreen on a support framework over a drainage cavity and the wall’s water and air barrier, and the attachment has to carry wind load while the cavity drains. Sound attachment and a functioning drainage cavity are what make the rainscreen work.
The panels themselves are not the weather barrier in a rainscreen; the barrier is on the wall behind, and the panels shed most water while the cavity drains what gets past, so the wall behind the panels matters as much as the panels.
Because the attachment carries wind load and the cavity manages water, both have to be engineered and detailed correctly for the composite panel system to perform structurally and keep water out.
Get the core, joints, rainscreen, and attachment reviewed so the ACM system performs and meets fire requirements.
Schedule a consultationCall (866) 389-8883Fire performance and cores are the most consequential composite panel decision, because the panel core can range from combustible polyethylene to fire-retardant and non-combustible mineral cores, and core combustibility has been central to serious facade fires. Selecting an appropriate core and meeting the applicable fire-testing requirements is essential.
Full-scale fire test standards for exterior wall assemblies exist precisely because a facade’s fire behavior depends on the whole assembly, including the core, and this has driven a shift toward fire-retardant and non-combustible cores.
The most valuable point overall is that a metal composite panel facade is a system — skins, core, joints, rainscreen, and attachment — and getting the joint type, the drainage, the attachment, and above all the core and its fire performance right is what makes ACM cladding safe and durable rather than a liability.
In ACE’s field work, most metal composite panel systems problems trace back to a few recurring locations — Core & fire performance, Joint system & water, and Rainscreen & drainage — rather than the open field of the wall or roof. The cost of resolving them climbs by roughly an order of magnitude at each stage: a detail corrected during design costs a fraction of the same fix during construction, which is itself far cheaper than a repair once the facility is operating. That economics is why we push envelope decisions as early in the project as possible.
Select an appropriate fire-rated core, the correct wet- or dry-joint approach, a drained rainscreen cavity, and engineered attachment for the wind load.
Confirm the core and the full wall assembly meet the applicable fire-testing requirements for exterior walls.
Confirm the joint type, drainage cavity, and attachment are installed as designed, and that the wall's barrier behind the panels is continuous.
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