Knauf Insulation Rocksilk® Rainscreen slabs
- BBA Certified (certificate 19/5609) for use in multiple build-ups so it can be specified with confidence.
- BBA Accredited 3D U-value calculation service - the most accurate calculation available.
- Made with a water-repellent additive - slabs will maintain their integrity while exposed on site.
Knauf Insulation Rocksilk® Rainscreen Slabs
- Non-combustible with a Euroclass A1 reaction to fire rating
- A+ Generic BRE Green Guide rating
Products
Rocksilk® RainScreen Slab is a BBA certified Rock Mineral Wool slab designed for use as sheathing insulation in rainscreen façade systems both below and above 18m in height.
It is non-combustible with the best possible Euroclass A1 reaction to fire classification, and is manufactured using Knauf Insulation's unique bio-based binder, ECOSE® Technology.
Application Overview
Mineral Wool rolls or slabs are friction-fitted between timber studs with additional non-combustible insulation partially filling the external cavity to further enhance thermal performance.
The reaction to fire classification of insulation products is an important consideration in order to minimise the chance of fire spread through the cavity. In addition, the reduced mass of timber frame walls means that insulation materials need to provide a higher level of acoustic performance to compensate
Our non-combustible solutions for timber frame buildings are designed to friction fit between studs to minimise heat loss, whilst also providing acoustic absorption to enhance the overall acoustic performance of the wall.
Typical construction
Inner leaf comprising 12.5mm plasterboard, vapour control layer, Knauf Insulation FrameTherm® Rolls between studwork, plywood sheathing, vapour permeable membrane and Knauf Insulation Rocksilk® RainScreen Slab. A 50mm cavity separates the insulation from the outer leaf, typically of brick or block
Installation
Knauf Insulation FrameTherm® Rolls are dimensioned to suit 90mm or 140mm studs at standard 600mm centres. The nominal thickness of the insulation should not be greater than the nominal stud depth.
Knauf Insulation FrameTherm® Rolls are friction fitted between studs at standard centres and are self-supporting. Generally, two slabs fully fill the space between sole and head plates for standard floor to ceiling height.
Rocksilk® RainScreen Slab can be installed using either brick tie channel or retaining discs. More information can be found in our Rocksilk® RainScreen behind masonry installation guide, found here.
A vapour control layer is stapled to the studs across the inner face of the wall before fixing the plasterboard. The vapour control layer should be free from holes, any gaps should be made good with any tears repaired and overlaps and apertures for services effectively sealed. Particular care is necessary around electric sockets and boxes.
A vapour permeable membrane or low emissivity vapour permeable membrane should be stapled or nailed to the sheathing board in accordance with the manufacturer’s instructions. It should be lapped so that each joint is protected, with upper layers lapped over lower layers to shed water away from the sheathing board.
Generally, horizontal laps should be at least 100mm wide and the membrane should extend below the lowest timber member. Vertical laps should be at least 150mm and be staggered.
Thermal performance
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Rocksilk® RainScreen Slab – 0.034 W/mK.
Reaction to Fire performance
Rocksilk® RainScreen Slab is classified as Euroclass A1 to BS EN 13501-1 which means that the product does not contribute to the development of a fire or flame spread Please contact Knauf Insulation Technical Support Team for U-value calculations that include specific products.
TYPICAL U-VALUES
FOR PARTIALLY FILLED MASONRY CAVITIES USING ROCKSILK® RAINSCREEN SLAB
102.5mm Brick outer leaf or 100mm Dense block and render with FramTherm® Roll/Slab 32
| U-value (W/m2K) | ||
| Rocksilk® RainScreen Slab (mm) | 90mm | 140mm |
| 250 | 0.10 | 0.09 |
| 210 | 0.11 | 0.10 |
| 200 | 0.11 | 0.10 |
| 180 | 0.12 | 0.11 |
| 150 | 0.14 | 0.12 |
| 120 | 0.16 | 0.13 |
| 100 | 0.17 | 0.14 |
| 75 | 0.20 | 0.16 |
| 50 | 0.23 | 0.18 |
Notes: Default timber fraction BR443:2019. Timber studs fully filled with FrameTherm® Roll or Slab 32 (0.032W/mK). 9mm sheathing and 2x15mm Standard wallboard internal finish. Rocksilk® Rainscreen Slab (0.034W/mK) installed with 50mm residual cavity using ACS 25/15 Framefix restraint system secured with stainless steel fixings. The above values are for guidance only, please contact our Technical Support Team direct for specific values.
FOR PARTIALLY FILLED MASONRY CAVITIES USING ROCKSILK® RAINSCREEN SLAB
102.5mm Brick outer leaf or 100mm Dense block and render with OmniFit® Slab 35
| U-value (W/m2K) | |||||
| Rocksilk® RainScreen Slab (mm) | 90mm | 100mm | 140mm | 150mm | 200mm |
| 250 | 0.10 | 0.10 | 0.09 | 0.09 | 0.08 |
| 210 | 0.11 | 0.11 | 0.10 | 0.10 | 0.09 |
| 200 | 0.12 | 0.11 | 0.10 | 0.10 | 0.09 |
| 180 | 0.12 | 0.12 | 0.11 | 0.11 | 0.10 |
| 150 | 0.14 | 0.14 | 0.12 | 0.12 | 0.10 |
| 120 | 0.16 | 0.15 | 0.14 | 0.13 | 0.12 |
| 100 | 0.18 | 0.17 | 0.15 | 0.14 | 0.13 |
| 75 | 0.20 | 0.19 | 0.17 | 0.16 | 0.14 |
| 50 | 0.24 | 0.23 | 0.19 | 0.18 | 0.15 |
Notes: Default timber fraction BR443:2019. Timber studs fully filled with OmniFit® Slab 35 (0.035W/mK). 9mm sheathing and 2x15mm Standard wallboard internal finish. Rocksilk® Rainscreen Slab (0.034W/mK) installed with 50mm residual cavity using ACS 25/15 Framefix restraint system secured with stainless steel fixings.
The above values are for guidance only, please contact our Technical Support Team direct for specific values