Current contribution to IIEQ (%)
1. Indoor Environmental Quality Index (IIEQ)
Real-time insights on the indoor environmental quality index
Indoor Environmental Quality (IEQ) refers to the overall condition of a building's indoor environment, encompassing factors such as air quality, thermal comfort, lighting, and acoustics.
The Indoor Environmental Quality Index (IIEQ) quantifies these factors on a scale from 0 (very poor) to 100 (excellent), offering a clear and comprehensive measure of how indoor conditions support occupants' health, comfort, well-being, and productivity—key indicators of building performance and sustainability.
Why It Matters: Through this Digital Twin Platform, different stakeholders can monitor and improve the IEQ to create indoor spaces that promote well-being, productivity, and long-term sustainability. Poor indoor conditions can lead to fatigue, discomfort, reduced cognitive performance, and even health issues such as headaches or respiratory problems. Conversely, environments with high IEQ scores enhance concentration, satisfaction, and overall human performance. By leveraging the digital twin's continuous monitoring capabilities in real time, building managers and occupants can make data-driven decisions that support healthier, more comfortable, and energy-efficient environments—transforming buildings into truly human-centered spaces.
The IIEQ is calcualted using the following weighted equation [1]: IIEQ=0.285 ITC+0.35 IIAQ+0.195 IAC+0.17 IIL, where ITC, IIAQ, IAC, and IIL represent thermal comfort, indoor air quality, acoustic comfort, and indoor illumination, respectively.
The graph below show the historic IIEQ value and the % contribution of the different IEQ indeces (IIEQ), offering actionable insights to maintain and enhance overall indoor quality.
[1] Mujan, I., Licina, D., Kljajić, M., Čulić, A. and Anđelković, A.S., 2021. Development of indoor environmental quality index using a low-cost monitoring platform. Journal of Cleaner Production, 312, p.127846. DOI: 10.1016/j.jclepro.2021.127846.
2. Indoor Air Quality Component Index (IIAQ)
Real-time insights on the indoor air quality index
The Indoor Air Quality Component Index (IIAQ) provides a real-time evaluation of indoor air conditions by considering the following parameters:
- CO2 Levels: Indicating ventilation effectiveness and buildup of stale air (optimal < 800 ppm, acceptable up to 1000 ppm).
- Total Volatile Organic Compounds (TVOC): Representing chemical pollutants from materials and products (optimal < 0.087 ppm, acceptable up to 0.261 ppm) [2].
- Particulate Matter (PM2.5): Measuring fine particles that can affect respiratory health (optimal < 9 µg/m³, acceptable up to 25 µg/m³).
The IIAQ is calculated using the highest percentage of dissatisfied (PPD) value among these factors, following the formula IIAQ = 100 – max(PPD(CO2), PPD(VOC), PPD(PM2.5). This method ensures the index reflects the most critical air quality issue at any given moment. Maintaining these parameters within their optimal ranges supports healthier, safer, and more comfortable indoor environments for learning and working.
[2] Sensor Thresholds, Atmocube Sensors. Accessed on November 11, 2025. Atmocube Support.
3. Indoor Thermal Comfort Component Index (ITC)
Real-time insights on the indoor thermal comfort index
The Indoor Thermal Comfort Component Index (ITC) provides a real-time assessment of how well indoor environments support occupant thermal comfort. It is based on the Predicted Mean Vote (PMV) model, as defined by the ANSI/ASHRAE Standard 55-2023[3], which evaluates comfort considering not only temperature, humidity, and air velocity, but also clothing insulation and metabolic activity levels.
- Temperature Levels: Ideally maintained between 21–24 °C in winter and 23–26 °C in summer.
- Humidity Levels: Optimal 40–60%, preventing discomfort from dry or overly humid air.
- Air Velocity: Recommended below 0.15–0.20 m/s in occupied zones to avoid drafts. In this case it is assumed to be 0.1 m/s.
- Clothing Insulation (Clo): Reflects the thermal resistance of clothing; typically around 0.5–1.0 clo for trousers and shirts. For typical ensembles of trousers and short-sleeve shirts, the insulation value is 0.57 clo.
- Metabolic Rate (Met): Represents activity level; standard indoor activities such as studying or office work are around 1.0–1.2 met. In this case assumed to be 1.1 met (sedentary office work or light activity)
The ITC is derived from the percentage of dissatisfied (PPD) occupants related to thermal comfort, using the formula ITC = 100 – PPD, where higher values indicate more favorable comfort conditions. This integrated index ensures that deviations in any thermal factor are promptly detected, enabling proactive adjustments to maintain a healthy, energy-efficient, and comfortable indoor environment.
[3] American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). (2023). ANSI/ASHRAE Standard 55-2023, Thermal environmental conditions for human occupancy. Appendix B. American National Standards Institute. ANSI Webstore.
4. Indoor Acoustics Comfort Component Index (IAC)
Real-time insights on the indoor acoustics comfort index
The Indoor Acoustics Comfort Component Index (IAC) provides a real-time evaluation of acoustic comfort by assessing indoor background noise levels against a defined design threshold. Excessive noise can negatively impact concentration, communication, and overall well-being, making acoustic comfort an essential aspect of indoor environmental quality.
- Background Noise Levels: Continuous monitoring of ambient sound to ensure it remains within acceptable limits for comfort and productivity. In this case, the design noise level is set at 40 dB, representing an optimal acoustic condition for learning and working spaces.
The IAC is derived from the Predicted Percentage of Dissatisfied (PPD) with acoustic conditions, estimating the share of occupants affected by excessive noise. It is calculated using the formula IAC = 100 – PPD, where higher scores indicate better acoustic comfort. This approach enables proactive monitoring and management of sound conditions to maintain quiet, comfortable, and productive indoor environments.
5. Indoor Visual Comfort Component Index (IIL)
Real-time insights on the indoor visual comfort index
The Indoor Visual Comfort Component Index (IIL) provides a real-time evaluation of lighting conditions within indoor environments. It assesses how illumination levels support comfort, visual performance, and well-being by ensuring adequate brightness for various activities.
- Illumination Levels (Lux): Monitoring light intensity to maintain illumination within optimal ranges for comfort and productivity—typically 300–500 lux for classrooms and office spaces.
The IIL is derived from the Predicted Percentage of Dissatisfied (PPD) with lighting conditions, using the formula IIL = 100 – PPD, where higher scores indicate better visual comfort. Continuous monitoring enables proactive adjustment of lighting conditions to maintain bright, comfortable, and energy-efficient indoor environments.
