Overall conclusions and issues to consider
1. Main conclusions
The study aimed to establish what ventilation guidance was being used by industry in practice when designing new or maintaining existing non-domestic buildings. The results of the industry survey suggest a wide range of ventilation design guides and technical literature are being used, from various sources including CIBSE, BB101, ASHRAE, HTM, BSRIA and BS 16798-3.
It is widely recognized that the higher the rate of ventilation indoors, the lower the risk of airborne transmission of covid-19, in particular, for long range (>2m) transmission. As such, the adequate ventilation of a building space should be regarded as the primary mitigating measure against the spread of airborne diseases. Whilst ventilation standards in general may be acceptable, a principal issue is whether these are being met a) in use and b) maintained over time. The general feeling has been that, if buildings were meeting their intended ventilation standards, then Covid-19 transmission risks were minimised. However, in practice there was virtually no reliable data on whether or not this was the case.
Respondents highlighted the requirement for sensor-based monitoring. This is reflected in changes to the Building Regulations in England through changes to Part F (Ventilation) in domestic and non-domestic buildings. There is growing awareness of the benefits of performance monitoring and the need to ensure compliance with legislation in practice. CO2 monitoring is recommended as a cost-effective strategy to help identify spaces with poor ventilation and/or high occupancy, to inform decisions and to support the active management of ventilation in a space.
The second issue is regarding the current level of requirements to ensure that compliance with regulations is maintained over time. For instance, some changes/retrofit that may not trigger a new warrant may adversely affect the ventilation provision. The need for a building 'MOT' is suggested, to establish the idea that buildings, like vehicles, need to meet certain standards, which could go some way towards closing the performance gap. This requirement exists for Legionnaires Disease, for example, to ensure regular assessment of performance under HSE legislation. Respondents highlighted challenges when inspecting and maintaining existing ventilation systems. The lack of accurate commissioning information and performance data is a key issue, resulting in a lack of ability to monitor and verify compliance over time.
This raises the question as to whether there is a need for a requirement in the regulations regarding the provision of a maintenance plan, to go some way to ensure regular inspection, cleaning and maintenance of ventilation systems. Whilst Standard 3.14.10 requires key information on the ventilation system to be provided on completion, including instructions of how and when maintenance should be carried out, a maintenance plan would help determine how this will be achieved in practice. This could also be related to a possible requirement for a communications/labelling strategy, especially for naturally ventilated spaces to make clear what the ventilation system is and how it is operated. This could adopt the same approach as the domestic energy 'quick start guide'.
2. Summary of suggestions for updates of guidance
- Recommend phasing out of recirculation of air and replacement over time with heat exchanger systems which prohibit the mixing of intake and extract air to avoid airborne pathogen transmission
- An increase in the required mechanical ventilation supply rate from 8 l/s/p to 10 l/s/p is suggested for occupied rooms, in addition to the need for greater clarity in the definition of supply rates and consideration of occupancy limits, based on the capacity of ventilation systems.
- The introduction of requirements for CO2 monitoring in multi-occupancy high risk spaces to help identify airborne transmission risk related to poor ventilation and/or high occupancy, to prompt and inform behaviour change. This should be provided with clear guidance and appropriate information specifically tailored to the user group, to enable monitors to be used effectively.
- The consideration of infectious disease transmission in building ventilation regulations through the provision of explicit advice on the risk of far-field (>2m) aerosol airborne transmission. The importance of ventilation in mitigating this risk should be highlighted (e.g. in Section 3.14.1).
- The requirement for a building ventilation maintenance plan, to support the regular inspection, cleaning and maintenance of ventilation systems in practice.
- Provision of a communications / labelling strategy for building ventilation systems (like the domestic energy 'quick start guides') to provide a clear, simple explanation to building users on what the ventilation strategy is, and how to use it. Whilst Standard 3.14.10 requires key information on the ventilation system to be provided on completion, the provision of short, visual instructions (for instance, next to ventilation systems or controls) would help ensure accessibility to all users and support understanding and effective operation of ventilation systems in practice.
- The identification of ventilation performance standards and enhanced measures to ensure that compliance is achieved in use and maintained over time. The introduction of a performance-based framework for assessing ventilation performance in non-domestic buildings (e.g. through an annual building 'health-check' / 'MOT', or for new retrofit works), would help ensure regular assessment of performance and verification of compliance over time.
There is a problem
Thanks for your feedback