Is the Government's sustainability drive rattling acoustic standards? Paul Absolon, technical director of CMS Acoustic Solutions, offers B&E some sound points to keep ahead of the game.

Sustainability has been lifted to the top of the agenda, most notably in construction where government targets are already in place to help ensure minimal environmental impact at every stage, from the materials used for construction through to building operation post-completion.

While the term sustainability is widely used, its meaning is also far-reaching. Even in the very specific domain of sound insulation, sustainability takes on a variety of guises. For example, where the Code for Sustainable Homes is concerned, sustainability for noise standards requires that homes are adequately soundproofed, to help reverse the trend of people moving away from problem areas because of nuisance noise.

Regarding sound control, sustainability can also be viewed in relation to environmental impact, from product manufacture through to longevity of performance. Following the introduction of Part E in 2003, these factors have become increasingly salient, because the cost-driven construction industry has launched a number of low-cost, low-end and often poorer quality acoustic materials. These have been most notable in relation to impact sound, with an alarming number of low-cost resilient flooring products entering the market.

Environmental factor
Although many low-end acoustic flooring materials cost less to purchase than higher end systems which incorporate cork, recycled rubbers and polyurethane, the manufacturing methods involved in their construction can have a detrimental effect on the environment.

The effects of low-end acoustic flooring systems upon the environment start with the manufacturing process, with many unable to state ‘Zero ODP’ (Ozone Depletion Potential). Substances with ODP degrade when they eventually reach the upper segment of the atmosphere (the stratosphere) and harm the ozone, which acts as a filter for UVB radiation.

Furthermore, many lower end products do not have ‘Zero GWP’ (Global Warming Potential). GWPs measure the influence that greenhouse gases have on the earth’s natural temperature, including the ability for gas molecules to absorb or trap heat, and the length of time they remain in the atmosphere before being removed or broken down. The GWP methodology allows the contribution that each greenhouse gas makes towards global warming to be assessed.

Moreover, whether a material is lower end or otherwise, it is not uncommon to find its manufacturing methods have borne a heavy burden upon the environment. To reduce the environmental impact of product manufacture, in-house production processes should be regularly reviewed and improvements to equipment frequently made to ensure operations are as environmentally friendly as possible. Simply servicing equipment on a regular basis can reduce the amount of energy that is used during the manufacturing process.

Long-term performance
Thinking carefully about the environmental impact of product manufacture is only one factor that determines the sustainability of a product, as its performance level and longevity must also be addressed.

The Code for Sustainable Homes aims to improve on Part E standards by awarding points for increased sound reduction. As a result, developers will no longer be challenged with just meeting Part E, they will be encouraged to exceed the minimum impact and airborne sound requirements. The majority of lower end systems, however, will fail to deliver the superior acoustic performance demanded by the code.

The lifespan of some lower end systems is relatively poor compared to those at the higher end. The former may meet Part E in the first instance, but some materials have been known to either ‘bottom out’ or stiffen significantly once loads are applied to floor surfaces – ultimately compromising acoustic performance.

Stiffening is commonly caused by the screed-penetrating the resilient layer. That adverse effect can be offset by installing a polythene membrane over the chosen isolating layer, guidelines for which should be provided by the material manufacturer.

Longevity of system performance should be carefully evaluated whether using an acoustic underlayment or under screed material. However, particular caution should be exercised with screed isolation, as sound testing is normally conducted shortly after the screed has been laid over the resilient material. At this point the system may deliver adequate sound insulation, but, dependent on the material’s composition, has the potential to fail over time. From the developer’s perspective, this will result in expensive remedial works should occupants lodge complaints about nuisance noise postcompletion.

As low-end materials only perform in the short term, the first the developer will know of a sound insulation problem is when occupants lodge complaints about unacceptable noise levels. This is because lower end resilient under screed materials are lightweight and therefore have a severe tendency to creep. Such deterioration can be quite rapid, but is accelerated by the application of a load, such as people and furniture.

As loads are unlikely to be applied until occupants are in situ, any acoustic remedial works will not only have to cover the cost of resources and materials, but will also have to account for the re-housing of occupants and compensation for the inconvenience.

Remedial situations such as these can easily be avoided. Where a resilient screed layer is being used, relatively high-density materials should be selected. Low density in the context of acoustic under screed materials is deemed to be below 100kg/m3, while high density would generally be above 500kg/m3.

Recycled rubber tyre crumb under screed materials tend to be high density and offer a resilient longevity that will outlive the life expectancy of the building where the material is installed.

Defining recycled
In the first instance, developers should be aware of what qualifies a product as recycled. Some manufacturers claim scrap materials that are reused in the production process constitute post-industrial waste, when this is not the case.

While reusing scrap material is good environmental practice, since it minimises the amount of waste from the plant, it does not strictly qualify as recycled content. A manufacturer can only state their products are made from recycled matter when the materials have been recovered or diverted from the solid waste stream, either at postconsumer or post-industrial level.

To protect the environment and ensure long-term product performance, best practice is to use acoustic flooring treatments that are manufactured from recycled rubber materials.

Comprising post-consumer shredded and cleaned styrene butadiene (SBR) tyre rubber and post-industrial ethyl propylene dione monomer (EPDM) that is bound with a polyurethane-based binder, the manufacturing process is energy efficient and creates minimal or no waste at all, as many production processes utilise the waste
material in other compounds.

The actual recycled content in recycled rubber treatments is relatively high, ranging anywhere from between 30% to 90%.

These recycled rubber crumb compounds are highly durable whilst remaining entirely recyclable. They will not rot or break down over time and their physical properties will not alter. Assuming these solutions are installed in accordance with manufacturer guidelines, they should last the lifetime of the building in which they are installed. This is, perhaps, the true definition of sustainability.