Building standards - ventilation guidance: research

1. Executive Summary

1.1 The overall purpose of this work has been to investigate the effect the 2015 changes to guidance in Standard 3.14 has had on: ventilation design solutions and their implementation; occupant interaction with ventilation components; occupant experiences and observations on ventilation systems and indoor air quality; measured levels of indoor air quality within a representative selection of dwellings; and to provide clear reporting of outcomes and recommendations for where improvements can be made.

1.2 The brief specified a start date of March 2021, with the project due to be completed by the end of August 2022. However, restrictions due to the Coronavirus pandemic heavily impacted on the project's delivery since substantial elements of the work relied on access to households. The project has effectively completed in October 2022.

1.3 The literature review (WP1) was completed in April 2021, identifying best practice, emerging trends in this field, and other regulatory standards for ventilation. It highlighted a possible conflict between indoor and outdoor pollution sources when opening windows to dilute and expel indoor pollutants in urban locations.

1.4 The original intention had been to undertake the face to face survey work (WP2) in spring 2021 and to start monitoring (WP3) soon after. However, due to Covid restrictions about essential work, concerns about undertaking fieldwork, and potential reluctance of participants, this work was postponed to Autumn 2021.

1.5 However, with continuing cases, restrictions for fieldwork remained in place, therefore a decision was taken to deliver the WP2 survey as a postal survey. A larger pool of survey addresses (2000 in total) were obtained from records of Energy Certification (SEPCR) - Domestic Extract Apr 2019 To Mar 2020.

1.6 The postal survey was developed, based on previous similar work (REF 2014 Survey), augmented with a face to face survey when restrictions were lifted producing a final total of 138 returns, identifying 57 households interested in participating in the long term monitoring (WP3).

1.7 The survey identified a high proportion of households reporting not having a Carbon Dioxide (CO₂₎ monitor fitted. In fact only 59% of respondents claimed to have CO₂ monitors in their bedrooms. All the households who expressed an interest in participating in the long term monitoring were contacted to check that this was the case. In a small number of instances occupants had been mistaken, confusing Carbon Monoxide (CO) and CO₂ monitors, as well as heating controls and CO₂ monitors. Some of these homes were included in the study as a comparison.

1.8 Key findings from the survey were:

• 59% of respondents reported the presence of a CO₂ monitor installed in bedrooms.
• Of those households who have CO₂ monitors installed, only 30% had received advice on how to use the CO₂ monitor.
• The survey found an increase in reported window opening (27% in living rooms and 36% in bedrooms), when compared to the results of the 2014 survey (around 19% in living rooms and around 12% in bedrooms).
• The survey found a significant increase in reported trickle vent opening (75% in living rooms and 69% in bedrooms), when compared to the results of the 2014 survey (around 25% in living rooms and around 28% in bedrooms).
• The main drivers for ventilation include thermal comfort (26% in both living rooms and bedrooms), indoor air quality or "fresh air" (33% in living rooms and 40% in bedrooms) and energy consumption (26%).
• Of those households who have CO₂ monitors installed, 60% stated that they use the monitors and 80% reported taking action when CO₂ levels are high. For action, the majority open the windows but still a minority misunderstood the purpose of a CO₂ monitor (some believed it was a carbon monoxide detector or heating control).

1.9 The 57 households identified were contacted to verify suitability and willingness to participate in the project. By January 2022, monitoring commenced in 16 homes as part of WP3.

• The long term monitoring component of this study (WP3) began in winter 2022 on 16 homes. The ventilation audit undertaken in these homes, included testing mechanical systems and found that extraction rates below government recommendation (13 homes), insufficient door undercuts (9 homes), unclear labelling of switches (6 homes), systems turned off (8 homes), and lack of ventilation advice (12 homes). Reported issues with mechanical systems were noise, draughts, costs of running.
• Long term monitoring (WP3) began in Winter 2022 on 16 homes. Seasonal analysis took place and data analysis during winter and spring evidenced 6 homes with indication of poor indoor air quality throughout the dwelling, despite the presence of CO₂ monitors in some of the bedrooms.
• In terms of measured air quality in the homes that were provided with CO₂ monitors (12 out of 16), seasonal means of CO₂ concentration during occupied hours in both living rooms and bedrooms in winter, spring were above 1000 parts per million (ppm) (see WP3-Chapter 5). Whilst it may be concluded that not all homes with CO₂ monitors installed maintain indoor concentrations below 1000 ppm, the underlying causes of this were driven more by the ventilation provision and compliance.
• For temperatures, it was found that during July 2022, several homes reported excessively high temperatures. In two homes occupied by vulnerable people, living room temperatures exceeded 26°C for more than 60-70% of the time. In bedrooms, overheating assessment against TM59-criterion-2^[1] showed overheating on 8 homes out of 16.

1.10 Following initial data analysis of the winter season, 9 households were selected out of the 16 homes for detailed indoor air quality (IAQ) monitoring (WP4) that took place in April 2022 (see Chapter 6 for details). All of the dwellings under the detailed monitoring regime have TVOC levels that would be considered to be relatively low. There was no indication of PM levels being generated from external sources, but was more positively correlated with periods where cooking was likely to be taking place.

1.11 The industry workshop (WP5) explored possible causes of the lack of compliance regarding installation of CO₂ monitors in August 2022. Whilst there is an indication of confusion about CO alarm/ CO₂ monitors in some local authority verifiers, it was identified that a high proportion of homes, primarily owner-occupied homes, may have been subject to stage warrants for pre 2015 Standards. This was verified in the 4 homes (those with no CO₂ monitors) out of 16 that were monitored, where the building warrant was submitted before 1 October 2015 for homes built in 2019.

1.12 The survey had identified a lack of advice to householders as part of the handover information about how to use the CO₂ monitors and the workshop identified limitations on this. During the workshop the need for providing ventilation advice gradually, i.e. after occupants were settled in the homes, was also discussed.

1.13 A concern raised at the time of the introduction of the revised standards is that it may result in widespread complaints from occupants (i.e. complaints relating to a presumed energy consumption from the CO2 monitor, visual disturbance, or any generic mistrust from having this equipment in bedrooms). The feedback from the workshop and elsewhere is that this has not been the case. Given the earlier evidence of user interventions, it may be concluded that the overall effect has been positive.

1.14 The overall conclusions are broadly as follows:

• There is increased awareness of issues of ventilation and health. This may have been due to a general increase of interest, but the Covid-19 pandemic may also have impacted on awareness and behaviour. Underlying health issues among occupants (especially respiratory diseases such as asthma as well as chronic obstructive pulmonary disease) were also important drivers for ventilation awareness, as evidenced from the household survey
• Whilst the survey indicated that, compared to the 2014 research, there is a greater awareness of the importance of ventilation, including of air quality as a driver for ventilation. Though, many of the barriers to effective ventilation remain, which includes issues of noise and security. Thermal comfort and energy use remain the main drivers for window opening and closing.
• There was evidence of the use of the CO₂ sensors in homes as a catalyst for ventilation behaviours and raising awareness for occupants and there were no significant unintended consequences identified. Their continued use in regulations is supported. However, this could be further supported by better provision of advice about their purpose, and effective use of ventilation systems
• Issues of compliance remain the significant barrier. A large proportion of the homes tested, did not meet minimum Building Standard requirements but it was also clear that house builders have the tendency to submit greater than normal levels of applications before changes in Building Standards come into effect to avoid having to build to the new standards for as long as possible.
• These issues were the predominant drivers for incidences of poor ventilation identified during the long-term monitoring, which remain commonplace.