How can an Acoustic Consultant assist with Approved Document O and Noise Levels?

Demonstrating Compliance with Part O Regulations 

Approved Document O provides guidance on how to comply with Building Regulations Part O, and outlines measures to reduce the occurrence of high indoor temperatures. 

Compliance with the requirements of AD-O can be demonstrated by using one of the following methods. 

• The Simplified Method; or 

• The Dynamic Thermal Modelling Method 

The correct strategy should be selected according to the development location, whether or not the units/rooms provide ‘cross-ventilation’, and the external noise levels incident on proposed bedroom façades during the night. 

It is therefore essential that a baseline environmental noise survey be conducted at the development site as early in the process as possible. This will inform on the appropriate approach, and level of detail required to achieve compliance.  

A 3D-noise model will then be produced by Omnia, using state of the art noise modelling software CadnaA, to predict the sound levels across the development site and establish the incident sound levels at each sensitive façade (which will help to determine appropriate mitigation measures and inform the Energy/Sustainability review).   

 When Would the Simplified Method be Used?

• The Simplified Method can only be used if the development accords with the requirements set out in in Approved Document O; 

• The external noise levels in the area may prohibit the use of this method, and the more complex/accurate dynamic thermal modelling method should then be employed; and 

• Following the baseline noise survey, Omnia and the instructed energy consultants can review the gathered data and establish the relevant method/approach for the development.  

When Would the Dynamic Thermal Modelling Method be Used?

• The Dynamic Thermal Modelling approach will generally be used where external sound levels prohibit the opening of windows during the night, and for more complex buildings/scenarios where greater accuracy and design flexibility is required; 

• This approach requires the instatement of an Energy/Sustainability expert, who will use CIBSE Thermal Modelling software (TM59) to accurately replicate the form of the building and map it against the potential overheating scenarios; and 

• This tool can be used to work out the potential overheating risk in specific rooms and at specific times of the day.  It is also possible to model different mitigation methods and work out their efficacy, such as glass coatings, shading and shutters or blinds. 

Summary 

Part O requires new residential developments to comply with overheating design considerations in addition to Building Regulations Part E (resistance to the passage of sound) and Part F (ventilation).  Where each of these factors can affect the other, it is appropriate to consider these collective elements in coordination. 

Omnia can provide developers with a detailed Noise Impact Assessment which can be used to gain planning permission and can also be used by your appointed Energy & Sustainability Consultant to complete their thermal modelling. 

Due to the nature of the regulations, it is necessary that experts such as Omnia are consulted early in the development process, and that the relevant disciplines work together to assist in providing appropriate overheating and mitigation solutions. 

Baseline noise surveying must therefore take place in the earliest stages of the project to assist in choosing the suitable approach (Simplified or Dynamic Thermal Modelling Method). 

All new residential developments will now need an acoustic model to inform the thermal assessment – the complexity will depend on the type and number of noise sources surrounding the site.