Rob Crampton of Hush Acoustics explains why investment in acoustic insulation will result in a higher level of satisfaction for customers.
Acoustic standards in UK housebuilding have not been upgraded in a meaningful way since the early 2000s. As a result, sound insulation levels in connected homes and within individual dwellings have fallen way behind the improvements seen in many other areas of building, such as thermal performance, security and accessibility.
This is why it is crucial when designing internal and separating floors/ceilings and walls to look to the acoustic standards set by the Building Regulations as an absolute minimum – not a target. Building to a standard that will simply tick the necessary boxes for Building Control sign-off will often disappoint homebuyers and tenants, who rightly expect more given the availability of today’s high performing acoustic products.
In fact, many of the most common complaints from buyers of new build homes relate to unwelcome noise. In individual properties such as detached family homes, it is not unusual to hear owners commenting that impact sound transmission through the house from sources even including light switches is far greater than they were expecting.
Conversion of existing properties is another area where minimum acoustic standards fall short. The boom in adaptive reuse means more and more commercial spaces are being converted into residential – here the requirements for material change of use should not only be complied with, but exceeded. Newly created residential properties will often be above ground floor commercial space, such as retail or hospitality, where the amount of noise generated will vary hugely – in some cases this could render the minimum standards totally inadequate.
In order to exceed the minimum acoustic standards, every project needs to be assessed on its own merit – there is no one size fits all approach.
When a sound wave hits a surface, some of its energy will be reflected and some absorbed. This causes sound vibrations to transmit in buildings in different ways, which is why multiple different materials have to be used to stop their transmission paths.
There are many different floor/ceiling and wall constructions used in construction, each of which can be treated with a bespoke combination of acoustic products to deliver superior results. Some products are designed to absorb airborne sound, with fibrous materials particularly effective, while others work by providing separation. Resilient layers and rubber products are key to reducing impact noise and dense materials like chipboard and plasterboard provide a barrier to soundwaves.
It is also important to deal with the problem of flanking – where sound waves transmit around installed insulation materials. Hence, any sound reduction measure must treat the edges and perimeters of floors and walls with sealants and ‘flanking strips.’
Approved Document E, Northern Ireland’s Part G and Scotland’s Section 5 all stipulate compliance levels for separating floors and walls. In England and Wales, separating floors between new homes and purpose-built rooms for residential purposes must achieve an airborne sound insulation level of 45 dB DnT,w + Ctr. In Scotland, that figure is 56 dB DnT,w (onsite test results). In change of use or conversion, the minimum levels are 43 dB DnT,w + Ctr and 53 dB DnT,w respectively.
The maximum level of impact sound transmission in England and Wales is LnTw 62 dB (56 dB in Scotland). In rooms created by a change of use or conversion, it is LnTw 64 dB (Approved Document E) and 58 dB (Section 5) in Scotland.
The separating walls between new homes in England and Wales must meet a minimum airborne sound insulation level of 45 dB DnT,w + Ctr. This figure is 43 dB DnT,w + Ctr for purpose-built rooms for residential purposes and rooms created by a change of use or conversion.
Scottish properties must meet a higher standard with separating walls between new homes, purpose-built rooms for residential purposes and conversions required to meet the minimum airborne sound insulation level. Homes or rooms created by a change of use or conversion must achieve 53 dB DnT,w.
DON’T JUST COMPLY
All kinds of insulation products have been developed in recent years to target very specific sound transmission paths. When these are combined in the correct way they can help housebuilders to deliver properties that are much more in line with customer expectations.
The combination required will depend on the target performance level and the way the floor or wall is constructed. For example, if the floor is of a traditional timber construction – timber joists with floorboards and a plaster ceiling – typically the treatment would involve creating a floating floor in conjunction with layered plasterboards, resilient bars and sound absorber panels. This will take it from compliance to ‘satisfied customer’ standards.
A concrete or masonry floor/ceiling structure could also benefit from a floating floor approach, but they will often require rubber based products, an MF ceiling system and acoustic battens.
There are a wide variety of standard fully tested acoustic systems available which offer an ‘off the shelf’ solution to different floor construction. However, acoustics can be a complex area, so it is always best to seek specialist advice if you have any uncertainties about whether your proposed sound insulation approach will achieve the results you seek. Getting it wrong can result in costly remedial work if the property fails at the sound testing stage.
Rob Crampton is managing director of Hush Acoustics