Building standards - ventilation guidance: research

2. Research outline

The overall purpose of this work is:

2.1 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.

Specific objectives include:

2.2 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. To provide a comparison of performance of post change performance against pre-change performance.

2.3 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.

2.4 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.

2.5 To provide clear robust and justified evidence underpinning the outcomes from the work in the required formats to best fit the needs of the clients.

Progress on the agreed work packages is described below.

WP1

2.6 This was an initial project setup phase, including an initial meeting with the client organisation to refine the scope, timescales, deliverables, and to set up and procure the following work packages. The WP also undertook a literature review to identify best practice, emerging trends in this field, and other regulatory standards.

2.7 This stage confirmed the key research questions, a refinement of the methodology in relation to this, and identification of timescales and deliverables over the course of the project. This WP has been completed and the literature review is contained in Appendix 1. The project timescale has been significantly affected by the impacts of the COVID pandemic and these are described in the following section.

WP2

2.8 This WP2 (household survey) is aimed to gather data about occupant's awareness of their ventilation provision, use of the CO₂ indicators and how this affects their air quality. The objective was to gather this through a general survey of 200 homes built to the 2015 regulations.

2.9 The survey was based on the questionnaire used in the 2014 study of Occupant Interactions with Ventilation^[2], and the 2018 dMEV study^[3]. This allows some longitudinal comparison of responses, for example to identify changes in awareness. This survey included occupancy patterns, building information and use, awareness of ventilation systems, the frequency of use of these systems, awareness of indoor environmental conditions, and barriers and drivers for use of ventilation. The survey preparation included the development of additional survey content to address the specific questions raised in this study concerning use of CO₂ sensors and consequent interaction with ventilation provision, including mechanical and natural systems. This included awareness of the sensors, how it affects household ventilation behaviours, value of the alert systems and unintended or negative consequences.

2.10 The survey was developed and agreed with Building Standards Division (BSD) in Spring 2021. Following the methodology used in the 2014 study, the intention was to deliver this through a face-to-face doorstep survey, however we did identify that this could be undertaken as an online, postal or telephone survey, with some refinement of the questionnaire.

2.11 The team commissioned a professional survey company to undertake the survey. Based on similar research, this required identification of approximately 800 addresses of suitable homes. After the scoping exercise in WP1 we identified the requirements for representation of responses in the study, for example dwelling types, construction systems, ventilation provision, geographical location, and tenure type. The team used existing contacts with developers and housing associations to identify suitable sites for the survey. The original intention was to conduct these on a limited series of selected developments which would make the survey and the monitoring much simpler and reduce the number of other variables in the survey. We identified 5 housing developments, which represented typical construction types and common ventilation provision.

2.12 The ongoing restrictions in the Spring of 2021 prevented the survey being carried out at that time. Given on-going limitations, and different behavioural patterns of home use and ventilation in the summer, it was agreed the survey would be postponed to the end of August 2021 for two reasons; firstly, a survey about ventilation in the summer months may give a skewed picture and secondly an expectation that restrictions would be relaxed by the Autumn. However, this was not the case and the research company which was bound by the requirements of the Market Research Society (MRS) was not able to conduct face to face surveys.

2.13 Given the pressure on time, after consultation with BSD and negotiations with the survey company, it was decided to change the mode of delivery to a postal survey, with possible face-to-face follow-up when this was possible. As a postal survey has a lower rate of return (approximately 10:1) so a larger number of addresses were required. To facilitate this, we used a dataset provided by BSD that included addresses of properties with certification in 2019 and 2020.

3 Selection Criteria:

2.14 This dataset was very large with 38057 addresses in the sample, so some selection was undertaken to narrow this down. This included using the 2019 addresses as these would be beyond a defects liability period and occupants would have settled in; location in the central belt; inclusion of both houses and flats, but exclusion of some less common typologies such as bungalows and maisonettes. It also excluded properties larger than 100m² on the grounds that larger homes are less likely to be adversely affected by poor ventilation issues. Selection criteria consisted of:

• Certification in 2019
• Central Belt Location: Postcodes E, ML, PA1 and G
• Houses and flats
• Excluded Detached Houses and Bungalows, Maisonettes,
• Total Floor Area (TFA) <100m²

2.15 This provided 2525 sample addresses for use in the survey, and this was used as the basis for the survey delivery and headline results of this are reported in Section 3. The survey was sent out at the end of August 2021. One of the disadvantages of a postal survey is that it takes longer for returns to be collected with returns coming in over September and October. This had a knock-on effect for the identification of homes for participation in the monitoring study in WP3. By November 115 returns had been achieved and so measures were put in place to undertake face to face surveys. The Housing Associations for these sites had agreed to contact the occupants ahead of the survey when this was first planned for August, and for the later survey, these communications had to be re-established. Further face-to face surveys were commenced in late November and were on-going. Unfortunately, the emergence of the Omicron variant resulted in the MRS withdrawing face to face survey permissions. After consultation with BSD, it was agreed that rather than waiting for these restrictions to be lifted, the remainder of the survey would be conducted as a postal survey – we have used the Housing Association addresses for these as they are likely to produce better returns. By February 2022 there are 138 surveys completed with 57 households that had expressed interest in participating in the long monitoring. The results of the survey to date are provided in Section 3.

WP3

2.16 The aim of WP3 is to undertake actual monitoring of environmental conditions in homes to investigate what effects the new regulations have had on actual ventilation use. The survey in WP2 had included a question to ask the respondents if they would be willing to participate in a monitoring programme.

2.17 As outlined in the previous section, the slower response rate to the survey meant that availability of locations was also slower to materialise, and this delayed the deployment of the monitoring installation. Part of the initial discussions in WP1 had identified general parameters for investigation, for example, comparison of homes who do or do not make use of the systems; or those that do use the systems, which may then compare effectiveness in different construction types or with different ventilation provision and it was agreed that this would be refined from the survey data.

2.18 A key issue arose in an initial analysis of the survey returns in that a high proportion (37%) indicated that they did not have a sensor or were unsure (7%). The properties that had expressed an interest were followed up by telephone and these responses were tested, but it would appear that they were reliable. After consultation with BSD, it was agreed that some houses without CO₂ sensors would be included in the monitoring study. Whilst the main aim is to test effectiveness of the use of the sensors, these properties may provide comparator sites for evaluation. The deployment of the detailed monitoring is described in more detail in Section 4 but at the time of writing (April 2022) 16 homes are being monitored.

2.19 Although the monitoring has commenced much later than planned, with it running to August 2022, we are confident that reliable data from the winter, spring and summer seasons will provide a robust picture of environmental condition in these homes.

2.20 The installation also included the collection of further data about the homes. This included verification of the construction and ventilation system, testing of the mechanical ventilation provision, identification of undercuts, and verification of patterns of occupancy. The outline findings for this and sample data are shown in Section 4.

2.21 At the end of March 2022 the detailed monitoring study began (WP4) to capture detailed data on a time-limited period. A total of 3 weeks of intense monitoring are capturing more granular data on occupancy and behaviour. The locations of these homes were identified through analysis of the long term monitoring, with a focus – but not exclusively - on homes that appear to be poorly ventilated. Specific sensors system is been employed, will focus on the presence of particulates (PM₁₀) and tVOCs.

2.22 WP5 was intended to gain an understanding of the industry awareness and application of the 2015 requirements. This included collection of insights from 48 members of the industry sector, including designers, contractors and building control officers. The results of the household survey (WP2) have been the basis to conduct a focus group that was conducted in August 2022 online to explore more detail how guidance is being interpreted by designers, the design solutions being implemented, design methodologies being used. One new issue that has been explored in the light of findings to date was about ensuring compliance and guidance for users.

2.23 WP6 is the work package for preparation of written reports and findings for BSD and related agencies, collation of interim reports, production of a final report and wrap up workshop for BSD