September 11th

The Bailey guide to Rainscreen Systems

BBH 1223

While the primary reason for specifying a rainscreen cladding system may be down to the visual impact of a project, whether that is to improve the appearance of an older building or to drive the aesthetic of a new build, rainscreen systems are excellent for providing effective (low risk) solutions to a number of other criteria.

Correctly specified, a rainscreen cladding system will provide effective weather-proofing, contribute to the overall thermal performance of a building and guard against water, wind and fire.

In spite of its name, rainscreen cladding is designed to work with, rather than against, nature’s elements to protect the structure of a building from wind and rain. The durable properties and design versatility of rainscreen systems make them an effective solution to aesthetic and performance needs.

There are three main types of rainscreen cladding systems:

Vented Systems

Drained and Vented Systems

Pressure Equalised (Moderated) Systems

Each system is better suited to different applications so to find which is most appropriate for your project we’ve identified the key features of each system below:

Vented Systems

Although commonly known as ‘vented’, this system should really be called a ‘drained’ system as it doesn’t allow for ventilation.

Vented rainscreen systems are mainly used with a render. The system works using a warm cavity which provides a dew point close to the outside, ensuring a very low risk of moisture penetrating the system.

This type of rainscreen cladding shouldn’t be used on buildings more than 4 storeys high. The higher the rainscreen cladding system the greater the risk of water penetration and high wind loads. This could result in a build-up of condensation where an excessively high system is unable to dry out.

Key Features:

  • Cavity open at the bottom only
  • Provides drainage but no convective ventilation
  • Warm cavity, no ventilation

Drained and Vented Systems

This system works with a cold cavity structural build up. Due to the pressure exerted on the system by the wind, this system is best specified less than 12 meters in height.

As with the vented system, drained and vented systems should not be used on buildings more than 4 storeys high to prevent a build-up of condensation, which wouldn’t dry out and could lead to the removal of panels by high wind loads.

Key Features:

  • Not watertight
  • Cavity must be open at top and bottom
  • Cavity must provide drainage and promote convection ventilation
  • Protect cavity with overhang
  • Protect backing structure with moisture barrier (VCL)
  • Non-hygroscopic or closed cell insulation (PIR or Rockwool)
  • Excessively high D+V systems should be avoided

Pressure Equalised (Moderated) Systems

This rainscreen cladding system is cavity compartmentalised to control pressure and stop the spread of fire through the building.

This system allows wind to blow in and behind the rainscreen panels, equalising the pressure, resulting in a very low wind load on the panels themselves. The remaining wind load is transferred onto the structure. Designing in accordance to BS6399-2-1997 with correct wind loadings is critical.

This system is commonly used over 4 storeys (approx. 12m).

Key Features:

  • Cavities are compartmentalized
  • Openings calculated to allow rapid ingress and egress of air
  • Water ingress reduced by ‘equalization’ of internal and external pressures (pressure moderated system)
  • Drained above compartment levels
  • Suited to tall areas of rainscreen
  • Design intensive
  • High pressures generated at corners require that the centres of vertical compartments are reduced.

Our experts can help to advise which type of rainscreen cladding is suitable for your project.

To see examples of our rainscreen cladding, please visit our case studies page