Conference Agenda

During the COVID-19 pandemic, public spaces have been identified as major sites for airborne transmission, especially in densely occupied and poorly ventilated spaces. In Belgium, many public spaces are still insufficiently ventilated and need to be equipped with a ventilation system. However, economic factors and technical constraints hinder the implementation of ventilation systems in practice. There is thus a need for practical and cost-efficient solutions that are easier to integrate in existing buildings and retrofit projects.

The aim of this study was to identify innovative ventilation systems and strategies that address economic and technical constraints, while taking into account the specific needs of public spaces and health aspects.

An economic study was conducted with specialized engineering offices for different settings (restaurant, concert venue,…) to evaluate the cost-effectiveness of these solutions compared to standard ventilation systems. Additionally, Computational Fluid Dynamic (CFD) simulations were used to assess IAQ performance, including airborne transmission in the presence of a contagious occupant.

The results indicate that several innovative ventilation solutions are relevant alternatives for existing buildings. For example some systems are based on alternative ventilation strategies with mechanical exhaust in occupied spaces rather than supply. Others are based on the combination of a basis system and a boost system for temporarily higher capacity. In this paper, one of these solutions is presented. Depending on the context and performance requirements, these solutions are cost-effective and easier to implement in existing buildings while ensuring sufficient IAQ. Therefore, these innovative solutions show substantial potential to support the deployment of ventilation systems in existing public spaces, improving IAQ in alignment with the objectives of Belgium’s recent regulation.

London’s public ground transport provides a basis for sustainable metropolitan mobility, widely depended on as an accessible and energetically efficient alternative to the mass usage of private vehicles. Many communities rely on public transport for essential mobility, but what this entails is the regular occupancy of contained and often crowded passenger cabins. Collective urban transport was quickly identified as an environment with one of the highest rates of COVID-19 propagation. Buses especially did not have the mechanical or power capacity to ventilate at rates advised for safer buildings in early COVID guidance. In May 2021, window blocks were deployed on buses across all fleets, aiming to maximise ventilation and mitigate the build-up of exhaled bioeffluents.

This study investigates the efficacy of window blocks as a ventilation strategy by monitoring concentrations of metabolic CO2 inside the cabin to understand prolonged passenger exposure to exhaled breath. The dataset presents CO2 and temperature measurements from 15 fully operational buses over a span of 5 months (August to December 2022), providing high-resolution insight into the quality of ventilation provision in urban buses in reaction to seasonal climatic variation. The raw data was refined using actual routing times and delays to exclude idle periods. CO2 data was analysed to track peak concentrations and assess whether window blocks reduced the frequency of prolonged periods of poor air quality (e.g. during rush hours).

The results show that partially open windows can pose challenges to the vehicle's heating/cooling units, creating difficulties in maintaining thermal comfort. This moreover increases energy consumption for air conditioning and heavily reduces vehicle range for electric buses due to excessive power demand. Striking a balance between well-ventilated, temperature-controlled cabins is essential for thermal comfort, air quality, and energy efficiency. This research informs the development of bus ventilation standards, ensuring passenger comfort and well-being.

Objective

The acoustic environment is one of the important IEQ elements, and some office rooms continuously measure equivalent A-weighted sound pressure levels. If the amount of carbon dioxide exhaled and the amount of virus are correlated, sound pressure level measuring can be used assuming the ventilation rate, thus reducing the risk of human-derived infectious diseases.

The objective of this study is to develop a simple method for assessing ventilation rate related to infection risk by estimating carbon dioxide exhalation rates based on equivalent sound levels in addition to carbon dioxide measurement.

Method

A multiple regression analysis was employed to predict the ventilation rate using equivalent sound level, conversation time, and the difference between indoor and outdoor carbon dioxide concentration as explanatory variables.

Results

The adjusted determination coefficient was 0.7713, and the significance probability based on variance analysis was p=0.0634, indicating that a certain degree of prediction was possible.

The number of suspended particles is reduced by ensuring an appropriate ventilation volume. The relationship between the average equivalent noise level and the number of particles removed per hour for each particle size was also examined. The correlation for particle sizes of 0.5 to 1.0 micrometer was found to be relatively high (the correlation coefficient was 0.658 for particles between 0.5 and 1.0 micrometer, and 0.680 for particles between 1.0 and 3.0 micrometer ).

Conclusion

As the equivalent sound level is not solely dependent on speech, our intention is to pursue further research in order to assess the risk of infection accurately. This will entail an expansion of the factors affecting carbon dioxide concentration in the air, including the determination of whether windows are open and ventilated, and the use of the equipment's equivalent sound level, season, and outside temperature as variables.

Post-pandemic, the importance of indoor air quality (IAQ), particularly in mitigating infectious aerosols, has grown significantly. In Ontario, with 4,850 schools and approximately 280.6 million square feet of building space, schools have implemented strategies to reduce viral transmission and create safer environments for students and staff. Among the most common measures are ventilation and filtration, with MERV 13 and HEPA filters commonly suggested by school boards and policymakers. However, the installation of these filters in older schools presents challenges due to infrastructure limitations, potential overload of electrical systems, and increased operational costs. In this study, we present an innovative solution: silver-graphene oxide treated MERV-A 9-A (M9AZG) filters, treated with silver-graphene oxide, which offer superior protection against infectious aerosols while being compatible with existing HVAC systems. These filters have lower pressure drops (resistance to airflow) compared to most MERV 13 filters, resulting in significant energy savings.

A pilot study at McKinnon Park Secondary School in Caledonia, Ontario, replaced existing MERV 13 (CM13) filters with M9AZG filters in two air handling units (AHUs), one providing ventilation to the gym and the other the cafeteria. The results showed that M9AZG filters achieved 22% energy savings due to lower pressure drops, reducing operational costs. In Infection Risk Management Mode (IRMM), due to M9AZG’s higher pathogen removal efficiency, thus requiring less outdoor air intake. The estimated annual energy savings in the gym and cafeteria were 5.86 and 18.11 kWh/ft2 respectively These savings translate to 5.62 tonnes of CO2eq in the gym and 16.37 tonnes in the cafeteria annually. The extended filter life of M9AZG filters further reduces waste and resource consumption. This solution offers schools an efficient, cost-effective way to improve IAQ for infectious aerosols and energy efficiency without major infrastructure upgrades, contributing to healthier learning environments and long-term sustainability.

The COVID-19 pandemic brought building ventilation into the focus of public health. Low ventilation rates increased respiratory infection rates. Ventilation in ASHRAE climate zone 5A directly impacts energy use due to the extremely cold winters and warm-humid summers. This paper assesses the spatial, energy, and HVAC needs of ventilation upgrades for five major school types in an Iowa school district. The schools were selected based on time and type of construction, location and orientation of classrooms, and type of HVAC system. Recent ASHRAE Standard 62.1 – 2016 for Ventilation for Acceptable Indoor Air Quality required a combined outdoor air rate of 6.7 L/s/p or 14.2 CFM/p based on the default occupant density in classrooms (age 9 plus). A revised ‘Minimum Fresh Air Rate per Person’ (MFApP) of at least 20 L/s/p or 42.4 CFM/p is recommended by ASHRAE 241 – 2023. To determine the necessary building operations changes for these increased MFApP rates, thermal models were developed in the energy simulation tool ClimateStudio for one classroom per school. ClimateStudio uses a preset MFPApP rate of 4.72 L/s/p or 10 CFM/p based on ASHRAE 62.1 - 2022, which was compared to 6.7 L/s/p or 14.2 CFM/p and 20 L/s/p or 42.4 CFM/p with respect to annual and seasonal building energy consumption. The pressure drops across the ductwork were assessed in the current HVAC systems to understand if ducts and fan motors could handle these increased ventilation rates. The results reveal that as MFApP rates increase, site EUI increases by up to 30% for the highest CFM/p depending on the system. In most cases ductwork and fan motors would need to be replaced to continue efficiency and keep noise levels low. This paper thus assesses energy use and HVAC systems impact of improved ventilation rates to allow effective dedication of retrofit funds.