Sisalwool Acoustic Performance

Insulation is often considered primarily in terms of thermal efficiency, but acoustic performance is also important in creating comfortable and functional spaces. Effective sound control can reduce noise between rooms, limit intrusion from external sources, and enhance privacy and wellbeing within a building. 

Natural fibres such as sisal and wool offer a combination of sound absorption and dampening. The physical structure can help reduce echoes inside rooms and limit the transfer of noise between spaces, supporting calmer and more comfortable interiors. 

Sound absorption vs sound dampening 

Why Acoustic Insulation Matters 

Typical Applications in Buildings 

Stud walls - internal partitions and separating walls

Reducing sound transfer between rooms and dwellings, which is useful in family homes, home offices, or flats. 

Floors and ceilings

Improving privacy in multi-storey homes, conversions, or office spaces. 

External walls

Limiting intrusion from external sources such as traffic or neighbours. 

Roofs and loft conversions

Reducing external noise, creating quieter living or working areas.

Suspended and Mounted Acoustic Panels

For rooms which require additional sound absorption. These are particularly useful in public spaces or recording/performance spaces.

How Natural Fibres Control Sound 

Absorption through fibre structure

Wool has a naturally crimped texture, while the addition of sisal creates a tangled structure that creates numerous small air gaps. These gaps trap sound waves, reducing reflections and echo within rooms. The structure’s springy properties also resist vibration, slowing the transmission of noise through building elements. In practice, this means the materials absorb sound inside a room and restrict noise transfer to adjoining spaces. 

Mass and density for noise reduction

The combination of density and fibrous structure in Sisalwool insulation provides both effective absorption and resistance to airborne sound. Denser materials make it harder for sound waves to pass through walls or floors, while the open fibre network softens echoes, enhancing acoustic comfort. 

Acoustic Testing of Sisalwool Insulation

Independent laboratory tests have assessed both the sound absorption and airborne sound insulation of Sisalwool. 

Sound absorption tests

Performed in a reverberation chamber (BS EN ISO 354:2003), these tests measure how quickly sound decays in a room with and without insulation. Absorption coefficients (αw) indicate how much sound energy is absorbed rather than reflected. Sisalwool insulation performs particularly well at mid-to-high frequencies, improving interior acoustics. 

Airborne sound insulation tests

Conducted on laboratory-built wall and floor build ups (BS EN ISO 10140-2:2021), these tests measure how much sound passes through a partition or floor. The Sound Reduction Index (Rw) quantifies resistance to airborne noise. For example, a basic timber stud wall with 50 mm of Sisalwool insulation can achieve Rw ≈ 40 dB, while a basic timber floor with 100 mm can achieve Rw ≈ 42 dB. These values increase when additional materials such as thicker plasterboard or sound board are used. See our acoustic datasheet for more information. 

These results demonstrate that Sisalwool is effective at both absorbing interior noise and reducing noise transmission between spaces. 

Compliance with UK Building Regulations 

Sisalwool insulation has been tested according to recognised international standards (UKAS accredited labs) with results that intend to provide support to meet Part E requirements for airborne sound insulation. Its combination of absorption and resistance allows it to perform effectively in walls, floors, and ceilings while also maintaining breathable and non-toxic characteristics. 

Advantages Compared with Conventional Materials 

Why choose Sisalwool? 

Sisalwool offers measurable acoustic benefits in addition to thermal performance. Its ability to absorb sound within rooms and resist transmission between spaces makes it a suitable choice for residential and light commercial projects. Independent laboratory testing provides reliable evidence of performance, supporting confident specification for compliance with Part E of the Building Regulations.