In terms of protecting a building, a properly constructed rainscreen build-out is one of the most reliable and highest performance options in today’s market.
How so, you may ask?
Well, a rainscreen protects and extends the life of a weather-resistive barrier (build-out) and provides other key benefits as described below:
- Weatherproofing (rapid pressure equalisation and layers of redundancy)
- Exceptional thermal rating and performance
- High airflow within the cavity, allowing moisture drainage and evaporation
- Low maintenance – dry system with no seals/caulking maintenance
- Long life expectancy
- Flexible design thanks to many profile options within the current market
When designing a rainscreen, it is critical that you understand the fundamentals and the role of each component. There is a chance you might find it tough to ensure it will be effective at protecting a building, but not to worry. Within this blog, we’ll be explaining the most common types of rainscreen, the components and how they go together.
We hope this resource helps you in creating your future facade designs!
First things first…
Here’s a quick refresher on what a rainscreen actually is. A rainscreen facade is a two-stage construction:
- Inner wall: A load-bearing insulated wall that is protected by an outer surface.
- Outer surface: Protects against rain and moisture and provides a cavity between the cladding and building wall to prevent water from infiltrating the building structure.
Types of rainscreens
Three types of rainscreen systems effectively protect a building using an external layer and an airflow/ evaporation barrier.
These include:
- Drained and back ventilated rainscreen
- Vented rainscreen
- Pressure equalised rainscreen
Drained and back ventilated rainscreen
This is designed to drain off most of the rainwater via the outer surface. The joints are designed to protect against the kinetic energy of wind-driven rain, achieved by adding baffles or limiting joint width. The cladding is allowed to leak and the cavity behind the cladding is drained by positive back ventilation, which promotes rapid evaporation of any rainwater deposited on the inner leaf.
Vented rainscreen
Vented systems are only open at the bottom, with the primary focus being to drain moisture. These are mainly used with face-sealed cladding systems, aiming to deal with condensation and potential long-term system failure
Pressure equalised rainscreen
Pressure-equalised (PE) rainscreen cladding systems allow the movement of air between the inside and outside of the rainscreen. This equalises the pressure across the rainscreen so that water is not driven, or engulfed through the joints.
For the purpose of this blog, we’ll be expanding on the drained and vented type of rainscreen.
Components of a rainscreen
There are six main components in the build of a rainscreen. They are installed in the following order:
- Existing structural wall
- Stud/nogging
- Insulation
- Weather protection membrane
- Air cavity
- Cladding
How do these components go together?
The first part is the existing building structure, which provides a strong wall in which to build the rainscreen out from. Rainscreens can be applied to any building structure as they are designed to add extra building protection.
The second component is the stud or nogging, which is basically a framework to attach the rest of the rainscreen components to, and is usually made from steel or timber.
Then comes the insulation. Materials used for insulation usually include mineral wool batts, foam sheathing or closed-cell spray foam. This insulation helps keep a building cool in summer and warm in winter.
A weather protection membrane is then applied to protect the insulation and keep the weather out. It should cover the whole building. This seals the building and is a second line of defence against water ingress (leaky building syndrome). An essential part of this step is to ensure that there are no gaps for moisture to infiltrate. Tape is used to piece the material together into one big envelope.
After the insulation and membrane are installed, an air cavity is created between the membrane and the cladding, allowing for continuous drainage and ventilation. This helps to protect the building and increase thermal qualities.
Cladding is the final part of the build-out. It is the first layer of protection, taking the brunt of harsh weather and blocking most moisture from moving past it. Cladding also provides immense aesthetic qualities, helping to both protect a building and appear attractive – with many profiles available within the market.
Each component of the build-out has a very specific purpose. This is where the engineering of the system shows its major benefits.
Key considerations
There are five areas to consider when designing a quality rainscreen build-out:
- Thermal performance
- Weatherproofing (watertight and airtight)
- Fire compliance
- Wind loads, spans and connection capacities
- Appearance
Velo Facades
Sustainable building practices and regulatory compliance are paramount in the construction landscape. With advancements to enhance thermal performance, mitigate condensation risks and reduce water leaks, the industry is ripe for innovative solutions that not only meet, but exceed these evolving standards.
Introducing Velo Facades, a high-performance envelope solution featuring Sculptform’s signature concealed fixing aluminium rainscreen cladding.
