The measurement of indoor environmental quality (IEQ) and the responsible management of resulting data is fundamental not only to control the building services systems, but also to assess and improve the opportunities for success in creating safe and responsible built environments.
This CPD will draw selectively on the recently published Technical Memorandum 68 Monitoring indoor environmental quality (TM68), and will specifically focus on the guidance on the ethical approach to measurement and monitoring of built environments, as well as the increasingly challenging task of responsible data collection and management.
The much misattributed and misquoted adage ‘If you can’t measure it, you can’t manage it’ provides a suitably succinct reminder of the need for a robust and appropriate sensing, monitoring and data management regime for building services systems. There has been much written about the ‘performance gap’, and there are increasingly urgent demands on building operators to moderate energy usage, operational costs and environmental impact while maintaining safe and healthy built environments.
The publication of the new TM68 is, therefore, a particularly well-timed addition to the CIBSE catalogue. Although the TM does not profess to be an encyclopaedic reference, it effectively provides an excellent framework by covering key requirements for environmental measurement, monitoring and associated data management in buildings. (Much of this article is based on abstracted and abbreviated text taken from the TM – for more complete detail, see the TM, freely downloadable for CIBSE members.)
TM68 provides an overview of how data collected in real buildings can convey meaningful information about IEQ by providing primers on current technologies and recommendations. It notes that ‘priority has been given to factors that directly impact occupants’ comfort and wellbeing’. The initial chapter provides a summary of the most important issues to be considered before embarking on an IEQ monitoring project, such as stakeholders’ involvement, ethical considerations and privacy issues, among others.
The following four chapters – thermal comfort, air quality, luminous quality, and acoustic quality – examine units and performance metrics, available instruments and sensors, practical sampling considerations, and real-life case studies. These four chapters are not considered further in this article – which is not to diminish their importance or the quality of the work, but simply in order to focus on some of the more novel aspects covered in the TM.
The final chapter of the TM provides a rare contextualisation for built environment professionals of continuous sensing systems and data management – this will be explored in more detail later in this article.
For those who are research active, the potential impact of measurement on building occupants has long required a formal assessment prior to any activity being undertaken. The TM gives an early airing to ethical issues that, historically, may not have been seen as relevant to, or previously given the priority by, practising building services engineers as much as they are today.
It is contended that the pervasiveness of measurement possible with new technologies – especially imaging, wearables and so-called internet of things (IoT) devices – gives rise to concerns about surveillance such that it should be considered alongside or before the technical considerations, perhaps as part of the goal-setting and expectation-management process.
The TM cites various legislative and guiding instruments that provide a base line for good practice, noting the reasonable expectation to meet or exceed these requirements. The legislative tools typically focus on fundamental aspects of privacy, such as obtaining consent, data use and storage, and other practices typically known as ‘data management’. Elements of a good data management plan are noted as including:
- Clear consent gathering
- Secure transfer and storage
- Appropriate use of different data streams
- Limiting usage of data to the purposes set out in the original consent statements
- Secure and timely deletion of data, whether on request or upon expiry of consent or expected term.
A rule of thumb is suggested that when data are traceable to a person or record, any aspects of a person – such as medical history, preferences or feedback – they must be handled with more care and security than, say, environmental data. This might mean restricted access, automatic deletion or expiry, better encryption, or other measures.
Although the TM suggests that designers and specifiers of buildings and systems cannot reasonably be held responsible for enforcing ethical limits on clients and data users, it notes that the specifier is obliged to ensure that both the design of the system and the documentation contain guidance and reasonable safeguards against misuse.
An area of the TM that truly catches the zeitgeist – and one that is likely to stretch the knowledge envelope for many professionals in the built environment – is addressed in the extensive final chapter, which considers the management of continuous sensing systems and their data. It describes recommendations and best practices for collecting and using data gathered from sensors and meters in and around buildings, focusing on the practicalities of – and issues associated with – data collection from operational buildings.
The TM recommends that the building services engineer should plan for the ways in which protocols (the standardised rules that allow successful transmission of information between devices), systems and standards for data exchange interact with each other, how the data can be made easily accessible, and how they ultimately influence their own workflows or those of other building managers. It suggests that the decision-making process for specifying a sensing system should follow a process familiar to building services engineers, as in Figure 1.
The frequency with which measurements are taken and/or the spatial density of sensors determine the resolution, or granularity, of measurement. More spatial coverage means more hardware, and a greater frequency of collection requires more data to be transmitted, stored and analysed.
Approaches – such as varying the resolution at various times or for a particular building use – will depend on how closely a measurement must resemble the ‘true’ parameter values, and the resulting impact on the proper operation of a building. The TM highlights that there are no fixed rules on the number of data points or frequency of measurement.
In any case, if the measurement system is not integrated into building workflows it is unlikely that the data gathered will influence the actions of building managers and users, so a growing trend is to gather and integrate multiple data streams from around a building into a single accessible resource.
Retrofitting novel IoT-based continuous monitoring systems may be more challenging in existing buildings that may have previously not included any regular data collection. The benefits of aggregating such data can include the ability to control existing heating, ventilation and air conditioning (HVAC) systems using measurements from several IEQ sensors; providing holistic input for predictive maintenance; and automatically reporting to post-occupancy evaluation tools.
Measured environmental data will normally require post-processing that might include cleaning (removing out of range values); transforming (scaling or shifting data); and rounding, truncation or conversion. As illustrated in Figure 2, there is a limit to how much smoothing and cleaning is useful, and an overzealous procedure could obscure a genuine problem that produces an extreme, but valid, measurement and so, for some investigations, raw data may be preferred.
A prerequisite of data management is data security. This is examined in detail in the CIBSE Digital Engineering Series1 of publications but is covered briefly in the TM, including a list of measures to increase resilience to common cyber-security issues.
Measures to increase cyber-security resilience
- End-to-end encryption of data
- Reduction of personally identifiable data collected
- Safe deletion of personal data after reasonable use
- Stronger authentication process for manager or administrator users
- Limited remote access to data and control or administration systems
- Removal of rights for departed employees and contractors
- Ensure data service providers hold and process data to appropriate information security standards
Data are most usable when properly and systematically labelled and encoded, and while an installer may be able to systemically specify names and labels for a new system, there may already be existing systems that contain data about a building, such as the building automation and control system (BACS) or BIM models.
There may also be existing middleware – software that mediates between different software and systems – that offers the opportunity for easier integration using standard components. Compatibility with existing data sources can significantly improve the value of the measured data.
IEQ measurement systems increasingly store and analyse data employing applications hosted in remote ‘cloud’ infrastructure. The data would normally be stored in databases that include the recently applied ‘time series’ databases, which enable continuous and efficient storage and processing of large amounts of real-time data organised in time-value pairs. Data should normally only be stored if they will be used at some point, and reasons for storing data for an extended time may include:
- Looking at long-term trends
- Novel methods and analyses made possible by large datasets
- Comparison of performance across several years
- Benchmarking across different building types
- Future research opportunities.
There may be client requirements for data to stay on site or within a certain jurisdiction because of security concerns, and data may need to be deleted after a reasonably short period to reduce the possibility of being nefariously used to gather intelligence.
Offsite storage and analysis, especially when hosted on the public cloud, will ease the display, sharing and analysis across multiple interfaces and access points. A BACS may still be a local processor for the data – displaying, analysing and controlling systems based on measured data – but cloud-based systems can significantly expand the opportunity for reporting, certification, or multi-building analysis.
There are opportunities to reduce data transfer, throughput and storage with the use of so-called ‘edge computing’, where sensing tools and local communication devices interpret raw data and transmit only the information that is relevant to a human user or BACS.
For example, an ‘intelligent’ camera could analyse images to determine the number of people in a given space and only transmit this value back to the cloud, without retaining the source image. This can help alleviate privacy concerns, reduce the data transfer, and so reduce data storage. Many sensors/devices now include integrated data logging and networking to enable direct connection to the web.
Systems – particularly cloud-based – can self-diagnose and provide alerts or health indicators in real time. However, performance and reliability will be improved with maintenance, systems redundancy, regular testing, and inspection.
The TM provides an overview of common technologies and protocols for data collection from IEQ sensors, noting that the best protocol for a continuous monitoring system will depend on the sensing devices being used, existing communication infrastructure, and the extent of acceptable intervention or disruption.
Each protocol offers advantages and disadvantages in terms of cost, limits on coverage and granularity, and reliability. Data can also be served directly by a sensing device, or using protocols such as building automation and control network (BACnet) over wired, wireless or physical internet protocol (IP) ethernet connections.
It is important to ensure that the data are usable and ‘fresh’ – delivered to a server or user at the correct time. There are a multitude of vendors and protocols for systems that measure indoor environmental conditions, where data are collected by a continuous measurement system and either passed to a cloud server before being pulled back down by other systems, or exchanged by the hardware on site.
Onsite compatibility of systems would entail sharing of communication hardware so that data are available from multiple systems without going through the cloud. This can be achieved by the building manager or owner themselves, either by using industry-standard protocols such as BACnet, hardware ‘bridges’ (physical devices that can communicate with sensors from different vendors), software drivers or middleware, or some combination of these.
An advantage offered by some modern IoT protocols, such as LoRa (from ‘long range’) illustrated in Figure 3, is that in theory the communication hardware provided by any manufacturer can be used to transmit the data from sensors made by any other manufacturer.
Two systems that use the same protocol may not necessarily ‘talk’ to each other automatically, but may instead need middleware or drivers. Open APIs (simplified, openly available software links between applications) allow IEQ measurement systems to be connected to existing building automation systems without the need for specialist drivers or hardware.
Most system providers will deliver (serve) data in common formats through an API (which would require proper security authentication) allowing building management teams to interrogate and store data on their own servers, databases and spreadsheets.
Once data are collected at a site, they must be typically transmitted to a cloud database (known as ‘backhauling’) – the TM discusses wired versus wireless backhauling – plugging into a physical wired network, and the use of existing IT systems compared with a physically separate network.
This article has provided a flavour of TM68 that the foreword suggests ‘aims to provide a starting point for all building professionals’, and it would appear a worthwhile investment for any building professional to take the time to discover, or refresh, knowledge in this fundamental technology that underpins the success, or failure, of built environments.
- Digital Engineering Series, CIBSE bit.ly/CJJan23CPD1