Rockwool Rainscreen Duo-Slab

A1 non-combustible insulation for ventilated façade & cladding systems

The Rockwool Rainscreen DUO SLAB is a non-combustible insulation slab manufactured for application within façade systems. Not only does the DUO SLAB provide A1 rated fire properties (in the correct system) but it also achieves a thermal conductivity of 0.034 W/mk, water vapour resistance of 5.9 MNs/gm and provides tested acoustic benefits.

*Always Refer Back To Manufacturers Specification Document*

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Effective non-combustible thermal and acoustic insulation for ventilated façades RAINSCREEN DUO SLAB is a dual-density insulation specifically developed for use within ventilated cladding systems, as well as sealed systems such as curtain walling.

Once installed, the robust outer surface of the slabs, in combination with a factoryapplied water repelling agent, acts to resist rain ingress during construction.


RAINSCREEN DUO SLAB is a dualdensity insulation, meaning that the outer layer of each slab is manufactured to a higher density than the remainder of the product.

This results in a robust outer surface designed to withstand the rigours imposed on site, and a  esilient inner face designed to accommodate any irregularities in the substrate.

A water-repelling agent is added to the product during manufacture, which in combination with a robust outer surface and random fibre orientation, prevents water transmission through the insulation layer. As such the slab is well-designed for use in conditions of severe climatic exposure.

The product can be easily fitted around brackets and other awkward details, and when tightly butt jointed the fibres of adjacent slabs will knit together to provide a continuous thermal performance – eliminating heat losses that could otherwise be caused by gaps and joints. Its unique dual density construction also means that RAINSCREEN DUO SLAB requires fewer fixings, making it a costeffective solution that is quick to install.


• Designed for use on high rise buildings.

• Water-repellent: Fibres impregnated with a waterrepelling agent during manufacture.

• Fewer fixings required for installation compared to standard stone wool slabs.

• Robust front face resists damage and over-driving of fixings.


RAINSCREEN DUO SLAB is designed for use within ventilated cladding systems, as well as sealed systems such as curtain walling.



Rated Euroclass A1 when assessed to EN 13501-1 using test data from reaction-to-fire tests. Wind resistance RAINSCREEN DUO SLAB fixed as indicated in Figure 1 has successfully undergone wind resistance testing by the Building Research Establishment.

Wind loading fatigue tests were used to simulate the performance of the slabs when fully exposed and subjected to fluctuating wind loads during the construction stages of buildings.

The tests simulated and exceeded the maximum UK basic wind speed of 56 m/s as defined by BS CP3: Chapter 5: Part 2: 1972. Test report reference BRE GI2801.

Water resistance

ROCKWOOL stone wool repels liquid water due to its fibre orientation and the presence of water repellent additives.

Acoustic performance

The airborne sound reduction of several typical rainscreen buildups incorporating RAINSCREEN DUO SLAB was tested at the Sound Research Laboratories (SRL), with results of up to Rw 62 dB.

For more information, please see the ‘Acoustic Performance of Rainscreen Façade Systems’ brochure available on our website.

Condensation control

The vapour resistivity of ROCKWOOL mineral wool is 5.9MNs/ gm. The slabs therefore reduce the risk of condensation, allowing natural drying-out of the structure. See typical relative humidity / temperature graph below.

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