A ventilated facade is not cladding stuck to a wall. It is a two-layer system where the outer panel sheds most water and the cavity behind it drains and dries whatever gets past. Understanding that distinction is what separates a facade that performs for twenty years from one that traps moisture against the structure.

The Principle

A rainscreen accepts that some water will penetrate joints. Rather than trying to make the outer skin perfectly sealed — which fails eventually — it provides a drained and ventilated cavity so that penetrating water runs down the cavity face and exits at the base, while airflow evaporates residual moisture.

The outer panel handles the bulk. The cavity handles the remainder. Neither works alone.

The Four Functions of the Cavity

1. Drainage

Water entering through joints must have an unobstructed path down and out. The cavity base must be open — screened against vermin, never sealed.

2. Ventilation

Air entering at the base and leaving at the top drives evaporation. Without this airflow, the cavity becomes a humid enclosed space rather than a drying one.

3. Thermal buffering

The cavity’s rising air carries away heat absorbed by the panel. This is why dark cladding is viable on a ventilated system and problematic on a direct-fixed one. On a hot Indian afternoon the difference in heat reaching the structural wall is substantial.

4. Pressure moderation

Equalising air pressure across the outer panel reduces the pressure differential that drives water through joints in the first place.

Cavity Design Requirements

  • Depth: typically 25 to 50mm; follow the system specification rather than a rule of thumb
  • Open at base: for drainage and air intake
  • Open at top: for air exhaust — a cavity open only at the base does not ventilate
  • Unobstructed: horizontal framework members should not dam the cavity; use spacers or notching
  • Clear of debris: the base must stay clear of leaves and construction waste

The Insulation Question

Insulation can be included, but it must sit against the structural wall with the ventilated cavity maintained outboard of it. Packing insulation into the cavity itself converts a drained rainscreen into a moisture trap. This is a common and costly error.

Fire Considerations

The same cavity that drains and ventilates can also allow fire to travel vertically. On multi-storey buildings, cavity barriers at floor levels and around openings are typically required. These interrupt vertical fire spread while still permitting drainage and limited airflow. This is system design, not a panel specification, and needs qualified input.

Framework Selection

The substructure sits permanently inside a humid cavity, so corrosion resistance matters more than on an exposed element. Aluminium is the durable choice for coastal, high-rise and long-life projects. Galvanised sections are a reasonable default for general work, with cut ends and drilled holes treated. Bare mild steel in a ventilated cavity in a humid climate is a short-term decision.

Frequently Asked Questions

What is a ventilated facade?

A cladding system with a drained and ventilated air cavity between the outer panel and the structural wall, allowing water to drain and moisture to evaporate.

How deep should the cavity be?

Typically 25 to 50mm, open at both base and top. Confirm against the specific system specification.

Can insulation go in the cavity?

Insulation should sit against the wall with the ventilated cavity maintained outboard of it. Filling the cavity itself prevents drainage and airflow.

Does a ventilated facade reduce cooling load?

It reduces heat transfer into the structural wall by carrying absorbed heat away in the cavity airflow. Actual savings depend on building design, orientation, insulation and climate, and should be modelled rather than assumed from a headline figure.

Designing a ventilated facade? Contact HPLMaker for system details, cavity guidance and framework specifications.