Low noise MVHR (mechanical ventilation with heat recovery) has a key role to play in maintaining good indoor air quality (IAQ) with minimum energy consumption.
The parallel pressures of maintaining healthy indoor environments whilst optimising the energy performance of buildings create a number of challenges for building service engineers. This document considers the role of noise from ventilation systems and how this can be minimised.
Indoor work and study spaces are subject to a range of environmental parameters that contribute to the health and wellbeing of the occupants. The parameters that spring most readily to mind are thermal comfort, lighting quality and IAQ but it is now well established that noise levels also make an important contribution. This is especially important for areas that have particular low noise requirements such as libraries, special educational needs (SEN) facilities and health facilities.
The relationship between noise levels and IAQ is becoming increasingly important. As the energy performance of newer buildings is enhanced by improved ‘air tightness’ and better insulation, maintaining good IAQ relies on either mechanical ventilation or opening windows. The latter option is often impractical due to noise and pollution issues from nearby roads.
Given the importance of energy efficiency alongside these factors, MVHR is proving to be the solution of first choice in many applications as it delivers the benefits of mechanical ventilation while recovering most of the heat within the space.
However, many ventilation systems are also intrusive due to high noise levels caused by fans, air movement through ductwork and vibration within the air distribution system. Building services engineers can address these issues by specifying low noise MVHR, such as SAV’s AirMaster heat recovery ventilation units.
Low noise MVHR
Acoustic requirements for schools, as specified in Building Bulletin 93, are a case in point. For example, general classrooms using MVHR equipment have an upper limit of 35 dB(A) for new build and 40 dB(A) for refurbished spaces, falling to 30 dB(A) (new) and 35 dB(A) (refurbished) for spaces intended for students with special hearing and communication needs. SEN calming rooms also have an upper limit of 35 dB(A).
For natural ventilation systems, the noise limit is more relaxed. Additional 5 dB(A) are allowed during normal operation time and a maximum limit of 55 dB(A) are acceptable for no more than 200 hours per annum to avoid overheating, whereas MVHR equipment needs to remain within 45 dB(A).
Nor are these the only types of space that require low noise levels. Clinics and community centres with quiet areas require similar noise levels. People working in standard office spaces can also be adversely affected by noisy ventilation systems.
It therefore makes sense to minimise noise levels for all ventilation systems, paying particular attention to those areas that have especially low noise requirements.
The ideal solution for many such application is AirMaster. At 100% throughput, AirMaster units emit just 35 dB(A) at 1m, reducing to 30 dB(A) at 80% of full throughput. This is achieved by high levels of attenuation in the design of the units, combined with low noise EC (electronic commutation) drive motors that enable modulation between 0% and 100% of full throughput. Moreover, these noise levels will not increase during the operating lifetime of the unit.
AirMaster units can also reduce the ingress of external noises by around 49 dB. For instance, when placed next to classroom windows exposed to traffic noise around 60 dB(A), the muffling effect of direct ventilation units reduces the resultant noise ingress to 7 dB(A).
In projects where environmental noise is likely to be an issue, SAV Systems can provide data to establish the net impact of such noise after passing through an AirMaster unit.