Building standards - ventilation guidance: research

8. Conclusions

8.1. This research gives an insight of the effect the 2015 changes to guidance in Standard 3.14 have had on ventilation design, on occupant interaction and experiences on ventilation systems, on measured indoor quality.

8.2. The first objective was set out to identify to what extent ventilation systems installed following these changes achieve the minimum recommended ventilation performance and where dwellings do not, identify the root cause(s) of this non-compliance.

Ventilation provision and information

8.1. Whilst study cohort had a limited number of properties that were equipped with the sensor, and a smaller number that has information on their use, the study found clear evidence of use of the monitors to help manage ventilation and their inclusion in standards is justified.

8.2. However, the research gives evidence that CO₂ monitors on their own do not constitute a mitigating strategy for healthy indoor environment. Further support is required for the provision of advice on information about the purpose of the sensors, and actions which may be taken to improve ventilation

8.3. The ventilation audit performed in 16 homes show that ventilation design is not adequately provided, providing evidence of compliance issues. The ventilation audit performed in 16 homes found that dMEVs extraction rates below government recommendation (13 homes), insufficient door undercuts (9 homes), dMEV had no clear labelling of switches (6 homes), dMEV systems turned off (8 homes), and lack of ventilation advice (12 homes). Reported issues with dMEV were noise, draughts, costs of running.

8.4. The ventilation audit depicted a landscape of ventilation systems that may not be able to achieve healthy indoor environments. On this premise, the requirement of CO₂ monitors can aid occupants to spot if anything is wrong and manage or ask for advice in the case of council or housing association rented homes.

8.5. To secure an adequate provision of ventilation, ensuring flow paths (trickle vents open, adequate door undercuts and dMEV properly working) has proven to be a challenge. In fact, only 1 out of the 14 homes built to 2015 Standards (within the 16 surveyed homes) met the 2015 standards in their entirety. Moreover, in the few cases where the system did meet standards, the system remains vulnerable to occupants' interaction (dMEV turned off due to noise, undercuts reduced by carpets, trickle vents closed due to drafts). The exception and comparison was the Passivhaus dwelling.

8.6. Whilst this may indicate a benefit of MVHR, other standards of construction and performance are better demonstrated through a Passivhaus approach. During the industry workshop there was discussion of other vulnerabilities that MVHR systems may carry during building use, such as loss of power supply and MVHR maintenance (filter cleaning), with concerns raised that if the industry is unable to provide simple mechanical systems, there may be inherent risks in more complex systems without a more robust compliance and maintenance requirement.

8.7. The long term monitoring component of this study (WP3) illustrates that is still a critical number of homes with sub-optimal conditions in homes. The ventilation survey showed that many dMEV systems were not to specification as well as many were turned off (due to cold and noise concerns). Given that the homes surveyed were built to a standard of airtightness where improved ventilation provision is required (compared to the traditional housing stock) the requirement of CO₂ monitors is further justified and needed.

Implementation of published solutions/guidance

8.8. The second objective was set out to identify how guidance is being interpreted by designers, the design solutions being implemented, design methodologies being used, the performance of these design methodologies in practice including end user perceptions and delivered indoor air and environmental quality, and to identify where potential improvements to guidance are required to deliver robust solutions.

8.9. The large postal survey (WP2) provided suggested an apparent lack of compliance to provide CO₂ monitors in households with them being present on in 59% of the households.

8.10. Further investigation following feedback from the industry workshop (WP5) found that for homes with a 2019 energy certification (EPC, issued on completion), there is no guarantee that the building was constructed to 2015 regulations, as building warrants may have been submitted prior to 1 October 2015 (date of changed to the regulations). In fact, when investigating further the 4 homes under long-term monitoring that did not have CO₂ monitor, the search concluded that for all 4 homes, building warrants were submitted before changes to the Standard. This supports the hypothesis raised during the workshop.

8.11. The change process and development lag for building regulations is known and is identified in any supporting Impact Assessment to provide adequate lead-in time before new requirements are imposed on the construction sector and the practical need to build out projects already submitted/approved. The evidence from the workshop is that this may be used as a cost-saving exercise, and will necessarily impact on the rate of implementation of new standards and consequent Government targets for energy reduction and improvements in ventilation provision. Lack of adoption of new regulations for homes being built up to 4 years after construction seems excessive and measures to reduce or avoid this would therefore be useful. Once aspect of this is that there was no evidence that homeowners were aware of the standards to which their homes had been built, so a requirement for this to be provided may aid transparency.

8.12. The issue of provision of advice was discussed during the industry workshop. The survey has indicated a general lack of advice, on ventilation provision in general and on CO₂ monitors in particular. It was considered that the process to provide technical induction and with it the ventilation advice should be provided at an appropriate time and followed up on. In this respect, the role of the social landlord is potentially major, since they have a direct interest of a two-way communication with tenants for a properly managed home. The private sector instead lacks that continual engagement. However, there was also limited evidence of the use of Quick-start guides observed through the household survey. Whilst in some cases these were provided, as observed through the monitoring setups, they accompanied large amounts of other information provided at hand-over.

Assessing indoor environmental performance in practice.

8.13. The third objective was to establish indoor environmental performance and how this relates to occupant interactions with available means of ventilation, such as trickle ventilators, windows, doors and extract fans in dwellings constructed under the 2015 building regulations and Technical Handbook guidance through: identification of a large sample of representative dwellings, a broad snapshot study of more than 200 to establish system types, occupant perceptions and monitored performance, and perform in-depth monitoring of at least 20 dwellings for a period of 12 months.

Measured indoor quality

8.14. In terms of measured air quality, of the homes that were provided with CO₂ monitors (12 out of 16), the results of peak CO₂ concentrations in both living rooms and bedrooms in winter, spring were above 1000 ppm (see WP3-Chapter 5). Whilst it may be concluded that not all homes with CO₂ monitors installed maintained indoor concentrations below 1000 ppm, the underlying causes of this were driven more by lack of system compliance identified in Section 5.10.

8.15. The results of temperature monitoring indicated instances of overheating in 6 homes during July 2022. There is scope to further examine such homes and the influences of design (layout, orientation, construction materials, etc.) on indoor temperatures but this was not evaluated as part of this work.

8.16. Restating what was found in the literature review, balancing the needs of both energy efficiency and IAQ particularly in small single aspect family flats, may prove to be an intractable problem unless a properly working and well-maintained MVHR system is used. However, given the apparent challenges with implementation of simpler ventilation provision, more robust standards for design, installation, compliance, and-over and maintenance would be required.

8.17. Inefficient ventilation provision was found also in lofts. Even though these are beyond the scope of this research project, mould growth in two of the monitored homes from the same development suggests that constructors and developers are overlooking at these spaces exposing occupants to health hazards. Further research should verify to what British Standard these homes have been constructed. At the moment Section 3.15 Condensation of the Building standards technical handbook 2020: domestic reads: "3.15.3 Control of condensation in roofs. Section 8.4 of BS 5250: 2002 provides guidance on the control of condensation in the principal forms of roof construction. Clause 8.4.1 of BS 5250 lists various issues that should be considered in the design of roofs to reduce the possibility of excess condensation forming that might damage the building and endanger the health of the occupants."^[27] It should be noted that the BS 5250: 2002 has been withdrawn by versions 2011, first, and recently by BS 5250:2021^[28] which requires for vents to be provided on warm roofs. The 2002 document was unretrievable therefore it remains unclear the reason for avoiding the use of roof vents in the affected homes.

8.18. In addition, such short-term monitoring showed no difference in PM levels suggesting that external traffic pollution was not a major factor over the monitoring period.

Occupants' awareness and interaction with their ventilation systems

8.19. The large household survey (WP2) provided comparable insights to a baseline study from 2014. In terms of occupant use of the ventilation systems (windows and trickle vents) a significant improvement in occupant engagement was found, compared to the 2014 study (Sharpe et al. 2014). Specifically, a noticeable increase in reported trickle vent opening was identified (more than double then 2014 study).

8.20. In terms of trickle vent opening frequency, respondents largely (75%-living room and 69%-bedroom) left them open all of the time while a small portion (13% in living room and 12% in bedroom) left them open. This figure is in contrast with the responses obtained during the 2014 study submitted depicting a noticable switch between "open all the time" (around 25%) and "never open (around 60%)".

8.21. This shift in trickle vent opening is not supported by an increase in ventilation advice, which suggests other factors may be at play. In fact, among the drivers for window opening in the bedroom we find a noticeable increase in choices of driver "open for fresh air" in the bedrooms (from less than 5% in the 2014 study to 40% in the current study).

8.22. Since the previous study there may have been a general increase in awareness of ventilation. However the COVID-19 pandemic may also have impacted, with Government and Public Health messaging about the importance of ventilation. The main drivers for ventilation were to provide "fresh air" as one of the main drivers for window opening (40%-bedroom and 33%-living room) and rooms being "too warm" (26% in both bedroom and 3 living room).

8.23. In terms of barriers for ventilation, reasons to not use trickle vents are "noise" (11%-bedroom and 18%-living room), "draughts" (20%-bedroom and 15%-livingroom), and "don't feel the need to" (22%-bedroom and 31%-livingroom). When it comes to windows, the main barriers for window opening are "heat loss" (26% in both bedroom and living rooms) and "noise" (23%-bedroom and 20%-living room).

8.24. From the above, there is some evidence of an increased need to manage indoor air quality. In fact, when asked about their perception of their indoor environment in the household survey, 3% found the quality of the air very poor in bedrooms, when in the previous household survey 2014, this figure was 0%. Although 3% is not a significant increase, when asked "Is there anything that could improve the ventilation in your house?", of the few responses (18) obtained, the majority of responses relate to a need for increased ventilation, whether that is via more air volume or accessible/secure windows (50% of responses).

8.25. Within the survey, of those homes that had a CO₂ sensors, there was a significant proportion (45%) who reported using these sensors at least weekly, and 80% of respondents reporting undertaking activity – primarily window opening – as a result of this. Whilst the size of the study and the underlying issues of compliance means that there is a not a clear demonstration of an effect of this activity, it nevertheless indicates that the introduction of the sensors has increased awareness and interaction, albeit limited by advice and ventilation provision.

Doing research during the pandemic

8.26. As a result of the COVID-19 pandemic, timescales had to be shifted and methods of data collection adapted to accommodate restrictions posed at a national level. That notwithstanding, home occupants showed outstanding interest in the research and trusted researchers' protocols to avoid transmission.