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What does it mean to have “good indoor environmental quality”?
Systemair unpacks the building blocks that contribute to good indoor environmental quality
Indoor Air Quality
Many factors contribute to personal and collective ideas on having a good indoor environment quality (IEQ). The senses serve as a basis for occupants' input, which can be affected by light, drought, pollution, temperature, humidity, emissions, etc.
A good indoor environment considers all parameters that can affect occupants' senses.
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The temperature
In the same room, it is no surprise that one person can feel comfortable, while another might feel discomfort. Everyone has their own ideal temperature. Temperature is often the primary reason people feel discomfort, which can be affected by clothing and surface temperatures. According to several investigations into the matter, no matter how ideal the conditions of a room's indoor environment, 5% of the people will always be dissatisfied.
To the left you can see the predicted percentage dissatisfied when temperature varies from the average ideal temperature.
In addition to disrupting occupants' comfort levels, temperature also significantly impacts performance and productivity, which underscores the need to control and manage room temperatures effectively.
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The Air Quality
Air quality is challenging to measure. The most common way to do it is by looking at CO2 concentration. Volatile Organic Compounds (VOCs), organic chemicals with a high vapour pressure at ordinary room temperature, also contribute to air quality and are measured differently. VOCs' high vapour pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air, a trait known as volatility. VOCs are numerous, varied, and ubiquitous. They include both human-made and naturally occurring chemical compounds, and most scents or odours stem from VOCs.
The Air Velocity
The throw length defined from a diffuser at 0.2 m/s in terminal velocity is commonly mentioned. The definition serves as a standard for manufacturers to have a common base when discussing the performance of a product. In the occupied zone (0.1 – 1.8 m above floor), the most common velocity requirements are 0.25 m/s during winter and 0.15 m/s during the summer.
Under this definition, there are also two other factors called CLO (clothing) and MET (metabolism).
CLO is the insulation ability of clothes to provide good comfort in a given condition. In wintertime, we usually set CLO-value to 1. In summer, it is set to 0.8.
MET depends on the person's activity level and can be found in tables for different types of work or activities.
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Sound and light pollution
Sound and light pollution or emissions in the daily environment also critically impact individuals comfort and wellbeing in a given space. The amount of and tolerance to pollution varies depending on the environment. A person inside a shopping mall can probably accept a higher sound level than in the bedroom. For sound, the typical range can be between 30 to 40 dB(A).
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Humidity
Humidity has a significant impact on occupants' health. If humidity is too low or too high, individuals can have adverse reactions. The "ideal" humidity conditions for humans can be between 40 - 60%, depending on the indoor temperature. Various geographic locations can have high or low humidity, which can be considered comfortable or uncomfortable conditions. In general, if indoor air has low humidity or is considered "too dry", this negatively affects the human mucous system. Having too high humidity indoor can result in a risk of mould in the indoor environment.
Chillers in ventilation systems can take care of some of the dehumidification of outdoor air with high humidity.
Summary
To summarise, a good indoor environment considers all parameters that can affect occupants' senses, including air quality and thermal, acoustic, and visual climate. Together, these factors determine whether an environment is comfortable and conducive to working, learning and living. It is critical to understand individuals' different needs and their ideas about what makes a good climate. Lastly, there must be a move to emphasise innovations that empower people better to control the conditions in their spaces.