Building standards - non-domestic buildings - ventilation: research

Project to identify any evidence of where the guidance in Standard 3.14 needs to be updated in order to provide greater assurance that adequate ventilation is provided in new non-domestic buildings, which mitigates the transmission of infectious diseases such as COVID-19.

This document is part of a collection

Survey results

1. Background

An online survey was conducted from 17 February – 22 April 2022 by the University of Strathclyde and was distributed and collated with the assistance of Six-Cylinder Research. The questionnaire was distributed to around 1,500 CIBSE members in Scotland and the UAE, and to the CIBSE HVAC Systems Group (330+ members) on LinkedIn and via our own networks, mainly in Scotland. Initial mailings were followed up with reminder group mailings plus specific targeting of individuals from whom we hoped or expected to receive a response. Responses were received from 21 people in total; whilst this was much lower than expected, the responses were thorough, providing an interesting insight into industry practices and perceptions. The findings are outlined below. A complete set of responses is provided in Appendix A.

2. Responses to questionnaire

Q0. Primary role of respondents

Figure 3. What is your primary role in relation to the consideration of ventilation in buildings

Bar chart showing the primary role of respondents, including design (52%), operation (24%), maintenance (24%), policy (19%), other (19%), and manufacture (5%).

Over 50% of respondents' main role with regards to the ventilation was in design, followed by maintenance (24%) and operation (24%). Other roles included energy (5%), performance standards (5%) and air leakage of buildings (5%), as illustrated in Figure 3.

Q1. What design guides and technical literature on ventilation do you currently refer to and apply when:

CIBSE ventilation guidance was referred to and applied by most respondents (62%) when designing new non-domestic buildings. Other ventilation guidance used by respondents include ASHRAE, Part F, Scottish Building Technical Standards, SHTM03, HTM03, BB101, BS EN 16798-3, TM52, BCO Guides, Passive House, WELL, BREEAM and Net Zero Public Sector Buildings standard.

When maintaining or assessing ventilation provision in existing non-domestic buildings, additional guidance documents were mentioned, including BSRIA, REHVA, BESA SFG20, HSE publications and TM26.

Q2. Do you face challenges regarding accessing appropriate design guides and technical literature when designing ventilation systems for new non-domestic buildings?

One third of respondents stated that they face challenges accessing appropriate guidance when designing ventilation systems for new non-domestic buildings. Some highlighted the complexity of meeting regulations, emphasizing that as a result, the wrong choice is often made. As explained by one respondent,

'While accessing the actual documents is not an issue, much of the guidance during COVID has been unhelpful, conflicting, and generally unworkable. This causes issues and conflicts between various groups. Resolution eventually comes from pragmatism, not necessarily being able to fully align with recommendations and putting in mitigation measures. Pre-pandemic nobody knew what ventilation was, now everyone is an expert and has an opinion. Every stakeholder group has its own blend of guidance. We need definitive guidance, and whether it is retrospective or not'.

Challenges concerning the design of hybrid ventilation systems was mentioned:

'If designing a hybrid, non-standard solution such as mixed mode part mechanical and part natural system then being sure of the performance can rely on manufacturer's data and sometimes dynamic simulation. These can be contentious when using them to demonstrate compliance with standards.'

'Non-domestic building types e.g. Schools, Hospitals and commercial uses etc. have different Ventilation standards which traditionally Architects have deferred to M&E Building Services Engineers. Recently there have been moves away from Mechanical on to Natural forms of Ventilation or more accurately mixed (HYBRID) systems.'

To resolve the challenges of accessing appropriate guidance, some respondents explained they typically design to the highest standards or agree a minimum standard for air quality and monitor it (10%). One respondent stated that to resolve challenges, they discuss the issue with other like-minded professionals or conduct on-line research.

Q13. Need for new ventilation guidance: What existing guidance to you find most reliable for managing indoor air quality and do you think these are sufficient to reduce transmission of airborne infectious diseases? If not sufficient, what is lacking?

The need for new or additional knowledge and guidance regarding the design, operation or maintenance of ventilation systems as a result of the COVID-19 pandemic is clear, as illustrated in Figure 4. In particular, the need for technical guidance for ventilation system design and the revisitation of standards with infection control in mind were highlighted:

'There has been emergency interim advice on operating ventilation systems in the pandemic, but there is no consensus on what the future of ventilation system design should be. This is now required'

'There has been little technical advice, more advice focused on the user'

'Guidance is generally not available - standards need to be revisited specifically with infection control in mind (additional to thermal comfort, TVOCS/CO2)'

'Information not readily available'

'I don't think existing guidance links enough to airborne pathogen suppression/transmission'

'CIBSE guides are generally the best, but these do need reviewed to see if any changes need to be made in light of the pandemic. For example, the generally accepted figure of 8 litres per second per person of fresh air as being adequate for dilution of contaminants needs to be verified again'

Figure 4. The COVID-19 pandemic has placed a greater emphasis on good ventilation as a means of mitigating airborne transmission. Has this resulted in a need for new or additional knowledge or guidance regarding the design of new ventilation systems and/or the operation and maintenance of existing ventilation systems?

Bar chart showing the percentage of respondents who stated 'Yes' (81%) and 'No' (19%).

Q5. The COVID-19 pandemic has placed a greater emphasis on good ventilation as a means of mitigating airborne transmission.

Has this resulted in a need for new or additional knowledge and guidance regarding the design of new ventilation systems and/or the operation and maintenance of existing ventilation systems?

Some respondents noted the need for improved monitoring of CO2 or air quality in buildings:

'Guidance is improving however believe there should be more focus on specific targets for air quality relative to not just CO2 but VOC's, particulate matter and potential ozone & nitrogen dioxide depending on the building type/space activity. There needs to be a better regulation and more scientific approach on the deployment of air quality monitoring/sensing technology'

'I would have liked to have seen CIBSE Covid guidance reinforce the need for colour indicating CO2 sensors in occupied spaces such as open plan offices and classrooms'

Nevertheless, the usefulness of CIBSE, SAGE, BS EN 16798-3 and/or REHVA guidance was emphasized:

'Guidance documentation provided by CIBSE and REHVA provided a good basis to advise clients on how they should be operating and maintaining their buildings during the pandemic'

'CIBSE covid guidance has provided good advice on design and modifications to existing systems'

'CIBSE has provided valuable information'

'CIBSE guidance has been helpful, however there is still some speculation as to what should be used'

'BS EN 16798-3:2017 provides useful assessment process for ventilation rates and filtration depending on the outdoor air quality. It is not user friendly to understand, but strategy is good'

Q3. Do you face challenges when inspecting and maintaining existing ventilation systems?

Figure 5. Do you face challenges when inspecting and maintaining existing ventilation systems?

Bar chart showing the percentage of respondents who stated 'Yes' (65%) and 'No' (35%).

65% of respondents stated that they face challenges when inspecting and maintaining existing ventilation systems (Figure 5). Insufficient access was highlighted as a key issue (25%), followed by a lack of accurate 'as built' and commissioning information (20%). As one respondent explained,

'Existing ventilation provision within tenant demised spaces which are maintained by the landlord are rarely easy to access, inspect, maintain, clean, check fire dampers etc. and this is further hampered by tenant fit outs paying little or no cognizance to such considerations'.

Other challenges mentioned include, 'incorrectly commissioned BMS sensors and controls', poor installation of ventilation systems, the requirement for intrusive surveys (such as commissioning validation) to determine the performance of existing ventilation systems, and poor upkeep of operation and maintenance manuals.

Respondents provided the following suggestions to help resolve these issues:

'Coordination for access is critical in some spaces'

'The key issue is that which still pervades the construction sector, lack of credible or accurate commissioning information. Contracts need to be written around much stronger carrot/stick approach to this'

'Agree minimum air quality standards and monitor the ventilation systems'

Q4. Has the COVID-19 pandemic affected the way you design and/or maintain ventilation systems?

80% of respondents stated that the COVID-19 pandemic affected the way they design and/or maintain ventilation systems. For instance, an increased emphasis on mechanical ventilation solutions was noted, as explained by one respondent,

'Natural ventilation in non-domestic buildings is less likely to be considered viable as good ventilation rates cannot be guaranteed - resulting in more use of mechanical ventilation'.

This is supported by other respondents, who stated,

'Reinforced belief that MVHR in winter is the only way to provide safe air flows in buildings, natural ventilation suits summer only'

'Natural ventilation was popular but now definitive and positive air changes seen as necessary'

'There is a tendency to assume that mechanical is now required to provide ventilation in cold weather where the heat loss or draughts from openable windows is a problem'

Some respondents highlighted the move towards greater ventilation rates and greater attention to monitoring of ventilation performance in practice:

'Much greater ventilation rates applied'

'We are more likely to insist that higher ventilation rates are required'

'More focused checks on air movement within occupied spaces, filtration levels, frequency of change and the like'

'Enhanced ppm, additional CO2 monitoring, additional works to spaces'

'Consideration of enhancing fresh air rates for mechanical ventilation systems e.g. aligning with well-being standards such as WELL'

The move away from recirculation of air was also mentioned:

'Recirculating systems are now probably out - although there can be misunderstandings over these and what actually constitutes 'recirculating' in a way that is detrimental to infection spread'

'No recirculatory systems in schools serving more than one space now'

'We currently operate on 100% fresh air supply in accordance with CIBSE/REHVA guidance -this has a substantial impact to our energy burden'

'Carefully consider of appropriateness of using recirculating systems'

Q6.Typically, how does the building type and the activities within it affect:

a) the design and operation of the ventilation system in new buildings and

b) the inspection and maintenance of ventilation systems in existing buildings?

Do you feel that this has changed due to the COVID-19 pandemic?

Building type and activities are fundamental when considering the design, operation and maintenance of ventilation systems in new buildings. The importance of occupancy levels, susceptibility of occupants, activity level, user groups, pollutant sources, building orientation, building form, room volume, access, energy targets and indoor environmental requirements (temp, RH, pressure differentials) were acknowledged by respondents:

'SAP determines this anyway as that will determine the efficiency of the building and therefore the ventilation system. Orientation, size, people, use, all have a bearing. Given most systems are continual nowadays, they don't particularly require user involvement'

'Building type dictates occupancy that will identify higher risk groups requiring increased levels of ventilation'

'Occupancy density, activity type (e.g. sedentary or active), vulnerability of occupants (e.g. healthcare setting or nursing homes)'

'Pollutants vary by building type'

'Occupancy & activity levels may impact on the design and operation of ventilation systems. Environmental conditions (temperature, humidity, pressure differentials) for spaces and building types will also impact on the design of ventilation systems. These requirements will also impact on the complexity of the system, zoning and controls'

'Building type/activities may impact on the regularity/frequency of maintenance depending on the user group or function of the space. Maintenance and inspection requirements may also be more onerous depending on the space/activity type e.g. healthcare buildings having more stringent inspection and maintenance requirements governed by SHTMs/HTMs, health &safety guidelines dictating level and regularity of inspections & maintenance (e.g. LEV systems) and other industry/sector specific requirements (e.g. licensing requirements for facilities like pharmaceutical production facilities)'

Most respondents (72%) feel that the impact of building type and activities has changed due to the COVID-19 pandemic. Reasons mentioned include: i) an increased focus on inspection and maintenance, ii) a move away from natural ventilation strategies, iii) increased attention to the impact on winter thermal comfort of natural ventilation, iv) more monitoring of CO2 and airflow rates, v) better awareness of the importance of ventilation and building performance, and vi) an increased focus on air distribution and air cleanliness.

Q7. Clients' concerns: Do clients who engage ventilation professionals currently have any concerns about the extent and quality of the guidance and advice that is available to them on ventilation and the transmission of airborne viruses such as COVID-19?

Some respondents highlighted concerns from clients regarding the extent and quality of ventilation guidance and the transmission of airborne viruses, such as COVID-19. Concerns were raised regarding the availability of ventilation guidance for a post-pandemic world:

'We are aware of Clients seeking advice on how they should approach designing, maintaining and operating their systems in a post pandemic world. The guidance produced in response to the pandemic was intended to deal with short term measures during the pandemic during reduced building occupancy and operations. The recommendations and measures implemented may have had a potential impact on building energy consumption and associated carbon emissions. Feedback from Clients is that there is a lack of guidance in relation to ventilation that takes account of lessons learned from the pandemic and how that can be applied to ventilation design, operation and maintenance.

Q8. Impact of building users: Do you perceive that owners/operators of buildings know where to source expert knowledge to inspect and advise on the ventilation system in their building?

Respondents were asked if they believe owners/operators of buildings know where to source expert knowledge to inspect and advise on the ventilation system in their building, of which only 35% answered 'Yes'. Some suggestions were made on how this might be improved, including the establishment of a register of qualified individuals or a non-commercial trade-body for ventilation:

'Perhaps a register of appropriately qualified individuals/companies would be an appropriate route to consider?'

'Start with providing this information to them, perhaps when a local or central authority has to write to owners/operators of buildings to collect property taxes and service charges'

'Public information with good visualisation/graphics can help to make tangible something which you cannot ordinarily see'

'A non-commercial ventilation-specific trade body needs to be established'

'Make sources more widely available and in plain English, for example cut out


'CIBSE need to be at the forefront here letting people know where the expert knowledge is'

'Reference to CIBSE Member consultants made more well-known'

It is interesting to note that most respondents (85%) do not believe occupants can be relied upon to interact with the building and take specific actions in relation to ventilation to reduce infection risk. Some highlighted the trade-off between natural ventilation and thermal comfort:

'This will mostly apply to natural ventilation. Even when there is a high risk of infection thermal comfort will always take precedence so even if a user is advised to open a window, they will shut it as soon as thermal comfort is compromised. Automatic control is better'

'In naturally ventilated buildings, people won't open a window if it's cold. As a firm of M&E Consultants in a naturally ventilated building, our mechanical engineers need to be reminded to open the window, they don't do it as its cold, draughty & noisy when they do'

'Buildings get cold when windows are opened. People don't open them - but more so than pre-pandemic'

Others noted a lack of knowledge or understanding among occupants to operate ventilation systems effectively:

'Some occupants will be infants and others will not have the cognitive ability to understand. They cannot be relied upon to interact with the building. Others will be visitors, who are unlikely to take specific actions unless there is an emergency'

'Each building is different, and the effectiveness of occupant interaction is very much dependent on occupant familiarity with the space/surroundings they are within, the frequency of time spent in the buildings and the confidence & awareness of individuals to take actions to reduce infection risk. This would require a lot more education of building users on the principles of ventilation and how they may be relevant to the spaces people occupy'

'Lack of knowledge of the systems and measures to take'

'Lack of understanding and knowledge, and mostly apathy'

'May be beyond their pay grade and it is for others to worry about'

'Actions taken in good faith may have a negative outcome. Some occupants may be concerned their actions could harm others if they get it wrong'

While others noted issues with control of ventilation:

'Okay if there is a window to open, but building users in general have no control over building ventilation'

'Individual operation of natural ventilation or temperature control systems is deemed to be selfish and inconsiderate'

'Having some kind of warning or information about air quality is one thing, being able to act upon it is another. There may be a tendency to ignore the warning, at least for a while, if it is inconvenient and too difficult and disruptive to take action'

Q9. Carbon dioxide monitors: Do you believe that CO2 monitors are useful in identifying poor ventilation and alerting building users when indoor air quality drops to undesirable levels?

Q10. Do you believe that building occupiers/occupants are likely to link higher CO2 levels with concerns about risk of infection?

Q11. Do you believe that occupants can be relied upon to interact with the building and take specific actions in relation to ventilation to reduce infection risk?

Q12. Beyond CO2 monitoring, what other methods may be used to demonstrate an effectively ventilated building?

Respondents were asked a series of questions relating to perceived indoor air quality (IAQ) and their views on the role of CO2 monitors in identifying poor ventilation and whether or not occupants were likely to make the link between CO2 levels and IAQ and act upon this to improve their indoor environments. They were also asked what other methods beyond CO2 monitoring may be used to demonstrate an effectively ventilated building. The responses, as summarized in Figure 6, evidence a good level of knowledge and understanding of ventilation assessment methods among respondents, ranging from pollution measurements (VOCs, PM), airflow assessment (tracer gas, pressure differentials, smoke testing, airflow) and ventilation system commissioning (maintenance and records).

Figure 6. Beyond CO 2 monitoring, what other methods may be used to demonstrate an effectively ventilated building.

Radial diagram showing different methods to demonstrate effective ventilation, including <abbr title=VOC monitoring, airflow measurements, temperature and RH, smoke testing, tracer gas dilution tests, measuring pressure differentials, PM2.5 / PM10 monitoring, health, good maintenance and records, and PIR/timed boosts.">

Q14. Self-regulation of ventilation systems

Respondents were asked to provide their views and/or experience of the extent to which ventilation systems can be self-monitoring, removing the need for occupant interaction and monitoring. Most agreed, highlighting the benefits of sensor-based ventilation control (PIR, CO2, temp, RH) for both indoor air quality and energy performance:

'Self-monitoring is desirable, the use of VAV system can help balance energy demand'

'A continual system will be self-monitoring as it is providing ventilation constantly, this can also be aided by any monitor you wish, PIR, humidity sensor, timed boost, etc.'

'We have been designing ventilation systems with variable air flow to suit a building occupancy, internal temperature and occupancy CO2 for over 20 years, its the most energy effective way to do it'

'Yes, we have presence/absence detection & CO2 monitoring which are used to manage ventilation. It works and is reasonably reliable'

However, some important caveats were noted concerning the maintenance and validation of systems:

'It is critical where there is a reliance on self-monitoring systems that appropriate maintenance, inspection and validation of systems is regularly undertaken relative to the type of building/space type'

'Yes, this can be effective and desirable, providing systems and sensors are well maintained'

'Automatic systems can work well but the maintenance of the controls and the ventilation equipment needs to be improved to ensure they work as intended. Such systems probably would need a check on a six-monthly basis.'

'Tragically there is evidence the world over that the ventilation systems in use failed. The result was the pandemic. Pressure monitors in negatively and positively pressurised rooms were not accurate, and assumptions of good ventilation and IAQ were made, when clearly this was not the case, as hospitals, educational centres, offices, and other places of work became infection hot spots. Every building has unique characteristics, and every building will need a bespoke solution, based upon permeability'

Moreover, the benefit of occupant control in certain circumstances was also highlighted:

'This type of system doesn't need user involvement, but we shouldn't discourage user involvement as we need to educate as to why we need ventilation anyway'

'Self-monitoring systems that are automatically controlled can be desirable however is very much dependent on the building type, activity levels and the buildings complexity. In many instances simpler, more cost-effective user driven controls may be appropriate particularly within a building where the occupants are familiar with and/or well educated in the design & operational intent of the ventilation systems.'

Q15. Changes to existing ventilation systems: Have you encountered situations where physical changes to an existing ventilation system have been needed to improve ventilation in response to concerns over transmission risks?

If yes, was this to a system designed to current building regulations (post-2015) and current industry design guides and operable as designed?

If yes, can you provide a brief summary of the changes made and why they were recommended?

73% of respondents stated they had encountered situations where physical changes to an existing ventilation system had been needed in response to concerns over transmission risks. Changes required included: i) disabling air recirculation, ii) adding direct supply to extract only systems, iii) increasing air throughput, iv) installation of CO2 monitors, v) adding fans to unventilated spaces, vi) refurbishment of AHUs, vii) improving filtration, and viii) installation of air cleaning devices. As explained by respondents:

'Some spaces had extract ventilation only, using make up air from adjacent spaces, so we have redesigned and added direct supply to the spaces.'

'Buildings with recirculation air handling units have had the recirc[ulation] ability removed to avoid transfer. Thermal wheels have been turned off to avoid cross contamination and Fan Coil Units (FCU's) that recirculate air through ceiling void have been changed to ducted.'

'It was a system that had a recirculating facility in a fresh air system, it wasn't really needed as there was a thermal wheel on the system in any case, we had to disable it to comply with the COVID guidance issued in the summer 2020.'

'System designed pre 2015 and in line with standards current at the time. Looked to increase air throughput by a variety of means bearing in mind constraints imposed by building fabric.'

'Wall/window fans added to unventilated spaces, AHUs refurbished with new efficient quiet fans, plate heat recovery, new heater batteries and CO2 monitor controls. Designed in line with current practice.'

'Portable or plug-n-play air cleaning devices to enhance the current ventilation provision. These were recommended for 'no' or 'below' ventilation standard situations.'

'System was a sealed building and had central supply with recirculation to up to 10 classrooms. Required setting to full fresh air, increase in supply temp to heating coil in main AHU and improved filtration at central AHU.'

'Existing system in schools - e.g. where vents in doors and walls allow air to transfer between classrooms.'



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