Rockwool RWA45 Acoustic Insulation Slab
(10 Products)RWA45 is the “fit-and-forget” choice for builders who need reliable soundproofing plus built-in fire protection, without complicated installation steps or special fixings.
Engineered from high-density (45 kg/m³) stone-wool slabs, it friction-fits between studs, joists or rafters and stays exactly where you put it, no sagging, slipping or stapling, so you can close up and move on with total peace of mind.
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What is Rockwool RWA45?
RWA45 is part of the extensive Rockwool slab product range. The "RWA" stands for Rockwool Acoustic, indicating its primary focus on sound performance, while the "45" denotes its nominal density of 45 kg/m³.
This density is key to its multi-functional capabilities. It is manufactured from volcanic rock (basalt) and recycled slag, melted at high temperatures and spun into fine, non-combustible fibres, which are then formed into slabs.
Applications
- Internal Partition Walls: Ideal for reducing sound transmission between rooms in residential, commercial, or public buildings
- Separating Floors: Used between floor joists to reduce airborne and impact noise transfer between different levels of a building.
- Suspended Ceilings: Placed within ceiling voids to absorb sound, improve room acoustics, and reduce noise from above.
- External Timber and Steel Frame Walls: Provides effective thermal, acoustic, and fire insulation within the framed cavities of external wall constructions.
- Pitched Roofs (Between Rafters): Used to insulate habitable loft spaces or rooms in the roof, contributing to thermal comfort and sound reduction from external elements.
Benefits
- Acoustic Absorption: RWA45's high-density and non-directional fibre structure make it highly effective at absorbing sound waves. This significantly reduces airborne noise transmission (e.g., voices, music) and helps control reverberation (echo) within spaces.
- Thermal Insulation: The fibrous composition traps air, providing a thermal conductivity (lambda value) of 0.035 W/mK. This low conductivity ensures effective resistance to heat flow, helping to maintain stable indoor temperatures and reduce energy consumption for heating and cooling.
- Outstanding Fire Performance: As a stone wool product, RWA45 is inherently non-combustible. It achieves the highest Euroclass A1 reaction to fire classification (to BS EN 13501-1). This means it will not contribute to the development or spread of fire and has a melting point exceeding 1000∘C, acting as a critical fire barrier within constructions.
- Water Repellent: RWA45 slabs are treated to be water repellent, resisting the absorption of liquid water. This property helps to prevent issues like dampness, mould, and rot.
- Dimensional Stability: The slabs are robust and dimensionally stable, meaning they retain their shape and thickness over time without slumping or shrinking. This ensures that the thermal and acoustic performance remains consistent throughout the building's lifespan.
- Easy to Install: Their semi-rigid nature allows for simple friction-fitting between standard timber or metal studwork, reducing installation time and the need for additional fixings in many applications. They can be easily cut to size with a sharp knife.
Performance Properties
RWA45 offers a single-product answer to stringent acoustic, fire-safety, thermal, and sustainability requirements, making it a versatile choice across multiple building disciplines.
Acoustic Performance
- 45 kg/m³ density and open-fibre structure absorb airborne sound across speech and traffic frequencies.
- When installed in constructions tested by ROCKWOOL (see datasheet), partitions comfortably meet Approved Document E or Section 5 (Scotland) acoustic targets.
Fire Performance
- Euroclass A1 rating. Fibres remain intact above 1000°C; product is non-combustible and gives off negligible smoke.
- Maintains integrity of fire-compartment lines in multi-storey residential and commercial projects.
Thermal Contribution
- 0.035 W/m·K; assisting compliance with Part L fabric U-values.
Moisture Behaviour
- Fibres are water-repellent yet vapour-permeable, allowing assemblies to dry and limiting mould risk in basements, bathrooms, and ventilated facades.
Sustainability
- Manufactured from abundant volcanic rock and up to 40% recycled content.
- Fully recyclable via Rockwool take-back schemes; third-party EPD available (EN 15804).
Frequently Asked Rockwool RWA45 Slab Questions
What Does RWA45 Mean?
RWA45 is the name that Rockwool gives to their most popular acoustic insulation slab.
The RW stands for “Rockwool”, A stands for “Acoustic” and the 45 refers to the fact that these slabs have a density of 45kg/m3 and 0.035 W/mK thermal conductivity.
You will see that there is more than one product on our site labelled RWA45. All slabs are essentially the same product, just with varying thicknesses.
Our 25mm Rockwool RWA45 acoustic sound insulation slab (16 slabs per pack) is the same as our 100mm Rockwool RWA45 acoustic sound insulation slab (4 slabs per pack), only it is not as thick and, therefore, will not provide the same level of soundproofing.
You can read more about these materials on the Rockwool RWA45 data sheets, which are available under ‘Technical Downloads’ on each product page.
Are Rockwool RWA45 Slabs Flammable?
Rockwool RWA45 slabs are classed A1 on the Euroclass scale, which means they achieve the highest rating for non-combustibility and fire performance, and are completely non-flammable.
If you were to hold a blowtorch next to a piece of Rockwool RWA45, it might begin to glow but it will not catch fire or melt.
Lloyd’s register of shipping has also certified RWA45 slabs as approved non-combustible materials for fixed offshore installations and MED classed ships.
How Should I Cut Rockwool RWA45 Acoustic Insulation Slabs?
We recommend marking the measurements you need on the slab before cutting. You can use a utility knife or even a serrated knife to cut Rockwool slabs.
As always, we encourage our customers to take proper safety precautions during any general building projects.
You should always use safety goggles and even gloves when cutting materials. We also advise cutting the slabs in a large, clear space with appropriate ventilation.
What Are Rockwool RWA45 Acoustic Insulation Slabs Made From?
The production process for Rockwool essentially emulates the inside of a volcano that spins and cools lava in a controlled environment. Rockwool is created by spinning molten rock and minerals with steel slag to create a cotton-candy-like wool product.
Who Are Rockwool?
Rockwool is a industry favourite manufacturer of stone wool insulation. With over 80 years of experience manufacturing stone wool products, they are trusted experts in their field.
They introduced their first thermal acoustic and fire insulation solution to the market in 1962.
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