Building standards - ventilation guidance: research

9. Recommendations

9.1. In terms of the key research question, the study found clear examples of benefits derived from the provision of the CO₂ sensors, including increased awareness of air quality and use of the sensors to inform ventilation behaviours. There was no evidence seen of negative impacts, in terms of increased complaints. It is therefore recommended that the provision of CO₂ sensors should be maintained. The monitoring indicated that poor ventilation remains prevalent in bedrooms, but there were also instances of poor ventilation in other occupied rooms. A limitation in bedrooms is that the insights are retrospective as occupants are generally asleep, so opportunities for interaction are limited. Expanding their use to other rooms such as living rooms, where interaction may be more likely, would potentially increase opportunities for interaction. This may also have benefits in terms of providing occupants with information to balance heating and ventilation.

9.2. Clearer guidance is required for ventilation in general and the CO₂ sensors specifically to enable more informed use. There was limited evidence of use of quick-start guides, and the nature and timing of advice provision requires consideration.

9.3. The study found evidence of poor compliance with regulations. These included delays to the implementation of standards, poor compliance with performance standards for ventilation provision, the lack of provision of CO₂ monitors in bedrooms, and associated guidance to occupants.

9.4. A key issue is that of non-compliance and related to that maintenance of compliance. More robust measures are clearly needed to ensure that the minimum standards are delivered at hand-over, but also consideration of how these standards may be maintained over time, recognising that under the building standards system, there is limited scope for action to be enforced post acceptance of the completion certificate.

9.5. At present the scope of powers available under the building standards system is the submission of the completion certificate, beyond which there is limited scope for action. Given the widespread nature of non-compliance, a requirement to make good, that is to meet the standard may not be a sufficient driver for action. Punitive measures for non-compliance may act as a catalyst for improved compliance.

9.6. The evidence provided by this research shows that there are some areas for improvement in the ventilation provision. It is suggested to provide minimal revisions to the guidance supporting Standards to provide a protocol for ventilation induction and follow up to improve occupant understanding and ability to interact effectively with the ventilation strategy employed within their home.

9.7. Problems with on-going maintenance of ventilation systems was identified. Whilst at present regulations cannot mandate onward maintenance, the introduction of a requirement to provide a maintenance plan may be helpful. Further recommendation for providers would be a requirement for regular servicing of mechanical systems, mirroring the one currently being adopted for boilers.

9.8. In this study the prevalence of new dwellings with an EPC provided in 2019, but being built to pre 2015 standards, suggest that latitude to enable industry to adopt to new standards may be being used to avoid these unnecessarily. This could delay governmental efforts to improve buildings in terms of energy demand (and associated CO2 emissions) and heath for residents of Scottish homes. Measures may therefore be required to reduce the lag time between building warrant submission and actual construction to avoid homes being built today under the building standards of 5 years ago.

9.9. There was little evidence of occupant knowledge of the standards to which their homes had been built, so a requirement for this information to be made available, may also act as a driver to faster adoption of new standards. New build dwellings should have information or certification provided to owners and occupants about the Standards to which they are constructed to evidence 'new' buildings built to superseded standards – this could potentially be incorporated into Quickstart Guides.

Further research

9.10. External conditions may be major drivers for ventilation use in homes. This may include detrimental external conditions such as noise or pollution and there has not been any research that attempts to measure indoor and outdoor pollutants or other nuisances concurrently.

9.11. Related to this are strategies for ventilation in rural areas of Scotland where external weather and moisture is a major issue and practices of ventilation are influenced and at time restricted by it. The limitations of this study were the relatively restricted geographical location of homes, and lack of external contextual data which may be relevant.

9.12. Currently mandated mechanical ventilation systems are based on standard assumptions of occupancy for moisture control. There is little information on loads derived by different types of occupancy (for example larger households, family with young children, or people with special needs) that may result in higher moisture loads, which may present challenges for existing systems. An understanding of the performance envelope of systems may be useful as a means of determining risks.

9.13. The use of MVHR as an energy efficient ventilation system is becoming more established, but there is little data on their longer term effectiveness, particularly in more mainstream housing (i.e. not Passivhaus). Related to this may be investigations of alternative strategies, for example demand control driven systems.

9.14. Research to underpin the appropriateness of ventilation systems to cope with an increased demand for ventilation during heatwaves. This links to the new Mandatory Standard "3.28 Overheating risk" introduced on 1 February 2023. Here, the Simple method for assessing and mitigating overheating recommends – alongside solar gain control – providing effective ventilation to remove the build-up of heat, indicating that the level of air change sought under standard 3.14 (4 air changes per hour) should cope in a building with cross ventilation, which was not the case in two of the monitored homes.

9.15. Further work may be required to identify the scope of warrant applications prior to implementation of new regulations to provide better data on the scale and impacts of this practice. This may be beneficial in terms of informing Impact Assessments of new regulations and identification of progress toward Government Targets for energy reduction and climate change.