Airbase publication

Building energy behaviour and indoor environmental conditions have been changing due to different external events that have been taking place at global level from 2020, from the COVID pandemic (2020-2022) to the energy crisis (mainly from the war in Ukraine from February 2022). During these events, existing naturally ventilated (NV) buildings have had to balance minimum thermal comfort, high levels of ventilation (to reduce CO2 concentration and risk of infection) and the lowest energy costs.

The world has experienced the devastating nature of airborne transmitted diseases through the COVID-19 pandemic. Significant actions were taken in order to reduce the number of new infections, such as quarantines, social distancing, mask wearing, frequent hand washing and surface disinfection. However, all these measures have proven insufficient to eradicate short and long-range infections, confirming the need for engineering tools to control the indoor air quality.

The offer of air cleaners has increased significantly since the SARS-CoV-2 pandemic. However, it is not clear to what extent they can contribute to indoor air quality. There are multiple standards that describe test methods for air cleaners, but no consensus can be found on how to determine the performance of the air cleaners.

The COVID-19 pandemic increased the awareness and importance of infectious pathogens as contaminant in the indoor air, especially for non-residential buildings with a high occupational density like schools. During the COVID-19 pandemic air cleaning is often proposed as mitigation strategy for infectious risk in these types of buildings. However, indoor air quality (IAQ) in general comprises of a large range of possible contaminants and factors that can equally impact the health, comfort and well-being of occupants.

Coughing is one of the most important respiratory activities for air transmitted pathogens. It is essential to understand the dispersion of exhaled particles when coughing to improve the prevention measure and reduce the cross-infection risk. However, cough flow structure is complex and influenced by many parameters. Simplifications are often made to the initial flow condition when simulating the transport of particles expelled during coughing in laboratory or numerical studies .

Some airborne pathogens can infect susceptible people over long distances in buildings when they are transported in small respiratory particles suspended in the air. The pathogen concentration in air can be decreased using engineering controls, such as ventilation, filtration, or inactivation. To determine their effect, it is common to use the Wells-Riley model to estimate the probability that a susceptible person is infected and is a function of the dose of infectious pathogen received and a Poisson distribution.

On June 24, 2023, ASHRAE approved the publication of Standard 241-2023 Control of Infectious Aerosols. The purpose of Standard 241 is “to establish minimum requirements for control of infectious aerosols to reduce risk of disease transmission in the occupiable space” of buildings by defining “the amount of equivalent clean airflow necessary to substantially reduce the risk of disease transmission during infection risk management mode”.

Accounting for inter- and intra-personal differences requires individual and cohort comfort models. For their development, emulators for thermal sensation of occupants are needed. Physiological signals can be acquired using both wearable and contactless devices. However, due to the widespread availability of sensing methods it is difficult to select the proper measuring method for the application.

Most current environmental control systems installed in buildings aim to create a uniform IEQ, disregarding the large interpersonal and intrapersonal variability in occupants’ thermal, visual, acoustics & air quality requirements. By creating occupant micro-environments that respond to individual preferences, and relaxing the surrounding space, personalized environmental control systems (PECS) can satisfy all occupants with relatively low-energy input.

Personalized Environmental Control Systems (PECS) have advantages of controlling the localized environment at occupants’ workstation by their preference instead of conditioning an entire room. A new IEA EBC Annex (Annex 87 - Energy and Indoor Environmental Quality Performance of Personalised Environmental Control Systems) has recently started to establish design criteria and operation guidelines for PECS and to quantify their benefits. This topical session will provide an introduction to the objective/scope, activities, and intended outputs of the annex.