How to comply with regulations on ventilation acoustics?

How to comply with regulations on ventilation acoustics

By Ruth MacEachern

Product Manager

The initial 2010 version of Approved Document F, the government’s document outlining building regulations relating to ventilation and indoor air quality, stated that “the noise caused by ventilation systems is not controlled under Building Regulations”.

In acknowledgment of the importance of preventing excessive noise, this has since been replaced with a set of guidelines aiming to minimise noise. The document now states that mechanical ventilation systems should be “designed and installed to minimise noise”. While this is arguably vague, it cannot be denied that noise from mechanical ventilation systems can pose annoying problems, representing a major cause for concern for both installers and end users.

This edition of our blog will outline the relevant standards and guidelines, while also providing practical tips and advice on how to ensure compliance, increase efficiency, and prevent sound from your ventilation system from becoming a nuisance.

How big a problem is noise from mechanical ventilation systems?

There has been a significant amount written regarding the acoustics of mechanical ventilation systems, and the general consensus is that excessive noise is one of the key factors in preventing their uptake, or even preventing their use after installation.

Brown & Gorgolewski report that “27% of respondents who had disabled their MHRV did so because of its objectionable noise”, McGill et al. include noise in their list of MVHR shortcomings, and in a study of 40 low-carbon homes, Baborska-Narozny and Stevenson found that “30% of occupants reported switching off fans because of noise”. The positive effects of MVHR systems on occupants’ health and with regard to the environment have been equally well documented. If we are to capitalise on the many benefits of such systems, it is essential that noise emissions be considered and appropriately addressed.

How loud is too loud?

An article published in the International Journal of Ventilation, entitled “How loud is too loud?”, identifies a list of potential causes of excessive noise in ventilation systems. These include problems during the:

• design,
• procurement,
• installation,
• commissioning and
• operation of a mechanical ventilation system.

Evidently care must be taken during all steps of a mechanical ventilation project to ensure it complies with regulations on ventilation acoustics The Noise Policy Statement for England refers to a Significant Observed Adverse Effect Level, the level above which noise exposure can have a significant adverse effect on health and quality of life. While document F does not require noise testing, it does offer guidelines, stating that a ventilator operating under normal conditions should not produce noise levels in excess of 30 dB (A) in noise-sensitive rooms such as living rooms and bedrooms, and 45 dB in less sensitive rooms.

Many manufacturers and installers suggest playing it safe in this regard, by aiming for a level of around 24 -26 dB (A). Irrespective of the benefits with regard to alleviating the annoyance of continuous background noise, reducing noise emissions will ultimately have an beneficial impact on the overall efficiency of the system. Our article discussing the importance of energy-efficient ventilation can be consulted here.

How to reduce the noise generated by a ventilation installation

Below you will find a list of tips and essential practices that will assist you in planning and implementing an efficient mechanical ventilation system in your build, keeping unwanted noise to a minimum.

• Take care when selecting the equipment and specifying a ventilation unit that is too small or large for the building may produce excess noise
• Ensure that the ventilation unit is appropriately positioned and installed so as to avoid excess vibration
• Fan units should be appropriately sized and installed
• Choose soundproofing or sound absorbing materials for your vent or duct work
• Insulate the ducts with liners & vents with acoustic foam
• For final connections, there is the option to use appropriately insulated acoustic flexible ducting. This must be kept to a minimum if used.
• You must also ensure that ductwork is appropriately dimensioned and is as airtight as possible - the more airtight your ductwork, the easier it is to control pressure loss and acoustic noise transmission
• When commissioning your system, use appropriate technical measuring methods to determine sound levels  – do not rely on your ear
• Determine permissible sound levels in the various rooms in advance, and take appropriate measures to counteract excessive noise. These might include silencers to control duct noise transmission.
• Instruct end users to regularly have the system cleaned and maintained, as a build-up of dust can affect air flow, resulting in an increased noise level.

If in doubt, the EnviroVent experts can help

While there is no such thing as a silent ventilation system, there are a wide range of noise-insulating wraps, and silencers that can help attenuate excessive noise. It is better to prevent noise from becoming an issue by tackling it at source, during design and installation, before resorting to methods to address an already noisy system. If you have any questions or require assistance with regard to selecting products, or dimensioning and planning your installation, the experts at EnviroVent will be happy to assist you. And for an introduction to the world of mechanical ventilation, check out our beginner’s guide, here.