Rainscreen Façade System: Open State Cavity Barrier
A complete, tested rainscreen system, featuring open state cavity barriers with ventilated cavities and a cladded façade.
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Application Overview
In this application, a ventilated cavity has to be maintained between the rainscreen insulation and the external cladding to allow the construction to breathe and moisture collected within the cavity to escape. When positioned at compartment wall level, they sub-divide the building both vertically and horizontally into compartments. They are also used to close off penetrations such as windows and doors.
Products Used In An Open State Cavity
In open state cavity, Rocksilk® RainScreen OSCB should be specified for the horizontal barrier & Rocksilk® RainScreen FireStop Slab should be specified for the vertical barrier.
Meeting Specification Challenges With Rocksilk® RainScreen Slab
Common Rainscreen System Questions
Rocksilk® RainScreen Slab EE is manufactured with a water-repellent additive meaning they will not transmit water to the external wall structure. The physical and chemical characteristics of the fibres are unaltered by wetting. Therefore, the thermal properties of Rocksilk® RainScreen Slab EE are not affected by exposure to moisture and the product will perform as expected once dry and undamaged.
Yes. It is possible for Rocksilk® RainScreen Slab to be used both above and below 18 metres in height, when installed in accordance with Agrement Certificate from the BBA (19/5609 Product Sheets 1 and 2) and depending on the full wall build-up.
Fire resistance is the measurement of the ability of a material or system to resist, and ideally prevent, the passage of fire from one distinct area to another.
Reaction to fire is the measurement of how a material or system will contribute to the fire development and spread, particularly in the early stages of a fire when evacuation is crucial.
Insulation with a ‘Euroclass A2-s1,d0’ classification is considered non-combustible as set out in changes to the building regulations 2010 which bans the use of combustible materials, limiting use of materials to those achieving A1 or A2-s1,d0 on buildings in scope of the ban (as defined in regulation 7(4)).
There are different approved documents, technical handbooks and booklets that provide guidance on the building regulations. Here is a list of technical documentations to support Fire Strategy:
- Approved Document B in England
- Approved Document B in Wales
- Technical handbooks in Scotland
- Technical Booklet E in Northern Ireland
- Technical Guidance Documents in Republic of Ireland
Knauf products are rigorously tested and certified to meet regulations outlined by the Building Safety Act (2022), ensuring our products meet the required standards. We are transparent with our technical documentation and certification which include fire, acoustic, and structural performance data. This information is available via our Download Centre or on NBS Source. We also offer RIBA-accredited CPDs to help architects and specifiers stay updated on regulatory changes.
Please start by trying our online U-value calculator. It has a 3D U-Value calculator built in, enabling you to obtain accurate U-values for rainscreen cladding systems.
Alternatively, you can email your build-up (section drawing) to our Technical Services Team at technical.uk@knaufinsulation.com.
We offer expert advice on all our insulation products and solutions through our in-house Technical Services Team (TST). With over 20 years’ insulation experience, our TST provide free, expert advice to construction professionals. Get in touch here.
The help desk is operated from 8.00am to 5.00pm Monday to Thursday and 8.00am - 4.00pm Friday, by experienced insulation experts, ready to provide advice on regulations, products, and energy performance.
Our BBA accredited Knauf ThroughWall is a one-brand solution that provides the integral parts of a non-loadbearing infill exterior wall system. It is designed to meet required building performance while allowing the flexibility of external finishes to be applied, such as cladding boards and brick slips (supplied by others). ThroughWall can also be used for buildings of 18 metres and over.
Knauf ThroughWall is made up of Knauf Plasterboards, Knauf Steel Framing Solutions, Knauf Insulation OmniFit® Slab 35, Knauf Windliner and Knauf Insulation Rocksilk® RainScreen Slab.
Our products can be used to earn points under multiple criteria in green building rating schemes, including those related to energy efficiency, embodied carbon and responsible sourcing.
We have produced help sheets to show which credits our products can contribute towards. You can download these from our Download Centre.
Other Rocksilk® RainScreen Cavity Systems
Knauf Insulation Rocksilk® RainScreen Slab is designed for use in a variety of systems and wall build-ups.
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