United States of America

The modelling of air flows to investigate indoor air quality and energy issues has been a topic at the AIVC for all of its 40 years. Models have been developed that range in complexity from single-zone algebraic expressions that can be calculated by hand to complex multi-zone approaches that integrate contaminant transport and other functions.

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.

This study used a mathematical model to explore the accuracy of extrapolating multi-point blower door test results down to lower pressures at which building infiltration usually occurs naturally.  The mathematical model was applied to leaks of five different widths.  The leakage of the five different widths was then combined in different distributions to simulate total building leakage.  The calculated total building leakage was then compared to an extrapolation from the test pressures using a power law curve fit.

As newer homes are being built tighter than the existing housing stock, questions have been raised about the concentrations of pollutants of concern in new homes and how mechanical ventilation systems can address this issue. This study measured pollutants of concern in 70 new homes with mechanical ventilation in California, USA and compared the results to a previous study of home without mechanical ventilation. The key pollutants were measured using both time-integrated and time-resolved over a one-week period and included formaldehyde, PM2.5 and NO2.

The estimation of low-rise, residential building infiltration rates using envelope airtightness values from whole building fan pressurization tests has been the subject of much interest and research for several decades, constituting a major topic of discussion during the early years of the AIVC. A number of empirical and model-based methods were developed, with their predictive accuracy evaluated in field studies around the world.

Indoor carbon dioxide (CO2) concentrations have been used for decades to evaluate indoor air quality (IAQ) and ventilation. However, many of these applications reflect a lack of understanding of the connection between indoor CO2, ventilation rates and IAQ. In particular, a concentration of 1800 mg/m3 (1000 ppmv) has been used as a metric of IAQ and ventilation without an appreciation of its basis or application.