indoor air quality

The purpose of this summary is to review Air Infiltration and Ventilation Centre activities, as reflected in its publications, related to indoor carbon dioxide over the 40 years that have transpired since its creation. These activities, like most applications of indoor CO2 to the fields of ventilation and indoor air quality, have focused on the following: control of outdoor ventilation rates, i.e., demand control ventilation; use as a tracer gas to measure outdoor air change rates; providing an indicator or metric of IAQ; and, directly impacting human health, comfort and performance.

Indoor pollutants and particles pose a threat to human health as people spend 90% of their time in indoor spaces. A proper ventilation system should be able to remove indoor air pollutants, reduce particle depositions, at the lowest energy consumption by that system. In this work, particle concentrations and depositions are presented for two ventilation configurations (1) Displacement Ventilation (DV) and (2) the conventional ceiling supply and return.

To date, the vast majority of indoor air quality studies have relied on repeated visits to dwellings to obtain data derived from short-term monitoring exercises, a time-consuming process that places considerable constraints on personnel, equipment and costs. These studies have focussed on the use of research-grade instrumentation; however, recent developments in the field of consumer-grade indoor air quality sensor technology offers new opportunities.

Ventilation is critical in interpreting indoor air quality (IAQ), yet few IAQ assessments report ventilation rates; even when they do, the measurement method is often not fully described. Most ventilation assessments use a tracer gas test (TGT) to measure total air change rate. In a TGT, the indoor air is marked with an easily identifiable gas (tracer) so that the air change rate can be inferred by monitoring the tracer’s injection rate and concentration.

Infiltration is an uncontrolled contribution to ventilation in a building and can contribute significantly to the total ventilation rate, particularly in older, leaky, dwellings which can rely on infiltration to provide adequate indoor air quality. However, as explored in this paper, using a whole house airtightness metric to characterise ventilation rates can fail to identify low ventilation rates in specific rooms. 

Guaranteeing high indoor air quality and high degree of user satisfaction at the same time is one of the challenges when improving the energy efficiency of a building. Current non-residential buildings mainly use mechanical ventilation systems to ensure high air quality. Mechanical ventilation systems are known for minimising heat losses but at the same time lead to higher installation, operating and maintenance costs. Furthermore, mechanically conditioned rooms may lead to the sick building syndrome caused by the lack of operable windows.

This study aims to assess the indoor thermal and environmental quality of low-income households in New South Wales, Australia. It adds evidence-based findings on the performance of residential buildings and contributes to improving the indoor environmental quality of social housing. The research presented in this paper involved subjective and objective evaluation of indoor air and environmental quality.

Mixed-mode ventilation uses intelligent switching between natural and (partly) mechanical ventilation modes to find the best possible balance between indoor air quality, user comfort and energy consumption. It applies demand-control at the level of the operating mode depending on the constraints imposed by the building, its users and its surroundings. Although mixed-mode ventilation is said to have the potential to achieve a comfortable and healthy indoor environment while achieving significant energy savings, it is rarely used in practice.

Buildings account for approximately 40 % of energy use in the European Union, as well as in the United States. In light of the European Energy performance of buildings directive, efforts are underway to reduce this energy use by targeting zero or nearly zero energy buildings. In such low energy buildings in cold climates, ventilation to ensure suitable indoor air quality is responsible for half or more of their energy use. The use of heat recovery and demand-controlled ventilation are potential solutions to reduce ventilation-related energy consumption.

This study is a first large-scale analysis of the performance of a cloud connected and smart residential mechanical extract ventilation (MEV) system based on field data. About 350 units were analysed over a period of 4 months from December 2018 up to March 2019, corresponding with the main winter period in Belgium. Half of the units were installed as a smartzone system which means additional mechanical extraction from habitable rooms as bedrooms.