As a manufacturer of bespoke timber windows and doors, we are increasingly being asked about acoustic performance, but what do we mean by acoustics and what should a self-build customer or developer consider?
There are a number of things to consider. Firstly, what kind of noise do you want to stop? Where is it coming from? Where do you want to keep the noise out of? Often most sound will come through a window if it is single glazed, poorly fitted or has trickle vents. However, windows are only part of what you need to consider with walls, ceilings, the roof, air vents and fireplaces to take into account too.
What is noise?
Acoustic noise can be anything from quiet but annoying to loud and harmful. This ranges from the annoying sounds coming from someone’s headphones on a train to a live rock concert or a jet engine at close quarters. Physically, sound is a longitudinal, mechanical wave and can travel through any medium, but cannot travel through a vacuum, which is why there is no sound in outer space! A normal conversation is 60dB, a lawn mower is about 90dB and a loud rock concert is about 120dB. In general sounds above 85dB are harmful, depending on how often you are exposed to them.
Why and when is acoustic performance an issue?
When building a home, it is important to consider the areas of your home that need to be quieter, for example, the bedrooms would need to be quieter than the kitchen and living areas. It sounds obvious but noise comes from inside and outside the building, with household appliances like refrigerators and televisions indoors and traffic noise, aeroplanes, even school children at play outdoors. Think about the location of your new home. Is it on a busy road? Is it next to a school and if so, does it matter if there is noise during the day time? Is there a pub or restaurant nearby that is likely to create a noise disturbance at night? Unreasonable levels of noise can have serious health consequences and it is important to consider this in your planning.
What do Building Regulations and Planning say?
Part E of the Building Regulations “resistance to the passage of sound” can be found online or is available from local planning authorities. It states: “Dwelling houses, flats and rooms for residential purposes shall be designed and constructed in such a way that they provide reasonable resistance to sound from other parts of the same building and from adjoining buildings.”
It also states that construction of internal walls between a bedroom or a room containing a WC and other rooms should provide reasonable resistance to sound.
Extensive guidance is also given on the types of materials to use in the construction of external and internal walls and floors in a new build as well as guidance on conversions where there is a change of use, for example a large house being converted into flats. If an existing living room will become a bedroom, it could require wall and floor insulation treatment. For some historic buildings, it may not be entirely possible to improve the sound insulation to the standards set and guidance should be sought from your local planning office.
What levels of noise are acceptable inside a home?
World Health Organisation Guidelines state that a maximum of 40dB is recommended at night which corresponds to the sound from a quiet street in a residential area. People exposed to higher levels (55dB) similar to the noise from a busy street long term can trigger elevated blood pressure and heart attacks. Acceptable levels in reception rooms and other general living areas are below 50dB.
How to reduce noise from outside?
Mass is the best way of absorbing sound which means a thick concrete block wall stops more noise than one made of a light insulated block. Therefore, with a window, the thicker the glass, the more sound will be absorbed. Windows and doors generally perform less well than walls and roofs. Sound travels through any place there is air leakage which means that a window that performs well in an air test will also perform well in an acoustic test. When selecting a window product, ensure that the whole window has been tested and not simply the glass unit.
The style of window also affects the acoustic performance and generally casement windows offer better performance because they form a tighter seal. However, our patented seal on our sliding sash windows means they are as good as most casement windows.
Nevertheless, most other manufacturers struggle to provide a sliding sash window that performs as well acoustically as a casement.
Double or triple glazing provides effective soundproofing and argon is preferable to air because it is a more dense gas. If you want the optimal acoustic performance, krypton is an option but the difference in acoustic performance is marginal.
In terms of glass types, standard annealed glass is sufficient in most situations, but thicker glass is best and laminated glass gives optimal performance with an enhanced acoustic interlayer. An acoustic sound engineer can be employed to advise on this, if required, and they will define the required Octave which we will refer to our detailed test data and accurately specify the best product.
Many glass manufacturers have their own data but it is important to bear in mind that this is for the centre pane only and will not take into account the frames and sashes. Pricewise, thicker glass is more expensive as is triple glazing and acoustic laminated glass.
Correct installation is key
The most optimally designed and manufactured window is only going to be effective if it is installed correctly. If there are gaps between the window and the wall, there is an opportunity for sound to enter the building. All possible entry points for noise should be sealed during and after installation, including gaps in and around the window frames and walls. It is essential to ensure the opening is level, free of debris and any gaps are filled to maximise performance.