Acoustic Design for Sustainable Buildings, 17/9/15
Notes from presentation at Institute of Acoustics workshop by Jack Harvie-Clark
In the move towards Zero Carbon dwellings, it is necessary to design and construct buildings with lower air permeability and mechanical ventilation with heat recovery. Domestic mechanical ventilation systems have been used in at least 70 % of new homes since 2011, but there are no noise limits for these systems in the Building Regulations. This means that this source of noise is un-regulated, and yet can have serious potential effects.
In the UK we do not have an acoustic classification system, which assigns different levels of acoustic performance to different levels of occupant satisfaction. Many European countries have such a system, and following a large European collaboration project, COST Action TU0901, the pan-European acoustic classification system is in the process of becoming an International Standard, ISO/NP 19488.
The different levels agreed across Europe for the different Classes are shown in the table below.
Class C is the level at which 10 % of people would be dissatisfied with the noise; in Class D around 20 % of people. Many UK practitioners are unfamiliar with the concept that noise levels well below 30 dB(A) may be desirable. Noise levels below 30 dB(A) may not interfere with sleep when someone is asleep; rather they are noise levels that may be annoying while people are trying to fall asleep.
People chose the fan speed that has tolerable noise levels, not the fan speed that is required for sufficient air quality
The slides are available to download from the link at the bottom of the page; the presentation was aimed at acousticians, but most of it should be accessible to non-acousticians. It covers guidance currently used in the UK to determine suitable noise levels from mechanical ventilation systems, and compares these values with other sources of guidance. A literature review of European experience of annoyance associated with different levels of mechanical services noise is presented, and the careful wording of the World Health Organisation guidelines is considered. The current Swedish requirements for low frequency noise limits are highlighted, as an example of what others in Europe are doing to address the problem. The noise limits that will be incorporated into the new ISO/NP 19488 are discussed, being derived from the COST TU0901 programme.
The study by Kurnitski et al (2007) provides the most detailed assessment of satisfaction with ranges of noise levels. This study also found the result that people chose the fan speed that has tolerable noise levels, not the fan speed that is required for sufficient air quality.
This finding is repeated in many studies across Europe that have investigated noise and ventilation. We can benefit in the UK from others’ experience, and it is vital that we do if we are to avoid a negative association with mechanical ventilation in dwellings. Mechanical ventilation is an essential component for energy efficient dwellings.
|Comment received February 2015Hi Jack,… When the unit is switched on, every time you switch a light on it comes on. The noise is unbelievable, I can hear next doors when they switch theirs on. It drives you mad, to the point where you find yourself peeing in the dark since you don’t want the hassle of switching the thing on and annoying the neighbours. When you switch the light on and off even for a second it stays on for about 5 minutes.
…Someone on the estate mentioned to everyone that you can switch it off in the loft. Within 2 days everyone switched it off and none have been on for three years.
Hope this helps,
Download slides here:
Further information from subsequent full length conference paper:
Read more about our research on this subject in Noise and ventilation in dwellings.