What indoor environmental quality data should you monitor?
For many building owners, facilities managers and estates teams, indoor environmental quality is becoming a more important part of how building performance is judged. Occupants are more aware of comfort, air quality and wellbeing than they were in the past, and many clients now want better visibility of what conditions are actually like inside their buildings.
The challenge is that once monitoring is being considered, the next question is often which data is actually worth collecting. There is no shortage of sensors or dashboards available, but more data does not automatically mean better understanding.
The most useful indoor environmental quality data is the data that helps a client understand how spaces are performing, where conditions may be affecting comfort or usability, and what practical action may be needed. In other words, the aim is not to collect as much information as possible. It is to collect the right information for the building and the way it is used.
Start with the conditions that most affect occupants
For most buildings, the most useful starting point is the environmental information that has the biggest influence on comfort and perceived air quality.
That typically means temperature, humidity, CO2 and lighting levels. These data types often provide the clearest first view of whether spaces are being heated, cooled, ventilated and lit in a way that broadly supports their use.
Temperature data helps show whether areas are consistently too warm, too cold or unstable. Humidity data can help identify spaces that feel stale, dry or uncomfortable, and can sometimes highlight wider issues with ventilation or moisture conditions. CO2 data is commonly used as an indicator of how well occupied spaces are being ventilated relative to how they are being used. Lighting level data can help show whether spaces are appropriately lit for the tasks being carried out and whether lighting conditions are consistent across the area.
For many buildings, these are the core data points that provide the most practical value.
Temperature should be monitored properly, not assumed
Temperature is one of the most basic environmental measurements, but it is also one of the most important.
Many comfort complaints ultimately come down to spaces being too hot, too cold or fluctuating more than they should. The problem is that without reliable data, those complaints are often difficult to assess properly. Building teams may know that an area is uncomfortable, but not whether the issue is persistent, time-specific, localised or linked to the way the controls are operating.
Monitoring temperature helps move the conversation from opinion to evidence. It can show whether the problem is real, when it occurs, how often it occurs and whether it is linked to plant operation, occupancy or layout changes.
This is especially important in refurbished spaces, where the way an area is actually used may no longer match the original controls design.
Humidity provides useful context
Humidity is sometimes overlooked, but it can add important context to temperature and air quality data.
A space may have a reasonable temperature while still feeling uncomfortable because the humidity level is too high or too low. In some buildings, humidity can also help identify issues with ventilation performance, moisture risk or changing conditions in occupied areas.
From a client’s point of view, humidity data is often most useful when viewed alongside temperature rather than on its own. Together, they provide a more rounded picture of how an environment is likely to feel to the people using it.
CO2 is one of the most useful indicators in occupied spaces
CO2 is one of the most commonly used indoor environmental quality measurements, particularly in offices, meeting rooms, classrooms and other regularly occupied spaces.
It is not a direct measure of air quality in the widest sense, but it is a very useful indicator of how occupancy and ventilation are interacting. In simple terms, if CO2 levels rise consistently in a space, it can suggest that ventilation is not keeping pace with how the area is being used.
This makes CO2 data especially useful where occupancy varies throughout the day, where layouts have changed, or where there are ongoing complaints about stuffiness, poor concentration or rooms feeling uncomfortable. It can also help support better decisions around scheduling, ventilation review and local plant operation.
Lighting levels can be just as important as thermal conditions
Lighting is an important part of the indoor environment, but it is often left out of monitoring discussions.
In practice, lighting levels can have a significant effect on comfort, usability and how suitable a space feels for the people working in it. Areas that are too dim, unevenly lit or overlit can affect concentration, user satisfaction and the overall quality of the space. Monitoring lighting levels can help identify where conditions do not match the intended use of the area, particularly in offices, meeting rooms, circulation spaces and refurbished environments where layouts may have changed.
Lighting data can also be useful when considered alongside occupancy patterns and space use, helping clients understand whether lighting provision and control still reflect how the building is actually being used.
Consider where air quality or particulates are relevant
In some buildings, it may also be useful to monitor additional air quality indicators, such as particulate matter or other environmental factors, depending on the type of building and what the client is trying to understand.
This is more likely to be relevant where there are specific concerns about internal air conditions, external pollution influence, high-occupancy spaces or buildings with more sensitive users. Not every building needs this level of detail, but where there is a clear reason for it, these additional measurements can provide useful insight.
The important thing is to monitor them for a practical reason, not simply because the technology allows it.
Think about how the building is really being used
Indoor environmental quality data becomes much more useful when it reflects the way the building is actually occupied.
This is particularly important in office environments, where spaces are often refurbished on a speculative open-plan basis before a tenant is in place, then later reconfigured with partitions, meeting rooms, cellular offices or changes in occupancy density. If those changes are not reflected in the controls strategy, environmental conditions can quickly become uneven or difficult to manage.
The same issue appears in many other types of building. Rooms may be used differently from how they were originally designed, occupancy patterns may have changed, and local plant may be serving spaces in ways that no longer fit the layout. Monitoring indoor environmental conditions in the right locations helps identify those mismatches.
In practice, good data is not just about what you measure, but where and why you measure it.
What clients usually want to know
From a client’s perspective, the main question is usually not what can be monitored, but what will actually be useful.
Most clients want data that helps them understand whether spaces are comfortable, whether ventilation is broadly appropriate, whether complaints are supported by evidence and whether building conditions are aligned with how the space is being used. They also want to know whether the monitoring will help identify practical improvements rather than simply create more information to look at.
That is why the best indoor environmental quality monitoring strategies are usually quite focused. They aim to provide clear and useful insight rather than a large volume of low-value data.
A sensible starting point for most buildings
For many buildings, a practical starting point is to monitor:
- temperature
- humidity
- CO2
- lighting levels
- occupancy or space use data where it helps explain conditions
- selected additional air quality indicators where there is a clear need
That will not be the full answer for every site, but it is often enough to provide a strong first picture of how spaces are performing and whether further action is needed.
Good IEQ data should support action
The value of indoor environmental quality data is not in the dashboard itself. It is in what the data allows the building team to do.
Good data can help identify poorly performing spaces, support ventilation review, explain recurring comfort complaints, highlight areas affected by layout changes and create a better basis for control adjustments or optimisation. It can also help support wider reporting around occupant wellbeing and environmental performance where that is relevant.
In simple terms, the data should help the building team understand conditions more clearly and respond more confidently.
Final thought
The most useful indoor environmental quality data is the data that helps explain how spaces feel, how they are performing and whether the building is supporting the people using it in the way it should.
For most buildings, that means starting with temperature, humidity, CO2 and lighting levels, then adding further monitoring only where there is a clear reason to do so. The aim should always be to collect information that is practical, relevant and capable of supporting action.
In simple terms, a building should monitor the indoor environmental data it can actually use.
Need help deciding what indoor environmental data would be most useful for your building?
If you want better visibility of indoor conditions and a clearer understanding of how spaces are performing, we can help review your site and identify the most practical monitoring approach.
